;www.fruitcake.plus.com
;LAST UPDATE: 08.07.2014 savelij
include ../../define.a80
TAP_EMU_BORDER EQU 0
; **************************************
; *** SPECTRUM 128 ROM 1 DISASSEMBLY ***
; **************************************
; The Spectrum ROMs are copyright Amstrad, who have kindly given permission
; to reverse engineer and publish ROM disassemblies.
; =====
; NOTES
; =====
; ------------
; Release Date
; ------------
; 23rd May 2009
; =================
; ASSEMBLER DEFINES
; =================
;TASM directives:
;#define DB .BYTE
;#define DEFW .WORD
;#define DEFM .TEXT
;#DEFINE DEFS .FILL
;#define END .END
;#define EQU .EQU
;#define ORG .ORG
; The Sinclair Interface1 ROM written by Dr. Ian Logan calls numerous
; routines in this ROM. Non-standard entry points have a label beginning
; with X.
ORG $0000
;*****************************************
;** Part 1. RESTART ROUTINES AND TABLES **
;*****************************************
; -----------
; THE 'START'
; -----------
; At switch on, the Z80 chip is in interrupt mode 0.
; This location can also be 'called' to reset the machine.
; Typically with PRINT USR 0.
;; START
L0000: DI ; disable interrupts.
XOR A ; signal coming from START.
LD DE,$FFFF ; top of possible physical RAM.
JP L11CB ; jump forward to common code at START-NEW.
; -------------------
; THE 'ERROR' RESTART
; -------------------
; The error pointer is made to point to the position of the error to enable
; the editor to show the error if it occurred during syntax checking.
; It is used at 37 places in the program.
; An instruction fetch on address $0008 may page in a peripheral ROM
; such as the Sinclair Interface 1 or Disciple Disk Interface.
; This was not however an original design concept and not all errors pass
; through here.
;; ERROR-1
L0008 NOP
JP RST8_CMP
; LD HL,($5C5D) ; fetch the character address from CH_ADD.
; LD ($5C5F),HL ; copy it to the error pointer X_PTR.
; JR L0053 ; forward to continue at ERROR-2.
; -----------------------------
; THE 'PRINT CHARACTER' RESTART
; -----------------------------
; The A register holds the code of the character that is to be sent to
; the output stream of the current channel.
; The alternate register set is used to output a character in the A register
; so there is no need to preserve any of the current registers (HL,DE,BC).
; This restart is used 21 times.
DUPL 0X0010-$,0XFF
;; PRINT-A
L0010: JP L15F2 ; jump forward to continue at PRINT-A-2.
; ---
DUPL ADR_SEL_ROM-$,0XFF
L0014 OUT (C),A
NOP
RET
DUPL 0X0018-$,0XFF
; DB $FF ; this byte is used by the SPECTRUM command in
; ROM 0 to generate an error report "0 OK".
; DB $FF, $FF ; four unused locations.
; DB $FF, $FF ;
; -------------------------------
; THE 'COLLECT CHARACTER' RESTART
; -------------------------------
; The contents of the location currently addressed by CH_ADD are fetched.
; A return is made if the value represents a character that has
; relevance to the BASIC parser. Otherwise CH_ADD is incremented and the
; tests repeated. CH_ADD will be addressing somewhere -
; 1) in the BASIC program area during line execution.
; 2) in workspace if evaluating, for example, a string expression.
; 3) in the edit buffer if parsing a direct command or a new BASIC line.
; 4) in workspace if accepting input but not that from INPUT LINE.
;; GET-CHAR
L0018: LD HL,($5C5D) ; fetch the address from CH_ADD.
LD A,(HL) ; use it to pick up current character.
;; TEST-CHAR
L001C: CALL L007D ; routine SKIP-OVER tests if the character
RET NC ; is relevant. Return if it is so.
; ------------------------------------
; THE 'COLLECT NEXT CHARACTER' RESTART
; ------------------------------------
; As the BASIC commands and expressions are interpreted, this routine is
; called repeatedly to step along the line. It is used 83 times.
;; NEXT-CHAR
L0020: CALL L0074 ; routine CH-ADD+1 fetches the next immediate
; character.
JR L001C ; jump back to TEST-CHAR until a valid
; character is found.
; ---
DB $FF, $FF, $FF ; unused
; -----------------------
; THE 'CALCULATE' RESTART
; -----------------------
; This restart enters the Spectrum's internal, floating-point,
; stack-based, FORTH-like language.
; It is further used recursively from within the calculator.
; It is used on 77 occasions.
;; FP-CALC
L0028: JP L335B ; jump forward to the CALCULATE routine.
; ---
DB $FF, $FF, $FF ; spare - note that on the ZX81, space being a
DB $FF, $FF ; little cramped, these same locations were
; used for the five-byte end-calc literal.
; ------------------------------
; THE 'CREATE BC SPACES' RESTART
; ------------------------------
; This restart is used on only 12 occasions to create BC spaces
; between workspace and the calculator stack.
;; BC-SPACES
L0030: PUSH BC ; save number of spaces.
LD HL,($5C61) ; fetch WORKSP.
PUSH HL ; save address of workspace.
JP L169E ; jump forward to continuation code RESERVE.
; --------------------------------
; THE 'MASKABLE INTERRUPT' ROUTINE
; --------------------------------
; This routine increments the Spectrum's three-byte FRAMES counter
; fifty times a second (sixty times a second in the USA ).
; Both this routine and the called KEYBOARD subroutine use
; the IY register to access system variables and flags so a user-written
; program must disable interrupts to make use of the IY register.
;; MASK-INT
L0038: PUSH AF ; save the registers.
PUSH HL ; but not IY unfortunately.
LD HL,($5C78) ; fetch two bytes at FRAMES1.
INC HL ; increment lowest two bytes of counter.
LD ($5C78),HL ; place back in FRAMES1.
LD A,H ; test if the result
OR L ; was zero.
JR NZ,L0048 ; forward to KEY-INT if not.
INC (IY+$40) ; otherwise increment FRAMES3 the third byte.
; now save the rest of the main registers and read and decode the keyboard.
;; KEY-INT
L0048: PUSH BC ; save the other
PUSH DE ; main registers.
IF BAS48_ONLY=1
CALL L02BF
ELSE
CALL L386E ; Spectrum 128 patch: read the keypad and keyboard
; in the process of reading a key-press.
ENDIF
L004D: POP DE ;
POP BC ; restore registers.
POP HL ;
POP AF ;
EI ; enable interrupts.
RET ; return.
; ---------------------
; THE 'ERROR-2' ROUTINE
; ---------------------
; A continuation of the code at 0008.
; The error code is stored and after clearing down stacks,
; an indirect jump is made to MAIN-4, etc. to handle the error.
;; ERROR-2
L0053: POP HL ; drop the return address - the location
; after the RST 08H instruction.
LD L,(HL) ; fetch the error code that follows.
; (nice to see this instruction used.)
; Note. this entry point is used when out of memory at REPORT-4.
; The L register has been loaded with the report code but X-PTR is not
; updated.
;; ERROR-3
L0055: LD (IY+$00),L ; store it in the system variable ERR_NR.
LD SP,($5C3D) ; ERR_SP points to an error handler on the
; machine stack. There may be a hierarchy
; of routines.
; to MAIN-4 initially at base.
; or REPORT-G on line entry.
; or ED-ERROR when editing.
; or ED-FULL during ed-enter.
; or IN-VAR-1 during runtime input etc.
JP L16C5 ; jump to SET-STK to clear the calculator
; stack and reset MEM to usual place in the
; systems variables area.
; and then indirectly to MAIN-4, etc.
; ---
DB $FF, $FF, $FF ; unused locations
DB $FF, $FF, $FF ; before the fixed-position
DB $FF ; NMI routine.
; ------------------------------------
; THE 'NON-MASKABLE INTERRUPT' ROUTINE
; ------------------------------------
; There is no NMI switch on the standard Spectrum.
; When activated, a location in the system variables is tested
; and if the contents are zero a jump made to that location else
; a return is made. Perhaps a disabled development feature but
; if the logic was reversed, no program would be safe from
; copy-protection and the Spectrum would have had no software base.
; The location NMIADD was later used by Interface 1 for other purposes.
; On later Spectrums, and the Brazilian Spectrum, the logic of this
; routine was reversed.
;; RESET
DUPL 0X0066-$,0XFF
L0066 NOP
; PUSH AF ; save the
PUSH HL ; registers.
LD HL,($5CB0) ; fetch the system variable NMIADD.
LD A,H ; test address
OR L ; for zero.
; JR NZ,L0070 ; skip to NO-RESET if NOT ZERO
JR Z,L0070
JP (HL) ; jump to routine ( i.e. L0000 )
;; NO-RESET
L0070 POP HL ; restore the
POP AF ; registers.
RETN ; return to previous interrupt state.
; ---------------------------
; THE 'CH ADD + 1' SUBROUTINE
; ---------------------------
; This subroutine is called from RST 20, and three times from elsewhere
; to fetch the next immediate character following the current valid character
; address and update the associated system variable.
; The entry point TEMP-PTR1 is used from the SCANNING routine.
; Both TEMP-PTR1 and TEMP-PTR2 are used by the READ command routine.
;; CH-ADD+1
L0074: LD HL,($5C5D) ; fetch address from CH_ADD.
;; TEMP-PTR1
L0077: INC HL ; increase the character address by one.
;; TEMP-PTR2
L0078: LD ($5C5D),HL ; update CH_ADD with character address.
X007B: LD A,(HL) ; load character to A from HL.
RET ; and return.
; --------------------------
; THE 'SKIP OVER' SUBROUTINE
; --------------------------
; This subroutine is called once from RST 18 to skip over white-space and
; other characters irrelevant to the parsing of a BASIC line etc. .
; Initially the A register holds the character to be considered
; and HL holds its address which will not be within quoted text
; when a BASIC line is parsed.
; Although the 'tab' and 'at' characters will not appear in a BASIC line,
; they could be present in a string expression, and in other situations.
; Note. although white-space is usually placed in a program to indent loops
; and make it more readable, it can also be used for the opposite effect and
; spaces may appear in variable names although the parser never sees them.
; It is this routine that helps make the variables 'Anum bEr5 3BUS' and
; 'a number 53 bus' appear the same to the parser.
;; SKIP-OVER
L007D: CP $21 ; test if higher than space.
RET NC ; return with carry clear if so.
CP $0D ; carriage return ?
RET Z ; return also with carry clear if so.
; all other characters have no relevance
; to the parser and must be returned with
; carry set.
CP $10 ; test if 0-15d
RET C ; return, if so, with carry set.
CP $18 ; test if 24-32d
CCF ; complement carry flag.
RET C ; return with carry set if so.
; now leaves 16d-23d
INC HL ; all above have at least one extra character
; to be stepped over.
CP $16 ; controls 22d ('at') and 23d ('tab') have two.
JR C,L0090 ; forward to SKIPS with ink, paper, flash,
; bright, inverse or over controls.
; Note. the high byte of tab is for RS232 only.
; it has no relevance on this machine.
INC HL ; step over the second character of 'at'/'tab'.
;; SKIPS
L0090: SCF ; set the carry flag
LD ($5C5D),HL ; update the CH_ADD system variable.
RET ; return with carry set.
; ------------------
; THE 'TOKEN TABLES'
; ------------------
; The tokenized characters 134d (RND) to 255d (COPY) are expanded using
; this table. The last byte of a token is inverted to denote the end of
; the word. The first is an inverted step-over byte.
;; TKN-TABLE
L0095 DC "?" ;DB '?'+$80
DC "RND" ;DEFM "RN"
;DB 'D'+$80
DC "INKEY$" ;DEFM "INKEY"
;DB '$'+$80
DC "PI" ;DB 'P','I'+$80
DC "FN" ;DB 'F','N'+$80
DC "POINT" ;DEFM "POIN"
;DB 'T'+$80
DC "SCREEN$" ;DEFM "SCREEN"
;DB '$'+$80
DC "ATTR" ;DEFM "ATT"
;DB 'R'+$80
DC "AT" ;DB 'A','T'+$80
DC "TAB" ;DEFM "TA"
;DB 'B'+$80
DC "VAL$" ;DEFM "VAL"
;DB '$'+$80
DC "CODE" ;DEFM "COD"
;DB 'E'+$80
DC "VAL" ;DEFM "VA"
;DB 'L'+$80
DC "LEN" ;DEFM "LE"
;DB 'N'+$80
DC "SIN" ;DEFM "SI"
;DB 'N'+$80
DC "COS" ;DEFM "CO"
;DB 'S'+$80
DC "TAN" ;DEFM "TA"
;DB 'N'+$80
DC "ASN" ;DEFM "AS"
;DB 'N'+$80
DC "ACS" ;DEFM "AC"
;DB 'S'+$80
DC "ATN" ;DEFM "AT"
;DB 'N'+$80
DC "LN" ;DB 'L','N'+$80
DC "EXP" ;DEFM "EX"
;DB 'P'+$80
DC "INT" ;DEFM "IN"
;DB 'T'+$80
DC "SQR" ;DEFM "SQ"
;DB 'R'+$80
DC "SGN" ;DEFM "SG"
;DB 'N'+$80
DC "ABS" ;DEFM "AB"
;DB 'S'+$80
DC "PEEK" ;DEFM "PEE"
;DB 'K'+$80
DC "IN" ;DB 'I','N'+$80
DC "USR" ;DEFM "US"
;DB 'R'+$80
DC "STR$" ;DEFM "STR"
;DB '$'+$80
DC "CHR$" ;DEFM "CHR"
;DB '$'+$80
DC "NOT" ;DEFM "NO"
;DB 'T'+$80
DC "BIN" ;DEFM "BI"
;DB 'N'+$80
; The previous 32 function-type words are printed without a leading space
; The following have a leading space if they begin with a letter
DC "OR" ;DB 'O','R'+$80
DC "AND" ;DEFM "AN"
;DB 'D'+$80
DC "<=" ;DB $3C,'='+$80 ; <=
DC ">=" ;DB $3E,'='+$80 ; >=
DC "<>" ;DB $3C,$3E+$80 ; <>
DC "LINE" ;DEFM "LIN"
;DB 'E'+$80
DC "THEN" ;DEFM "THE"
;DB 'N'+$80
DC "TO" ;DB 'T','O'+$80
DC "STEP" ;DEFM "STE"
;DB 'P'+$80
DC "DEF FN" ;DEFM "DEF F"
;DB 'N'+$80
DC "CAT" ;DEFM "CA"
;DB 'T'+$80
DC "FORMAT" ;DEFM "FORMA"
;DB 'T'+$80
DC "MOVE" ;DEFM "MOV"
;DB 'E'+$80
DC "ERASE" ;DEFM "ERAS"
;DB 'E'+$80
DC "OPEN #" ;DEFM "OPEN "
;DB '#'+$80
DC "CLOSE #" ;DEFM "CLOSE "
;DB '#'+$80
DC "MERGE" ;DEFM "MERG"
;DB 'E'+$80
DC "VERIFY" ;DEFM "VERIF"
;DB 'Y'+$80
DC "BEEP" ;DEFM "BEE"
;DB 'P'+$80
DC "CIRCLE" ;DEFM "CIRCL"
;DB 'E'+$80
DC "INK" ;DEFM "IN"
;DB 'K'+$80
DC "PAPER" ;DEFM "PAPE"
;DB 'R'+$80
DC "FLASH" ;DEFM "FLAS"
;DB 'H'+$80
DC "BRIGHT" ;DEFM "BRIGH"
;DB 'T'+$80
DC "INVERSE" ;DEFM "INVERS"
;DB 'E'+$80
DC "OVER" ;DEFM "OVE"
;DB 'R'+$80
DC "OUT" ;DEFM "OU"
;DB 'T'+$80
DC "LPRINT" ;DEFM "LPRIN"
;DB 'T'+$80
DC "LLIST" ;DEFM "LLIS"
;DB 'T'+$80
DC "STOP" ;DEFM "STO"
;DB 'P'+$80
DC "READ" ;DEFM "REA"
;DB 'D'+$80
DC "DATA" ;DEFM "DAT"
;DB 'A'+$80
DC "RESTORE" ;DEFM "RESTOR"
;DB 'E'+$80
DC "NEW" ;DEFM "NE"
;DB 'W'+$80
DC "BORDER" ;DEFM "BORDE"
;DB 'R'+$80
DC "CONTINUE" ;DEFM "CONTINU"
;DB 'E'+$80
DC "DIM" ;DEFM "DI"
;DB 'M'+$80
DC "REM" ;DEFM "RE"
;DB 'M'+$80
DC "FOR" ;DEFM "FO"
;DB 'R'+$80
DC "GO TO" ;DEFM "GO T"
;DB 'O'+$80
DC "GO SUB" ;DEFM "GO SU"
;DB 'B'+$80
DC "INPUT" ;DEFM "INPU"
;DB 'T'+$80
DC "LOAD" ;DEFM "LOA"
;DB 'D'+$80
DC "LIST" ;DEFM "LIS"
;DB 'T'+$80
DC "LET" ;DEFM "LE"
;DB 'T'+$80
DC "PAUSE" ;DEFM "PAUS"
;DB 'E'+$80
DC "NEXT" ;DEFM "NEX"
;DB 'T'+$80
DC "POKE" ;DEFM "POK"
;DB 'E'+$80
DC "PRINT" ;DEFM "PRIN"
;DB 'T'+$80
DC "PLOT" ;DEFM "PLO"
;DB 'T'+$80
DC "RUN" ;DEFM "RU"
;DB 'N'+$80
DC "SAVE" ;DEFM "SAV"
;DB 'E'+$80
DC "RANDOMIZE" ;DEFM "RANDOMIZ"
;DB 'E'+$80
DC "IF" ;DB 'I','F'+$80
DC "CLS" ;DEFM "CL"
;DB 'S'+$80
DC "DRAW" ;DEFM "DRA"
;DB 'W'+$80
DC "CLEAR" ;DEFM "CLEA"
;DB 'R'+$80
DC "RETURN" ;DEFM "RETUR"
;DB 'N'+$80
DC "COPY" ;DEFM "COP"
;DB 'Y'+$80
; ----------------
; THE 'KEY' TABLES
; ----------------
; These six look-up tables are used by the keyboard reading routine
; to decode the key values.
; The first table contains the maps for the 39 keys of the standard
; 40-key Spectrum keyboard. The remaining key [SHIFT $27] is read directly.
; The keys consist of the 26 upper-case alphabetic characters, the 10 digit
; keys and the space, ENTER and symbol shift key.
; Unshifted alphabetic keys have $20 added to the value.
; The keywords for the main alphabetic keys are obtained by adding $A5 to
; the values obtained from this table.
;; MAIN-KEYS
L0205: DB $42 ; B
DB $48 ; H
DB $59 ; Y
DB $36 ; 6
DB $35 ; 5
DB $54 ; T
DB $47 ; G
DB $56 ; V
DB $4E ; N
DB $4A ; J
DB $55 ; U
DB $37 ; 7
DB $34 ; 4
DB $52 ; R
DB $46 ; F
DB $43 ; C
DB $4D ; M
DB $4B ; K
DB $49 ; I
DB $38 ; 8
DB $33 ; 3
DB $45 ; E
DB $44 ; D
DB $58 ; X
DB $0E ; SYMBOL SHIFT
DB $4C ; L
DB $4F ; O
DB $39 ; 9
DB $32 ; 2
DB $57 ; W
DB $53 ; S
DB $5A ; Z
DB $20 ; SPACE
DB $0D ; ENTER
DB $50 ; P
DB $30 ; 0
DB $31 ; 1
DB $51 ; Q
DB $41 ; A
;; E-UNSHIFT
; The 26 unshifted extended mode keys for the alphabetic characters.
; The green keywords on the original keyboard.
L022C: DB $E3 ; READ
DB $C4 ; BIN
DB $E0 ; LPRINT
DB $E4 ; DATA
DB $B4 ; TAN
DB $BC ; SGN
DB $BD ; ABS
DB $BB ; SQR
DB $AF ; CODE
DB $B0 ; VAL
DB $B1 ; LEN
DB $C0 ; USR
DB $A7 ; PI
DB $A6 ; INKEY$
DB $BE ; PEEK
DB $AD ; TAB
DB $B2 ; SIN
DB $BA ; INT
DB $E5 ; RESTORE
DB $A5 ; RND
DB $C2 ; CHR$
DB $E1 ; LLIST
DB $B3 ; COS
DB $B9 ; EXP
DB $C1 ; STR$
DB $B8 ; LN
;; EXT-SHIFT
; The 26 shifted extended mode keys for the alphabetic characters.
; The red keywords below keys on the original keyboard.
L0246: DB $7E ; ~
DB $DC ; BRIGHT
DB $DA ; PAPER
DB $5C ;
DB $B7 ; ATN
DB $7B ; {
DB $7D ; }
DB $D8 ; CIRCLE
DB $BF ; IN
DB $AE ; VAL$
DB $AA ; SCREEN$
DB $AB ; ATTR
DB $DD ; INVERSE
DB $DE ; OVER
DB $DF ; OUT
DB $7F ; (Copyright character)
DB $B5 ; ASN
DB $D6 ; VERIFY
DB $7C ; |
DB $D5 ; MERGE
DB $5D ; ]
DB $DB ; FLASH
DB $B6 ; ACS
DB $D9 ; INK
DB $5B ; [
DB $D7 ; BEEP
;; CTL-CODES
; The ten control codes assigned to the top line of digits when the shift
; key is pressed.
L0260: DB $0C ; DELETE
DB $07 ; EDIT
DB $06 ; CAPS LOCK
DB $04 ; TRUE VIDEO
DB $05 ; INVERSE VIDEO
DB $08 ; CURSOR LEFT
DB $0A ; CURSOR DOWN
DB $0B ; CURSOR UP
DB $09 ; CURSOR RIGHT
DB $0F ; GRAPHICS
;; SYM-CODES
; The 26 red symbols assigned to the alphabetic characters of the keyboard.
; The ten single-character digit symbols are converted without the aid of
; a table using subtraction and minor manipulation.
L026A: DB $E2 ; STOP
DB $2A ; *
DB $3F ; ?
DB $CD ; STEP
DB $C8 ; >=
DB $CC ; TO
DB $CB ; THEN
DB $5E ; ^
DB $AC ; AT
DB $2D ; -
DB $2B ; +
DB $3D ; =
DB $2E ; .
DB $2C ; ,
DB $3B ; ;
DB $22 ; "
DB $C7 ; <=
DB $3C ; <
DB $C3 ; NOT
DB $3E ; >
DB $C5 ; OR
DB $2F ; /
DB $C9 ; <>
DB $60 ; pound
DB $C6 ; AND
DB $3A ; :
;; E-DIGITS
; The ten keywords assigned to the digits in extended mode.
; The remaining red keywords below the keys.
L0284: DB $D0 ; FORMAT
DB $CE ; DEF FN
DB $A8 ; FN
DB $CA ; LINE
DB $D3 ; OPEN#
DB $D4 ; CLOSE#
DB $D1 ; MOVE
DB $D2 ; ERASE
DB $A9 ; POINT
DB $CF ; CAT
;*******************************
;** Part 2. KEYBOARD ROUTINES **
;*******************************
; Using shift keys and a combination of modes the Spectrum 40-key keyboard
; can be mapped to 256 input characters
; ---------------------------------------------------------------------------
;
; 0 1 2 3 4 -Bits- 4 3 2 1 0
; PORT PORT
;
; F7FE [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] | [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 0 ] EFFE
; ^ | v
; FBFE [ Q ] [ W ] [ E ] [ R ] [ T ] | [ Y ] [ U ] [ I ] [ O ] [ P ] DFFE
; ^ | v
; FDFE [ A ] [ S ] [ D ] [ F ] [ G ] | [ H ] [ J ] [ K ] [ L ] [ ENT ] BFFE
; ^ | v
; FEFE [SHI] [ Z ] [ X ] [ C ] [ V ] | [ B ] [ N ] [ M ] [sym] [ SPC ] 7FFE
; ^ $27 $18 v
; Start End
; 00100111 00011000
;
; ---------------------------------------------------------------------------
; The above map may help in reading.
; The neat arrangement of ports means that the B register need only be
; rotated left to work up the left hand side and then down the right
; hand side of the keyboard. When the reset bit drops into the carry
; then all 8 half-rows have been read. Shift is the first key to be
; read. The lower six bits of the shifts are unambiguous.
; -------------------------------
; THE 'KEYBOARD SCANNING' ROUTINE
; -------------------------------
; from keyboard and s-inkey$
; returns 1 or 2 keys in DE, most significant shift first if any
; key values 0-39 else 255
;; KEY-SCAN
L028E: LD L,$2F ; initial key value
; valid values are obtained by subtracting
; eight five times.
LD DE,$FFFF ; a buffer to receive 2 keys.
LD BC,$FEFE ; the commencing port address
; B holds 11111110 initially and is also
; used to count the 8 half-rows
;; KEY-LINE
L0296: IN A,(C) ; read the port to A - bits will be reset
; if a key is pressed else set.
CPL ; complement - pressed key-bits are now set
AND $1F ; apply 00011111 mask to pick up the
; relevant set bits.
JR Z,L02AB ; forward to KEY-DONE if zero and therefore
; no keys pressed in row at all.
LD H,A ; transfer row bits to H
LD A,L ; load the initial key value to A
;; KEY-3KEYS
L029F: INC D ; now test the key buffer
RET NZ ; if we have collected 2 keys already
; then too many so quit.
;; KEY-BITS
L02A1: SUB $08 ; subtract 8 from the key value
; cycling through key values (top = $27)
; e.g. 2F> 27>1F>17>0F>07
; 2E> 26>1E>16>0E>06
SRL H ; shift key bits right into carry.
JR NC,L02A1 ; back to KEY-BITS if not pressed
; but if pressed we have a value (0-39d)
LD D,E ; transfer a possible previous key to D
LD E,A ; transfer the new key to E
JR NZ,L029F ; back to KEY-3KEYS if there were more
; set bits - H was not yet zero.
;; KEY-DONE
L02AB: DEC L ; cycles 2F>2E>2D>2C>2B>2A>29>28 for
; each half-row.
RLC B ; form next port address e.g. FEFE > FDFE
JR C,L0296 ; back to KEY-LINE if still more rows to do.
LD A,D ; now test if D is still FF ?
INC A ; if it is zero we have at most 1 key
; range now $01-$28 (1-40d)
RET Z ; return if one key or no key.
CP $28 ; is it capsshift (was $27) ?
RET Z ; return if so.
CP $19 ; is it symbol shift (was $18) ?
RET Z ; return also
LD A,E ; now test E
LD E,D ; but first switch
LD D,A ; the two keys.
CP $18 ; is it symbol shift ?
RET ; return (with zero set if it was).
; but with symbol shift now in D
; ------------------------------
; Scan keyboard and decode value
; ------------------------------
; from interrupt 50 times a second
;
;; KEYBOARD
L02BF: CALL L028E ; routine KEY-SCAN
RET NZ ; return if invalid combinations
; then decrease the counters within the two key-state maps
; as this could cause one to become free.
; if the keyboard has not been pressed during the last five interrupts
; then both sets will be free.
LD HL,$5C00 ; point to KSTATE-0
;; K-ST-LOOP
L02C6: BIT 7,(HL) ; is it free ? ($FF)
JR NZ,L02D1 ; forward to K-CH-SET if so
INC HL ; address 5-counter
DEC (HL) ; decrease counter
DEC HL ; step back
JR NZ,L02D1 ; forward to K-CH-SET if not at end of count
LD (HL),$FF ; else mark it free.
;; K-CH-SET
L02D1: LD A,L ; store low address byte.
LD HL,$5C04 ; point to KSTATE-4
; (ld l, $04)
CP L ; have 2 been done ?
JR NZ,L02C6 ; back to K-ST-LOOP to consider this 2nd set
; now the raw key (0-38) is converted to a main key (uppercase).
CALL L031E ; routine K-TEST to get main key in A
RET NC ; return if single shift
LD HL,$5C00 ; point to KSTATE-0
CP (HL) ; does it match ?
JR Z,L0310 ; forward to K-REPEAT if so
; if not consider the second key map.
EX DE,HL ; save kstate-0 in de
LD HL,$5C04 ; point to KSTATE-4
CP (HL) ; does it match ?
JR Z,L0310 ; forward to K-REPEAT if so
; having excluded a repeating key we can now consider a new key.
; the second set is always examined before the first.
BIT 7,(HL) ; is it free ?
JR NZ,L02F1 ; forward to K-NEW if so.
EX DE,HL ; bring back kstate-0
BIT 7,(HL) ; is it free ?
RET Z ; return if not.
; as we have a key but nowhere to put it yet.
; continue or jump to here if one of the buffers was free.
;; K-NEW
L02F1: LD E,A ; store key in E
LD (HL),A ; place in free location
INC HL ; advance to interrupt counter
LD (HL),$05 ; and initialize to 5
INC HL ; advance to delay
LD A,($5C09) ; pick up system variable REPDEL
LD (HL),A ; and insert that for first repeat delay.
INC HL ; advance to last location of state map.
LD C,(IY+$07) ; pick up MODE (3 bytes)
LD D,(IY+$01) ; pick up FLAGS (3 bytes)
PUSH HL ; save state map location
; Note. could now have used.
; ld l,$41; ld c,(hl); ld l,$3B; ld d,(hl).
; six and two threes of course.
CALL L0333 ; routine K-DECODE
POP HL ; restore map pointer
LD (HL),A ; put decoded key in last location of map.
;; K-END
L0308: LD ($5C08),A ; update LASTK system variable.
SET 5,(IY+$01) ; update FLAGS - signal new key.
RET ; done
; ---------------------------
; THE 'REPEAT KEY' SUBROUTINE
; ---------------------------
; A possible repeat has been identified. HL addresses the raw (main) key.
; The last location holds the decoded key (from the first context).
;; K-REPEAT
L0310: INC HL ; advance
LD (HL),$05 ; maintain interrupt counter at 5
INC HL ; advance
DEC (HL) ; decrease REPDEL value.
RET NZ ; return if not yet zero.
LD A,($5C0A) ; REPPER
LD (HL),A ; but for subsequent repeats REPPER will be used.
INC HL ; advance
;
LD A,(HL) ; pick up the key decoded possibly in another
; context.
JR L0308 ; back to K-END
; --------------
; Test key value
; --------------
; also called from s-inkey$
; begin by testing for a shift with no other.
;; K-TEST
L031E: LD B,D ; load most significant key to B
; will be $FF if not shift.
LD D,$00 ; and reset D to index into main table
LD A,E ; load least significant key from E
CP $27 ; is it higher than 39d i.e. FF
RET NC ; return with just a shift (in B now)
CP $18 ; is it symbol shift ?
JR NZ,L032C ; forward to K-MAIN if not
; but we could have just symbol shift and no other
BIT 7,B ; is other key $FF (ie not shift)
RET NZ ; return with solitary symbol shift
;; K-MAIN
L032C: LD HL,L0205 ; address: MAIN-KEYS
ADD HL,DE ; add offset 0-38
LD A,(HL) ; pick up main key value
SCF ; set carry flag
RET ; return (B has other key still)
; -----------------
; Keyboard decoding
; -----------------
; also called from s-inkey$
;; K-DECODE
L0333: LD A,E ; pick up the stored main key
CP $3A ; an arbitrary point between digits and letters
JR C,L0367 ; forward to K-DIGIT with digits, space, enter.
DEC C ; decrease MODE ( 0='KLC', 1='E', 2='G')
JP M,L034F ; to K-KLC-LET if was zero
JR Z,L0341 ; to K-E-LET if was 1 for extended letters.
; proceed with graphic codes.
; Note. should selectively drop return address if code > 'U' ($55).
; i.e. abort the KEYBOARD call.
; e.g. cp 'V'; jr c addit; pop af; ;;addit etc. (5 bytes of instruction).
; (s-inkey$ never gets into graphics mode.)
;; addit
ADD A,$4F ; add offset to augment 'A' to graphics A say.
RET ; return.
; Note. ( but [GRAPH] V gives RND, etc ).
; ---
; the jump was to here with extended mode with uppercase A-Z.
;; K-E-LET
L0341: LD HL,L022C-$41 ; base address of E-UNSHIFT L022c
; ( $01EB in standard ROM )
INC B ; test B is it empty i.e. not a shift
JR Z,L034A ; forward to K-LOOK-UP if neither shift
LD HL,L0246-$41 ; Address: $0205 L0246-$41 EXT-SHIFT base
;; K-LOOK-UP
L034A: LD D,$00 ; prepare to index
ADD HL,DE ; add the main key value
LD A,(HL) ; pick up other mode value
RET ; return
; ---
; the jump was here with mode = 0
;; K-KLC-LET
L034F: LD HL,L026A-$41 ; prepare base of sym-codes
BIT 0,B ; shift=$27 sym-shift=$18
JR Z,L034A ; back to K-LOOK-UP with symbol-shift
BIT 3,D ; test FLAGS is it 'K' mode (from OUT-CURS)
JR Z,L0364 ; skip to K-TOKENS if so
BIT 3,(IY+$30) ; test FLAGS2 - consider CAPS LOCK ?
RET NZ ; return if so with main code.
INC B ; is shift being pressed ?
; result zero if not
RET NZ ; return if shift pressed.
ADD A,$20 ; else convert the code to lower case.
RET ; return.
; ---
; the jump was here for tokens
;; K-TOKENS
L0364: ADD A,$A5 ; add offset to main code so that 'A'
; becomes 'NEW' etc.
RET ; return
; ---
; the jump was here with digits, space, enter and symbol shift (< $xx)
;; K-DIGIT
L0367: CP $30 ; is it '0' or higher ?
RET C ; return with space, enter and symbol-shift
DEC C ; test MODE (was 0='KLC', 1='E', 2='G')
JP M,L039D ; jump to K-KLC-DGT if was 0.
JR NZ,L0389 ; forward to K-GRA-DGT if mode was 2.
; continue with extended digits 0-9.
LD HL,L0284-$30 ; $0254 - base of E-DIGITS
BIT 5,B ; test - shift=$27 sym-shift=$18
JR Z,L034A ; to K-LOOK-UP if sym-shift
CP $38 ; is character '8' ?
JR NC,L0382 ; to K-8-&-9 if greater than '7'
SUB $20 ; reduce to ink range $10-$17
INC B ; shift ?
RET Z ; return if not.
ADD A,$08 ; add 8 to give paper range $18 - $1F
RET ; return
; ---
; 89
;; K-8-&-9
L0382: SUB $36 ; reduce to 02 and 03 bright codes
INC B ; test if shift pressed.
RET Z ; return if not.
ADD A,$FE ; subtract 2 setting carry
RET ; to give 0 and 1 flash codes.
; ---
; graphics mode with digits
;; K-GRA-DGT
L0389: LD HL,L0260-$30 ; $0230 base address of CTL-CODES
CP $39 ; is key '9' ?
JR Z,L034A ; back to K-LOOK-UP - changed to $0F, GRAPHICS.
CP $30 ; is key '0' ?
JR Z,L034A ; back to K-LOOK-UP - changed to $0C, delete.
; for keys '0' - '7' we assign a mosaic character depending on shift.
AND $07 ; convert character to number. 0 - 7.
ADD A,$80 ; add offset - they start at $80
INC B ; destructively test for shift
RET Z ; and return if not pressed.
XOR $0F ; toggle bits becomes range $88-$8F
RET ; return.
; ---
; now digits in 'KLC' mode
;; K-KLC-DGT
L039D: INC B ; return with digit codes if neither
RET Z ; shift key pressed.
BIT 5,B ; test for caps shift.
LD HL,L0260-$30 ; prepare base of table CTL-CODES.
JR NZ,L034A ; back to K-LOOK-UP if shift pressed.
; must have been symbol shift
SUB $10 ; for ASCII most will now be correct
; on a standard typewriter.
CP $22 ; but '@' is not - see below.
JR Z,L03B2 ; forward to to K-@-CHAR if so
CP $20 ; '_' is the other one that fails
RET NZ ; return if not.
LD A,$5F ; substitute ASCII '_'
RET ; return.
; ---
;; K-@-CHAR
L03B2: LD A,$40 ; substitute ASCII '@'
RET ; return.
; ------------------------------------------------------------------------
; The Spectrum Input character keys. One or two are abbreviated.
; From $00 Flash 0 to $FF COPY. The routine above has decoded all these.
; | 00 Fl0| 01 Fl1| 02 Br0| 03 Br1| 04 In0| 05 In1| 06 CAP| 07 EDT|
; | 08 LFT| 09 RIG| 0A DWN| 0B UP | 0C DEL| 0D ENT| 0E SYM| 0F GRA|
; | 10 Ik0| 11 Ik1| 12 Ik2| 13 Ik3| 14 Ik4| 15 Ik5| 16 Ik6| 17 Ik7|
; | 18 Pa0| 19 Pa1| 1A Pa2| 1B Pa3| 1C Pa4| 1D Pa5| 1E Pa6| 1F Pa7|
; | 20 SP | 21 ! | 22 " | 23 # | 24 $ | 25 % | 26 & | 27 ' |
; | 28 ( | 29 ) | 2A * | 2B + | 2C , | 2D - | 2E . | 2F / |
; | 30 0 | 31 1 | 32 2 | 33 3 | 34 4 | 35 5 | 36 6 | 37 7 |
; | 38 8 | 39 9 | 3A : | 3B ; | 3C < | 3D = | 3E > | 3F ? |
; | 40 @ | 41 A | 42 B | 43 C | 44 D | 45 E | 46 F | 47 G |
; | 48 H | 49 I | 4A J | 4B K | 4C L | 4D M | 4E N | 4F O |
; | 50 P | 51 Q | 52 R | 53 S | 54 T | 55 U | 56 V | 57 W |
; | 58 X | 59 Y | 5A Z | 5B [ | 5C \ | 5D ] | 5E ^ | 5F _ |
; | 60 ukp| 61 a | 62 b | 63 c | 64 d | 65 e | 66 f | 67 g |
; | 68 h | 69 i | 6A j | 6B k | 6C l | 6D m | 6E n | 6F o |
; | 70 p | 71 q | 72 r | 73 s | 74 t | 75 u | 76 v | 77 w |
; | 78 x | 79 y | 7A z | 7B { | 7C | | 7D } | 7E ~ | 7F (c)|
; | 80 128| 81 129| 82 130| 83 131| 84 132| 85 133| 86 134| 87 135|
; | 88 136| 89 137| 8A 138| 8B 139| 8C 140| 8D 141| 8E 142| 8F 143|
; | 90 [A]| 91 [B]| 92 [C]| 93 [D]| 94 [E]| 95 [F]| 96 [G]| 97 [H]|
; | 98 [I]| 99 [J]| 9A [K]| 9B [L]| 9C [M]| 9D [N]| 9E [O]| 9F [P]|
; | A0 [Q]| A1 [R]| A2 [S]| A3 [T]| A4 [U]| A5 RND| A6 IK$| A7 PI |
; | A8 FN | A9 PNT| AA SC$| AB ATT| AC AT | AD TAB| AE VL$| AF COD|
; | B0 VAL| B1 LEN| B2 SIN| B3 COS| B4 TAN| B5 ASN| B6 ACS| B7 ATN|
; | B8 LN | B9 EXP| BA INT| BB SQR| BC SGN| BD ABS| BE PEK| BF IN |
; | C0 USR| C1 ST$| C2 CH$| C3 NOT| C4 BIN| C5 OR | C6 AND| C7 <= |
; | C8 >= | C9 <> | CA LIN| CB THN| CC TO | CD STP| CE DEF| CF CAT|
; | D0 FMT| D1 MOV| D2 ERS| D3 OPN| D4 CLO| D5 MRG| D6 VFY| D7 BEP|
; | D8 CIR| D9 INK| DA PAP| DB FLA| DC BRI| DD INV| DE OVR| DF OUT|
; | E0 LPR| E1 LLI| E2 STP| E3 REA| E4 DAT| E5 RES| E6 NEW| E7 BDR|
; | E8 CON| E9 DIM| EA REM| EB FOR| EC GTO| ED GSB| EE INP| EF LOA|
; | F0 LIS| F1 LET| F2 PAU| F3 NXT| F4 POK| F5 PRI| F6 PLO| F7 RUN|
; | F8 SAV| F9 RAN| FA IF | FB CLS| FC DRW| FD CLR| FE RET| FF CPY|
; Note that for simplicity, Sinclair have located all the control codes
; below the space character.
; ASCII DEL, $7F, has been made a copyright symbol.
; Also $60, '`', not used in BASIC but used in other languages, has been
; allocated the local currency symbol for the relevant country -
; ukp in most Spectrums.
; ------------------------------------------------------------------------
;**********************************
;** Part 3. LOUDSPEAKER ROUTINES **
;**********************************
; Documented by Alvin Albrecht.
; ------------------------------
; Routine to control loudspeaker
; ------------------------------
; Outputs a square wave of given duration and frequency
; to the loudspeaker.
; Enter with: DE = #cycles - 1
; HL = tone period as described next
;
; The tone period is measured in T states and consists of
; three parts: a coarse part (H register), a medium part
; (bits 7..2 of L) and a fine part (bits 1..0 of L) which
; contribute to the waveform timing as follows:
;
; coarse medium fine
; duration of low = 118 + 1024*H + 16*(L>>2) + 4*(L&0x3)
; duration of hi = 118 + 1024*H + 16*(L>>2) + 4*(L&0x3)
; Tp = tone period = 236 + 2048*H + 32*(L>>2) + 8*(L&0x3)
; = 236 + 2048*H + 8*L = 236 + 8*HL
;
; As an example, to output five seconds of middle C (261.624 Hz):
; (a) Tone period = 1/261.624 = 3.822ms
; (b) Tone period in T-States = 3.822ms*fCPU = 13378
; where fCPU = clock frequency of the CPU = 3.5MHz
; (c) Find H and L for desired tone period:
; HL = (Tp - 236) / 8 = (13378 - 236) / 8 = 1643 = 0x066B
; (d) Tone duration in cycles = 5s/3.822ms = 1308 cycles
; DE = 1308 - 1 = 0x051B
;
; The resulting waveform has a duty ratio of exactly 50%.
;
;
;; BEEPER
L03B5: DI ; Disable Interrupts so they don't disturb timing
LD A,L ;
SRL L ;
SRL L ; L = medium part of tone period
CPL ;
AND $03 ; A = 3 - fine part of tone period
LD C,A ;
LD B,$00 ;
LD IX,L03D1 ; Address: BE-IX+3
ADD IX,BC ; IX holds address of entry into the loop
; the loop will contain 0-3 NOPs, implementing
; the fine part of the tone period.
LD A,($5C48) ; BORDCR
AND $38 ; bits 5..3 contain border colour
RRCA ; border colour bits moved to 2..0
RRCA ; to match border bits on port #FE
RRCA ;
OR $08 ; bit 3 set (tape output bit on port #FE)
; for loud sound output
;; BE-IX+3
L03D1: NOP ;(4) ; optionally executed NOPs for small
; adjustments to tone period
;; BE-IX+2
L03D2: NOP ;(4) ;
;; BE-IX+1
L03D3: NOP ;(4) ;
;; BE-IX+0
L03D4: INC B ;(4) ;
INC C ;(4) ;
;; BE-H&L-LP
L03D6: DEC C ;(4) ; timing loop for duration of
JR NZ,L03D6 ;(12/7); high or low pulse of waveform
LD C,$3F ;(7) ;
DEC B ;(4) ;
JP NZ,L03D6 ;(10) ; to BE-H&L-LP
XOR $10 ;(7) ; toggle output beep bit
OUT ($FE),A ;(11) ; output pulse
LD B,H ;(4) ; B = coarse part of tone period
LD C,A ;(4) ; save port #FE output byte
BIT 4,A ;(8) ; if new output bit is high, go
JR NZ,L03F2 ;(12/7); to BE-AGAIN
LD A,D ;(4) ; one cycle of waveform has completed
OR E ;(4) ; (low->low). if cycle countdown = 0
JR Z,L03F6 ;(12/7); go to BE-END
LD A,C ;(4) ; restore output byte for port #FE
LD C,L ;(4) ; C = medium part of tone period
DEC DE ;(6) ; decrement cycle count
JP (IX) ;(8) ; do another cycle
;; BE-AGAIN ; halfway through cycle
L03F2: LD C,L ;(4) ; C = medium part of tone period
INC C ;(4) ; adds 16 cycles to make duration of high = duration of low
JP (IX) ;(8) ; do high pulse of tone
;; BE-END
L03F6: EI ; Enable Interrupts
RET ;
; -------------------
; Handle BEEP command
; -------------------
; BASIC interface to BEEPER subroutine.
; Invoked in BASIC with:
; BEEP dur, pitch
; where dur = duration in seconds
; pitch = # of semitones above/below middle C
;
; Enter with: pitch on top of calculator stack
; duration next on calculator stack
;
;; beep
L03F8: RST 28H ;; FP-CALC
DB $31 ;;duplicate ; duplicate pitch
DB $27 ;;int ; convert to integer
DB $C0 ;;st-mem-0 ; store integer pitch to memory 0
DB $03 ;;subtract ; calculate fractional part of pitch = fp_pitch - int_pitch
DB $34 ;;stk-data ; push constant
DB $EC ;;Exponent: $7C, Bytes: 4 ; constant = 0.05762265
DB $6C,$98,$1F,$F5 ;;($6C,$98,$1F,$F5)
DB $04 ;;multiply ; compute:
DB $A1 ;;stk-one ; 1 + 0.05762265 * fraction_part(pitch)
DB $0F ;;addition
DB $38 ;;end-calc ; leave on calc stack
LD HL,$5C92 ; MEM-0: number stored here is in 16 bit integer format (pitch)
; 0, 0/FF (pos/neg), LSB, MSB, 0
; LSB/MSB is stored in two's complement
; In the following, the pitch is checked if it is in the range -128<=p<=127
LD A,(HL) ; First byte must be zero, otherwise
AND A ; error in integer conversion
JR NZ,L046C ; to REPORT-B
INC HL ;
LD C,(HL) ; C = pos/neg flag = 0/FF
INC HL ;
LD B,(HL) ; B = LSB, two's complement
LD A,B ;
RLA ;
SBC A,A ; A = 0/FF if B is pos/neg
CP C ; must be the same as C if the pitch is -128<=p<=127
JR NZ,L046C ; if no, error REPORT-B
INC HL ; if -128<=p<=127, MSB will be 0/FF if B is pos/neg
CP (HL) ; verify this
JR NZ,L046C ; if no, error REPORT-B
; now we know -128<=p<=127
LD A,B ; A = pitch + 60
ADD A,$3C ; if -60<=pitch<=67,
JP P,L0425 ; goto BE-i-OK
JP PO,L046C ; if pitch <= 67 goto REPORT-B
; lower bound of pitch set at -60
;; BE-I-OK ; here, -60<=pitch<=127
; and A=pitch+60 -> 0<=A<=187
L0425: LD B,$FA ; 6 octaves below middle C
;; BE-OCTAVE ; A=# semitones above 5 octaves below middle C
L0427: INC B ; increment octave
SUB $0C ; 12 semitones = one octave
JR NC,L0427 ; to BE-OCTAVE
ADD A,$0C ; A = # semitones above C (0-11)
PUSH BC ; B = octave displacement from middle C, 2's complement: -5<=B<=10
LD HL,L046E ; Address: semi-tone
CALL L3406 ; routine LOC-MEM
; HL = 5*A + $046E
CALL L33B4 ; routine STACK-NUM
; read FP value (freq) from semitone table (HL) and push onto calc stack
RST 28H ;; FP-CALC
DB $04 ;;multiply mult freq by 1 + 0.0576 * fraction_part(pitch) stacked earlier
;; thus taking into account fractional part of pitch.
;; the number 0.0576*frequency is the distance in Hz to the next
;; note (verify with the frequencies recorded in the semitone
;; table below) so that the fraction_part of the pitch does
;; indeed represent a fractional distance to the next note.
DB $38 ;;end-calc HL points to first byte of fp num on stack = middle frequency to generate
POP AF ; A = octave displacement from middle C, 2's complement: -5<=A<=10
ADD A,(HL) ; increase exponent by A (equivalent to multiplying by 2^A)
LD (HL),A ;
RST 28H ;; FP-CALC
DB $C0 ;;st-mem-0 ; store frequency in memory 0
DB $02 ;;delete ; remove from calc stack
DB $31 ;;duplicate ; duplicate duration (seconds)
DB $38 ;;end-calc
CALL L1E94 ; routine FIND-INT1 ; FP duration to A
CP $0B ; if dur > 10 seconds,
JR NC,L046C ; goto REPORT-B
;;; The following calculation finds the tone period for HL and the cycle count
;;; for DE expected in the BEEPER subroutine. From the example in the BEEPER comments,
;;;
;;; HL = ((fCPU / f) - 236) / 8 = fCPU/8/f - 236/8 = 437500/f -29.5
;;; DE = duration * frequency - 1
;;;
;;; Note the different constant (30.125) used in the calculation of HL
;;; below. This is probably an error.
RST 28H ;; FP-CALC
DB $E0 ;;get-mem-0 ; push frequency
DB $04 ;;multiply ; result1: #cycles = duration * frequency
DB $E0 ;;get-mem-0 ; push frequency
DB $34 ;;stk-data ; push constant
DB $80 ;;Exponent $93, Bytes: 3 ; constant = 437500
DB $43,$55,$9F,$80 ;;($55,$9F,$80,$00)
DB $01 ;;exchange ; frequency on top
DB $05 ;;division ; 437500 / frequency
DB $34 ;;stk-data ; push constant
DB $35 ;;Exponent: $85, Bytes: 1 ; constant = 30.125
DB $71 ;;($71,$00,$00,$00)
DB $03 ;;subtract ; result2: tone_period(HL) = 437500 / freq - 30.125
DB $38 ;;end-calc
CALL L1E99 ; routine FIND-INT2
PUSH BC ; BC = tone_period(HL)
CALL L1E99 ; routine FIND-INT2, BC = #cycles to generate
POP HL ; HL = tone period
LD D,B ;
LD E,C ; DE = #cycles
LD A,D ;
OR E ;
RET Z ; if duration = 0, skip BEEP and avoid 65536 cycle
; boondoggle that would occur next
DEC DE ; DE = #cycles - 1
JP L03B5 ; to BEEPER
; ---
;; REPORT-B
L046C: RST 08H ; ERROR-1
DB $0A ; Error Report: Integer out of range
; ---------------
; Semi-tone table
; ---------------
;
; Holds frequencies corresponding to semitones in middle octave.
; To move n octaves higher or lower, frequencies are multiplied by 2^n.
;; semi-tone five byte fp decimal freq note (middle)
L046E: DB $89, $02, $D0, $12, $86; 261.625565290 C
DB $89, $0A, $97, $60, $75; 277.182631135 C#
DB $89, $12, $D5, $17, $1F; 293.664768100 D
DB $89, $1B, $90, $41, $02; 311.126983881 D#
DB $89, $24, $D0, $53, $CA; 329.627557039 E
DB $89, $2E, $9D, $36, $B1; 349.228231549 F
DB $89, $38, $FF, $49, $3E; 369.994422674 F#
DB $89, $43, $FF, $6A, $73; 391.995436072 G
DB $89, $4F, $A7, $00, $54; 415.304697513 G#
DB $89, $5C, $00, $00, $00; 440.000000000 A
DB $89, $69, $14, $F6, $24; 466.163761616 A#
DB $89, $76, $F1, $10, $05; 493.883301378 B
;****************************************
;** Part 4. CASSETTE HANDLING ROUTINES **
;****************************************
; These routines begin with the service routines followed by a single
; command entry point.
; The first of these service routines is a curiosity.
; -----------------------
; THE 'ZX81 NAME' ROUTINE
; -----------------------
; This routine fetches a filename in ZX81 format and is not used by the
; cassette handling routines in this ROM.
;; zx81-name
L04AA: CALL L24FB ; routine SCANNING to evaluate expression.
LD A,($5C3B) ; fetch system variable FLAGS.
ADD A,A ; test bit 7 - syntax, bit 6 - result type.
JP M,L1C8A ; to REPORT-C if not string result
; 'Nonsense in BASIC'.
POP HL ; drop return address.
RET NC ; return early if checking syntax.
PUSH HL ; re-save return address.
CALL L2BF1 ; routine STK-FETCH fetches string parameters.
LD H,D ; transfer start of filename
LD L,E ; to the HL register.
DEC C ; adjust to point to last character and
RET M ; return if the null string.
; or multiple of 256!
ADD HL,BC ; find last character of the filename.
; and also clear carry.
SET 7,(HL) ; invert it.
RET ; return.
; =========================================
;
; PORT 254 ($FE)
;
; spk mic { border }
; ___ ___ ___ ___ ___ ___ ___ ___
; PORT | | | | | | | | |
; 254 | | | | | | | | |
; $FE |___|___|___|___|___|___|___|___|
; 7 6 5 4 3 2 1 0
;
; ----------------------------------
; Save header and program/data bytes
; ----------------------------------
; This routine saves a section of data. It is called from SA-CTRL to save the
; seventeen bytes of header data. It is also the exit route from that routine
; when it is set up to save the actual data.
; On entry -
; HL points to start of data.
; IX points to descriptor.
; The accumulator is set to $00 for a header, $FF for data.
;; SA-BYTES
L04C2: LD HL,L053F ; address: SA/LD-RET
PUSH HL ; is pushed as common exit route.
; however there is only one non-terminal exit
; point.
LD HL,$1F80 ; a timing constant H=$1F, L=$80
; inner and outer loop counters
; a five second lead-in is used for a header.
BIT 7,A ; test one bit of accumulator.
; (AND A ?)
JR Z,L04D0 ; skip to SA-FLAG if a header is being saved.
; else is data bytes and a shorter lead-in is used.
LD HL,$0C98 ; another timing value H=$0C, L=$98.
; a two second lead-in is used for the data.
;; SA-FLAG
L04D0: EX AF,AF' ; save flag
INC DE ; increase length by one.
DEC IX ; decrease start.
DI ; disable interrupts
LD A,$02 ; select red for border, microphone bit on.
LD B,A ; also does as an initial slight counter value.
;; SA-LEADER
L04D8: DJNZ L04D8 ; self loop to SA-LEADER for delay.
; after initial loop, count is $A4 (or $A3)
OUT ($FE),A ; output byte $02/$0D to tape port.
XOR $0F ; switch from RED (mic on) to CYAN (mic off).
LD B,$A4 ; hold count. also timed instruction.
DEC L ; originally $80 or $98.
; but subsequently cycles 256 times.
JR NZ,L04D8 ; back to SA-LEADER until L is zero.
; the outer loop is counted by H
DEC B ; decrement count
DEC H ; originally twelve or thirty-one.
JP P,L04D8 ; back to SA-LEADER until H becomes $FF
; now send a synch pulse. At this stage mic is off and A holds value
; for mic on.
; A synch pulse is much shorter than the steady pulses of the lead-in.
LD B,$2F ; another short timed delay.
;; SA-SYNC-1
L04EA: DJNZ L04EA ; self loop to SA-SYNC-1
OUT ($FE),A ; switch to mic on and red.
LD A,$0D ; prepare mic off - cyan
LD B,$37 ; another short timed delay.
;; SA-SYNC-2
L04F2: DJNZ L04F2 ; self loop to SA-SYNC-2
OUT ($FE),A ; output mic off, cyan border.
LD BC,$3B0E ; B=$3B time(*), C=$0E, YELLOW, MIC OFF.
;
EX AF,AF' ; restore saved flag
; which is 1st byte to be saved.
LD L,A ; and transfer to L.
; the initial parity is A, $FF or $00.
JP L0507 ; JUMP forward to SA-START ->
; the mid entry point of loop.
; -------------------------
; During the save loop a parity byte is maintained in H.
; the save loop begins by testing if reduced length is zero and if so
; the final parity byte is saved reducing count to $FFFF.
;; SA-LOOP
L04FE: LD A,D ; fetch high byte
OR E ; test against low byte.
JR Z,L050E ; forward to SA-PARITY if zero.
LD L,(IX+$00) ; load currently addressed byte to L.
;; SA-LOOP-P
L0505: LD A,H ; fetch parity byte.
XOR L ; exclusive or with new byte.
; -> the mid entry point of loop.
;; SA-START
L0507: LD H,A ; put parity byte in H.
LD A,$01 ; prepare blue, mic=on.
SCF ; set carry flag ready to rotate in.
JP L0525 ; JUMP forward to SA-8-BITS -8->
; ---
;; SA-PARITY
L050E: LD L,H ; transfer the running parity byte to L and
JR L0505 ; back to SA-LOOP-P
; to output that byte before quitting normally.
; ---
; entry point to save yellow part of bit.
; a bit consists of a period with mic on and blue border followed by
; a period of mic off with yellow border.
; Note. since the DJNZ instruction does not affect flags, the zero flag is used
; to indicate which of the two passes is in effect and the carry maintains the
; state of the bit to be saved.
;; SA-BIT-2
L0511: LD A,C ; fetch 'mic on and yellow' which is
; held permanently in C.
BIT 7,B ; set the zero flag. B holds $3E.
; entry point to save 1 entire bit. For first bit B holds $3B(*).
; Carry is set if saved bit is 1. zero is reset NZ on entry.
;; SA-BIT-1
L0514: DJNZ L0514 ; self loop for delay to SA-BIT-1
JR NC,L051C ; forward to SA-OUT if bit is 0.
; but if bit is 1 then the mic state is held for longer.
LD B,$42 ; set timed delay. (66 decimal)
;; SA-SET
L051A: DJNZ L051A ; self loop to SA-SET
; (roughly an extra 66*13 clock cycles)
;; SA-OUT
L051C: OUT ($FE),A ; blue and mic on OR yellow and mic off.
LD B,$3E ; set up delay
JR NZ,L0511 ; back to SA-BIT-2 if zero reset NZ (first pass)
; proceed when the blue and yellow bands have been output.
DEC B ; change value $3E to $3D.
XOR A ; clear carry flag (ready to rotate in).
INC A ; reset zero flag ie. NZ.
; -8->
;; SA-8-BITS
L0525: RL L ; rotate left through carry
; C<76543210<C
JP NZ,L0514 ; JUMP back to SA-BIT-1
; until all 8 bits done.
; when the initial set carry is passed out again then a byte is complete.
DEC DE ; decrease length
INC IX ; increase byte pointer
LD B,$31 ; set up timing.
LD A,$7F ; test the space key and
IN A,($FE) ; return to common exit (to restore border)
RRA ; if a space is pressed
RET NC ; return to SA/LD-RET. - - >
; now test if byte counter has reached $FFFF.
LD A,D ; fetch high byte
INC A ; increment.
JP NZ,L04FE ; JUMP to SA-LOOP if more bytes.
LD B,$3B ; a final delay.
;; SA-DELAY
L053C: DJNZ L053C ; self loop to SA-DELAY
RET ; return - - >
; --------------------------------------------------
; Reset border and check BREAK key for LOAD and SAVE
; --------------------------------------------------
; the address of this routine is pushed on the stack prior to any load/save
; operation and it handles normal completion with the restoration of the
; border and also abnormal termination when the break key, or to be more
; precise the space key is pressed during a tape operation.
; - - >
;; SA/LD-RET
L053F: PUSH AF ; preserve accumulator throughout.
LD A,($5C48) ; fetch border colour from BORDCR.
AND $38 ; mask off paper bits.
RRCA ; rotate
RRCA ; to the
RRCA ; range 0-7.
;===============================
IF TAP_EMU_BORDER=1
DB 0,0
ELSE
OUT ($FE),A ; change the border colour.
ENDIF
;===============================
LD A,$7F ; read from port address $7FFE the
IN A,($FE) ; row with the space key at outside.
RRA ; test for space key pressed.
EI ; enable interrupts
JR C,L0554 ; forward to SA/LD-END if not
;; REPORT-Da
L0552: RST 08H ; ERROR-1
DB $0C ; Error Report: BREAK - CONT repeats
; ---
;; SA/LD-END
L0554: POP AF ; restore the accumulator.
RET ; return.
; ------------------------------------
; Load header or block of information
; ------------------------------------
; This routine is used to load bytes and on entry A is set to $00 for a
; header or to $FF for data. IX points to the start of receiving location
; and DE holds the length of bytes to be loaded. If, on entry the carry flag
; is set then data is loaded, if reset then it is verified.
;; LD-BYTES
L0556: INC D ; reset the zero flag without disturbing carry.
EX AF,AF' ; preserve entry flags.
DEC D ; restore high byte of length.
DI ; disable interrupts
LD A,$0F ; make the border white and mic off.
;===============================
IF TAP_EMU_BORDER=1
DB 0,0
ELSE
OUT ($FE),A ; output to port.
ENDIF
;===============================
LD HL,L053F ; Address: SA/LD-RET
PUSH HL ; is saved on stack as terminating routine.
; the reading of the EAR bit (D6) will always be preceded by a test of the
; space key (D0), so store the initial post-test state.
IN A,($FE) ; read the ear state - bit 6.
RRA ; rotate to bit 5.
AND $20 ; isolate this bit.
OR $02 ; combine with red border colour.
;===============================
RST 8
DB _TAPE_EMUL
; LD C,A ; and store initial state long-term in C.
; CP A ; set the zero flag.
;===============================
;; LD-BREAK
L056B: RET NZ ; return if at any time space is pressed.
;; LD-START
L056C: CALL L05E7 ; routine LD-EDGE-1
JR NC,L056B ; back to LD-BREAK with time out and no
; edge present on tape.
; but continue when a transition is found on tape.
LD HL,$0415 ; set up 16-bit outer loop counter for
; approx 1 second delay.
;; LD-WAIT
L0574: DJNZ L0574 ; self loop to LD-WAIT (for 256 times)
DEC HL ; decrease outer loop counter.
LD A,H ; test for
OR L ; zero.
JR NZ,L0574 ; back to LD-WAIT, if not zero, with zero in B.
; continue after delay with H holding zero and B also.
; sample 256 edges to check that we are in the middle of a lead-in section.
CALL L05E3 ; routine LD-EDGE-2
JR NC,L056B ; back to LD-BREAK
; if no edges at all.
;; LD-LEADER
L0580: LD B,$9C ; set timing value.
CALL L05E3 ; routine LD-EDGE-2
JR NC,L056B ; back to LD-BREAK if time-out
LD A,$C6 ; two edges must be spaced apart.
CP B ; compare
JR NC,L056C ; back to LD-START if too close together for a
; lead-in.
INC H ; proceed to test 256 edged sample.
JR NZ,L0580 ; back to LD-LEADER while more to do.
; sample indicates we are in the middle of a two or five second lead-in.
; Now test every edge looking for the terminal synch signal.
;; LD-SYNC
L058F: LD B,$C9 ; initial timing value in B.
CALL L05E7 ; routine LD-EDGE-1
JR NC,L056B ; back to LD-BREAK with time-out.
LD A,B ; fetch augmented timing value from B.
CP $D4 ; compare
JR NC,L058F ; back to LD-SYNC if gap too big, that is,
; a normal lead-in edge gap.
; but a short gap will be the synch pulse.
; in which case another edge should appear before B rises to $FF
CALL L05E7 ; routine LD-EDGE-1
RET NC ; return with time-out.
; proceed when the synch at the end of the lead-in is found.
; We are about to load data so change the border colours.
LD A,C ; fetch long-term mask from C
XOR $03 ; and make blue/yellow.
LD C,A ; store the new long-term byte.
LD H,$00 ; set up parity byte as zero.
LD B,$B0 ; timing.
JR L05C8 ; forward to LD-MARKER
; the loop mid entry point with the alternate
; zero flag reset to indicate first byte
; is discarded.
; --------------
; the loading loop loads each byte and is entered at the mid point.
;; LD-LOOP
L05A9: EX AF,AF' ; restore entry flags and type in A.
JR NZ,L05B3 ; forward to LD-FLAG if awaiting initial flag
; which is to be discarded.
JR NC,L05BD ; forward to LD-VERIFY if not to be loaded.
LD (IX+$00),L ; place loaded byte at memory location.
JR L05C2 ; forward to LD-NEXT
; ---
;; LD-FLAG
L05B3: RL C ; preserve carry (verify) flag in long-term
; state byte. Bit 7 can be lost.
XOR L ; compare type in A with first byte in L.
RET NZ ; return if no match e.g. CODE vs DATA.
; continue when data type matches.
LD A,C ; fetch byte with stored carry
RRA ; rotate it to carry flag again
LD C,A ; restore long-term port state.
INC DE ; increment length ??
JR L05C4 ; forward to LD-DEC.
; but why not to location after ?
; ---
; for verification the byte read from tape is compared with that in memory.
;; LD-VERIFY
L05BD: LD A,(IX+$00) ; fetch byte from memory.
XOR L ; compare with that on tape
RET NZ ; return if not zero.
;; LD-NEXT
L05C2: INC IX ; increment byte pointer.
;; LD-DEC
L05C4: DEC DE ; decrement length.
EX AF,AF' ; store the flags.
LD B,$B2 ; timing.
; when starting to read 8 bits the receiving byte is marked with bit at right.
; when this is rotated out again then 8 bits have been read.
;; LD-MARKER
L05C8: LD L,$01 ; initialize as %00000001
;; LD-8-BITS
L05CA: CALL L05E3 ; routine LD-EDGE-2 increments B relative to
; gap between 2 edges.
RET NC ; return with time-out.
LD A,$CB ; the comparison byte.
CP B ; compare to incremented value of B.
; if B is higher then bit on tape was set.
; if <= then bit on tape is reset.
RL L ; rotate the carry bit into L.
LD B,$B0 ; reset the B timer byte.
JP NC,L05CA ; JUMP back to LD-8-BITS
; when carry set then marker bit has been passed out and byte is complete.
LD A,H ; fetch the running parity byte.
XOR L ; include the new byte.
LD H,A ; and store back in parity register.
LD A,D ; check length of
OR E ; expected bytes.
JR NZ,L05A9 ; back to LD-LOOP
; while there are more.
; when all bytes loaded then parity byte should be zero.
LD A,H ; fetch parity byte.
CP $01 ; set carry if zero.
RET ; return
; in no carry then error as checksum disagrees.
; -------------------------
; Check signal being loaded
; -------------------------
; An edge is a transition from one mic state to another.
; More specifically a change in bit 6 of value input from port $FE.
; Graphically it is a change of border colour, say, blue to yellow.
; The first entry point looks for two adjacent edges. The second entry point
; is used to find a single edge.
; The B register holds a count, up to 256, within which the edge (or edges)
; must be found. The gap between two edges will be more for a '1' than a '0'
; so the value of B denotes the state of the bit (two edges) read from tape.
; ->
;; LD-EDGE-2
L05E3: CALL L05E7 ; call routine LD-EDGE-1 below.
RET NC ; return if space pressed or time-out.
; else continue and look for another adjacent
; edge which together represent a bit on the
; tape.
; ->
; this entry point is used to find a single edge from above but also
; when detecting a read-in signal on the tape.
;; LD-EDGE-1
L05E7: LD A,$16 ; a delay value of twenty two.
;; LD-DELAY
L05E9: DEC A ; decrement counter
JR NZ,L05E9 ; loop back to LD-DELAY 22 times.
AND A ; clear carry.
;; LD-SAMPLE
L05ED: INC B ; increment the time-out counter.
RET Z ; return with failure when $FF passed.
LD A,$7F ; prepare to read keyboard and EAR port
IN A,($FE) ; row $7FFE. bit 6 is EAR, bit 0 is SPACE key.
RRA ; test outer key the space. (bit 6 moves to 5)
RET NC ; return if space pressed. >>>
XOR C ; compare with initial long-term state.
AND $20 ; isolate bit 5
JR Z,L05ED ; back to LD-SAMPLE if no edge.
; but an edge, a transition of the EAR bit, has been found so switch the
; long-term comparison byte containing both border colour and EAR bit.
LD A,C ; fetch comparison value.
CPL ; switch the bits
LD C,A ; and put back in C for long-term.
AND $07 ; isolate new colour bits.
OR $08 ; set bit 3 - MIC off.
OUT ($FE),A ; send to port to effect change of colour.
SCF ; set carry flag signaling edge found within
; time allowed.
RET ; return.
; ---------------------------------
; Entry point for all tape commands
; ---------------------------------
; This is the single entry point for the four tape commands.
; The routine first determines in what context it has been called by examining
; the low byte of the Syntax table entry which was stored in T_ADDR.
; Subtracting $EO (the present arrangement) gives a value of
; $00 - SAVE
; $01 - LOAD
; $02 - VERIFY
; $03 - MERGE
; As with all commands the address STMT-RET is on the stack.
;; SAVE-ETC
L0605: POP AF ; discard address STMT-RET.
LD A,($5C74) ; fetch T_ADDR
; Now reduce the low byte of the Syntax table entry to give command.
; Note. For ZASM use SUB $E0 as next instruction.
L0609 SUB LOW (L1ADF)+1 ; subtract the known offset.
; ( is SUB $E0 in standard ROM )
LD ($5C74),A ; and put back in T_ADDR as 0,1,2, or 3
; for future reference.
CALL L1C8C ; routine EXPT-EXP checks that a string
; expression follows and stacks the
; parameters in run-time.
CALL L2530 ; routine SYNTAX-Z
JR Z,L0652 ; forward to SA-DATA if checking syntax.
LD BC,$0011 ; presume seventeen bytes for a header.
LD A,($5C74) ; fetch command from T_ADDR.
AND A ; test for zero - SAVE.
JR Z,L0621 ; forward to SA-SPACE if so.
LD C,$22 ; else double length to thirty four.
;; SA-SPACE
L0621: RST 30H ; BC-SPACES creates 17/34 bytes in workspace.
PUSH DE ; transfer the start of new space to
POP IX ; the available index register.
; ten spaces are required for the default filename but it is simpler to
; overwrite the first file-type indicator byte as well.
LD B,$0B ; set counter to eleven.
LD A,$20 ; prepare a space.
;; SA-BLANK
L0629: LD (DE),A ; set workspace location to space.
INC DE ; next location.
DJNZ L0629 ; loop back to SA-BLANK till all eleven done.
LD (IX+$01),$FF ; set first byte of ten character filename
; to $FF as a default to signal null string.
CALL L2BF1 ; routine STK-FETCH fetches the filename
; parameters from the calculator stack.
; length of string in BC.
; start of string in DE.
LD HL,$FFF6 ; prepare the value minus ten.
DEC BC ; decrement length.
; ten becomes nine, zero becomes $FFFF.
ADD HL,BC ; trial addition.
INC BC ; restore true length.
JR NC,L064B ; forward to SA-NAME if length is one to ten.
; the filename is more than ten characters in length or the null string.
LD A,($5C74) ; fetch command from T_ADDR.
AND A ; test for zero - SAVE.
JR NZ,L0644 ; forward to SA-NULL if not the SAVE command.
; but no more than ten characters are allowed for SAVE.
; The first ten characters of any other command parameter are acceptable.
; Weird, but necessary, if saving to sectors.
; Note. the golden rule that there are no restriction on anything is broken.
;; REPORT-Fa
L0642: RST 08H ; ERROR-1
DB $0E ; Error Report: Invalid file name
; continue with LOAD, MERGE, VERIFY and also SAVE within ten character limit.
;; SA-NULL
L0644: LD A,B ; test length of filename
OR C ; for zero.
JR Z,L0652 ; forward to SA-DATA if so using the 255
; indicator followed by spaces.
LD BC,$000A ; else trim length to ten.
; other paths rejoin here with BC holding length in range 1 - 10.
;; SA-NAME
L064B: PUSH IX ; push start of file descriptor.
POP HL ; and pop into HL.
INC HL ; HL now addresses first byte of filename.
EX DE,HL ; transfer destination address to DE, start
; of string in command to HL.
LDIR ; copy up to ten bytes
; if less than ten then trailing spaces follow.
; the case for the null string rejoins here.
;; SA-DATA
L0652: RST 18H ; GET-CHAR
CP $E4 ; is character after filename the token 'DATA' ?
JR NZ,L06A0 ; forward to SA-SCR$ to consider SCREEN$ if
; not.
; continue to consider DATA.
LD A,($5C74) ; fetch command from T_ADDR
CP $03 ; is it 'VERIFY' ?
JP Z,L1C8A ; jump forward to REPORT-C if so.
; 'Nonsense in BASIC'
; VERIFY "d" DATA is not allowed.
; continue with SAVE, LOAD, MERGE of DATA.
RST 20H ; NEXT-CHAR
CALL L28B2 ; routine LOOK-VARS searches variables area
; returning with carry reset if found or
; checking syntax.
SET 7,C ; this converts a simple string to a
; string array. The test for an array or string
; comes later.
JR NC,L0672 ; forward to SA-V-OLD if variable found.
LD HL,$0000 ; set destination to zero as not fixed.
LD A,($5C74) ; fetch command from T_ADDR
DEC A ; test for 1 - LOAD
JR Z,L0685 ; forward to SA-V-NEW with LOAD DATA.
; to load a new array.
; otherwise the variable was not found in run-time with SAVE/MERGE.
;; REPORT-2a
L0670: RST 08H ; ERROR-1
DB $01 ; Error Report: Variable not found
; continue with SAVE/LOAD DATA
;; SA-V-OLD
L0672: JP NZ,L1C8A ; to REPORT-C if not an array variable.
; or erroneously a simple string.
; 'Nonsense in BASIC'
CALL L2530 ; routine SYNTAX-Z
JR Z,L0692 ; forward to SA-DATA-1 if checking syntax.
INC HL ; step past single character variable name.
LD A,(HL) ; fetch low byte of length.
LD (IX+$0B),A ; place in descriptor.
INC HL ; point to high byte.
LD A,(HL) ; and transfer that
LD (IX+$0C),A ; to descriptor.
INC HL ; increase pointer within variable.
;; SA-V-NEW
L0685: LD (IX+$0E),C ; place character array name in header.
LD A,$01 ; default to type numeric.
BIT 6,C ; test result from look-vars.
JR Z,L068F ; forward to SA-V-TYPE if numeric.
INC A ; set type to 2 - string array.
;; SA-V-TYPE
L068F: LD (IX+$00),A ; place type 0, 1 or 2 in descriptor.
;; SA-DATA-1
L0692: EX DE,HL ; save var pointer in DE
RST 20H ; NEXT-CHAR
CP $29 ; is character ')' ?
JR NZ,L0672 ; back if not to SA-V-OLD to report
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR advances character address.
CALL L1BEE ; routine CHECK-END errors if not end of
; the statement.
EX DE,HL ; bring back variables data pointer.
JP L075A ; jump forward to SA-ALL
; ---
; the branch was here to consider a 'SCREEN$', the display file.
;; SA-SCR$
L06A0: CP $AA ; is character the token 'SCREEN$' ?
JR NZ,L06C3 ; forward to SA-CODE if not.
LD A,($5C74) ; fetch command from T_ADDR
CP $03 ; is it MERGE ?
JP Z,L1C8A ; jump to REPORT-C if so.
; 'Nonsense in BASIC'
; continue with SAVE/LOAD/VERIFY SCREEN$.
RST 20H ; NEXT-CHAR
CALL L1BEE ; routine CHECK-END errors if not at end of
; statement.
; continue in runtime.
LD (IX+$0B),$00 ; set descriptor length
LD (IX+$0C),$1B ; to $1b00 to include bitmaps and attributes.
LD HL,$4000 ; set start to display file start.
LD (IX+$0D),L ; place start in
LD (IX+$0E),H ; the descriptor.
JR L0710 ; forward to SA-TYPE-3
; ---
; the branch was here to consider CODE.
;; SA-CODE
L06C3: CP $AF ; is character the token 'CODE' ?
JR NZ,L0716 ; forward if not to SA-LINE to consider an
; auto-started BASIC program.
LD A,($5C74) ; fetch command from T_ADDR
CP $03 ; is it MERGE ?
JP Z,L1C8A ; jump forward to REPORT-C if so.
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR advances character address.
CALL L2048 ; routine PR-ST-END checks if a carriage
; return or ':' follows.
JR NZ,L06E1 ; forward to SA-CODE-1 if there are parameters.
LD A,($5C74) ; else fetch the command from T_ADDR.
AND A ; test for zero - SAVE without a specification.
JP Z,L1C8A ; jump to REPORT-C if so.
; 'Nonsense in BASIC'
; for LOAD/VERIFY put zero on stack to signify handle at location saved from.
CALL L1CE6 ; routine USE-ZERO
JR L06F0 ; forward to SA-CODE-2
; ---
; if there are more characters after CODE expect start and possibly length.
;; SA-CODE-1
L06E1: CALL L1C82 ; routine EXPT-1NUM checks for numeric
; expression and stacks it in run-time.
RST 18H ; GET-CHAR
CP $2C ; does a comma follow ?
JR Z,L06F5 ; forward if so to SA-CODE-3
; else allow saved code to be loaded to a specified address.
LD A,($5C74) ; fetch command from T_ADDR.
AND A ; is the command SAVE which requires length ?
JP Z,L1C8A ; jump to REPORT-C if so.
; 'Nonsense in BASIC'
; the command LOAD code may rejoin here with zero stacked as start.
;; SA-CODE-2
L06F0: CALL L1CE6 ; routine USE-ZERO stacks zero for length.
JR L06F9 ; forward to SA-CODE-4
; ---
; the branch was here with SAVE CODE start,
;; SA-CODE-3
L06F5: RST 20H ; NEXT-CHAR advances character address.
CALL L1C82 ; routine EXPT-1NUM checks for expression
; and stacks in run-time.
; paths converge here and nothing must follow.
;; SA-CODE-4
L06F9: CALL L1BEE ; routine CHECK-END errors with extraneous
; characters and quits if checking syntax.
; in run-time there are two 16-bit parameters on the calculator stack.
CALL L1E99 ; routine FIND-INT2 gets length.
LD (IX+$0B),C ; place length
LD (IX+$0C),B ; in descriptor.
CALL L1E99 ; routine FIND-INT2 gets start.
LD (IX+$0D),C ; place start
LD (IX+$0E),B ; in descriptor.
LD H,B ; transfer the
LD L,C ; start to HL also.
;; SA-TYPE-3
L0710: LD (IX+$00),$03 ; place type 3 - code in descriptor.
JR L075A ; forward to SA-ALL.
; ---
; the branch was here with BASIC to consider an optional auto-start line
; number.
;; SA-LINE
L0716: CP $CA ; is character the token 'LINE' ?
JR Z,L0723 ; forward to SA-LINE-1 if so.
; else all possibilities have been considered and nothing must follow.
CALL L1BEE ; routine CHECK-END
; continue in run-time to save BASIC without auto-start.
LD (IX+$0E),$80 ; place high line number in descriptor to
; disable auto-start.
JR L073A ; forward to SA-TYPE-0 to save program.
; ---
; the branch was here to consider auto-start.
;; SA-LINE-1
L0723: LD A,($5C74) ; fetch command from T_ADDR
AND A ; test for SAVE.
JP NZ,L1C8A ; jump forward to REPORT-C with anything else.
; 'Nonsense in BASIC'
;
RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM checks for numeric
; expression and stacks in run-time.
CALL L1BEE ; routine CHECK-END quits if syntax path.
CALL L1E99 ; routine FIND-INT2 fetches the numeric
; expression.
LD (IX+$0D),C ; place the auto-start
LD (IX+$0E),B ; line number in the descriptor.
; Note. this isn't checked, but is subsequently handled by the system.
; If the user typed 40000 instead of 4000 then it won't auto-start
; at line 4000, or indeed, at all.
; continue to save program and any variables.
;; SA-TYPE-0
L073A: LD (IX+$00),$00 ; place type zero - program in descriptor.
LD HL,($5C59) ; fetch E_LINE to HL.
LD DE,($5C53) ; fetch PROG to DE.
SCF ; set carry flag to calculate from end of
; variables E_LINE -1.
SBC HL,DE ; subtract to give total length.
LD (IX+$0B),L ; place total length
LD (IX+$0C),H ; in descriptor.
LD HL,($5C4B) ; load HL from system variable VARS
SBC HL,DE ; subtract to give program length.
LD (IX+$0F),L ; place length of program
LD (IX+$10),H ; in the descriptor.
EX DE,HL ; start to HL, length to DE.
;; SA-ALL
L075A: LD A,($5C74) ; fetch command from T_ADDR
AND A ; test for zero - SAVE.
JP Z,L0970 ; jump forward to SA-CONTRL with SAVE ->
; ---
; continue with LOAD, MERGE and VERIFY.
PUSH HL ; save start.
LD BC,$0011 ; prepare to add seventeen
ADD IX,BC ; to point IX at second descriptor.
;; LD-LOOK-H
L0767: PUSH IX ; save IX
LD DE,$0011 ; seventeen bytes
XOR A ; reset zero flag
SCF ; set carry flag
CALL L0556 ; routine LD-BYTES loads a header from tape
; to second descriptor.
POP IX ; restore IX.
JR NC,L0767 ; loop back to LD-LOOK-H until header found.
LD A,$FE ; select system channel 'S'
CALL L1601 ; routine CHAN-OPEN opens it.
LD (IY+$52),$03 ; set SCR_CT to 3 lines.
LD C,$80 ; C has bit 7 set to indicate type mismatch as
; a default startpoint.
LD A,(IX+$00) ; fetch loaded header type to A
CP (IX-$11) ; compare with expected type.
JR NZ,L078A ; forward to LD-TYPE with mis-match.
LD C,$F6 ; set C to minus ten - will count characters
; up to zero.
;; LD-TYPE
L078A: CP $04 ; check if type in acceptable range 0 - 3.
JR NC,L0767 ; back to LD-LOOK-H with 4 and over.
; else A indicates type 0-3.
LD DE,L09C0 ; address base of last 4 tape messages
PUSH BC ; save BC
CALL L0C0A ; routine PO-MSG outputs relevant message.
; Note. all messages have a leading newline.
POP BC ; restore BC
PUSH IX ; transfer IX,
POP DE ; the 2nd descriptor, to DE.
LD HL,$FFF0 ; prepare minus seventeen.
ADD HL,DE ; add to point HL to 1st descriptor.
LD B,$0A ; the count will be ten characters for the
; filename.
LD A,(HL) ; fetch first character and test for
INC A ; value 255.
JR NZ,L07A6 ; forward to LD-NAME if not the wildcard.
; but if it is the wildcard, then add ten to C which is minus ten for a type
; match or -128 for a type mismatch. Although characters have to be counted
; bit 7 of C will not alter from state set here.
LD A,C ; transfer $F6 or $80 to A
ADD A,B ; add $0A
LD C,A ; place result, zero or -118, in C.
; At this point we have either a type mismatch, a wildcard match or ten
; characters to be counted. The characters must be shown on the screen.
;; LD-NAME
L07A6: INC DE ; address next input character
LD A,(DE) ; fetch character
CP (HL) ; compare to expected
INC HL ; address next expected character
JR NZ,L07AD ; forward to LD-CH-PR with mismatch
INC C ; increment matched character count
;; LD-CH-PR
L07AD: RST 10H ; PRINT-A prints character
DJNZ L07A6 ; loop back to LD-NAME for ten characters.
; if ten characters matched and the types previously matched then C will
; now hold zero.
BIT 7,C ; test if all matched
JR NZ,L0767 ; back to LD-LOOK-H if not
; else print a terminal carriage return.
LD A,$0D ; prepare carriage return.
RST 10H ; PRINT-A outputs it.
; The various control routines for LOAD, VERIFY and MERGE are executed
; during the one-second gap following the header on tape.
POP HL ; restore xx
LD A,(IX+$00) ; fetch incoming type
CP $03 ; compare with CODE
JR Z,L07CB ; forward to VR-CONTROL if it is CODE.
; type is a program or an array.
LD A,($5C74) ; fetch command from T_ADDR
DEC A ; was it LOAD ?
JP Z,L0808 ; JUMP forward to LD-CONTRL if so to
; load BASIC or variables.
CP $02 ; was command MERGE ?
JP Z,L08B6 ; jump forward to ME-CONTRL if so.
; else continue into VERIFY control routine to verify.
; ---------------------
; Handle VERIFY control
; ---------------------
; There are two branches to this routine.
; 1) From above to verify a program or array
; 2) from earlier with no carry to load or verify code.
;; VR-CONTROL
L07CB: PUSH HL ; save pointer to data.
LD L,(IX-$06) ; fetch length of old data
LD H,(IX-$05) ; to HL.
LD E,(IX+$0B) ; fetch length of new data
LD D,(IX+$0C) ; to DE.
LD A,H ; check length of old
OR L ; for zero.
JR Z,L07E9 ; forward to VR-CONT-1 if length unspecified
; e.g LOAD "x" CODE
; as opposed to, say, LOAD 'x' CODE 32768,300.
SBC HL,DE ; subtract the two lengths.
JR C,L0806 ; forward to REPORT-R if the length on tape is
; larger than that specified in command.
; 'Tape loading error'
JR Z,L07E9 ; forward to VR-CONT-1 if lengths match.
; a length on tape shorter than expected is not allowed for CODE
LD A,(IX+$00) ; else fetch type from tape.
CP $03 ; is it CODE ?
JR NZ,L0806 ; forward to REPORT-R if so
; 'Tape loading error'
;; VR-CONT-1
L07E9: POP HL ; pop pointer to data
LD A,H ; test for zero
OR L ; e.g. LOAD 'x' CODE
JR NZ,L07F4 ; forward to VR-CONT-2 if destination specified.
LD L,(IX+$0D) ; else use the destination in the header
LD H,(IX+$0E) ; and load code at address saved from.
;; VR-CONT-2
L07F4: PUSH HL ; push pointer to start of data block.
POP IX ; transfer to IX.
LD A,($5C74) ; fetch reduced command from T_ADDR
CP $02 ; is it VERIFY ?
SCF ; prepare a set carry flag
JR NZ,L0800 ; skip to VR-CONT-3 if not
AND A ; clear carry flag for VERIFY so that
; data is not loaded.
;; VR-CONT-3
L0800: LD A,$FF ; signal data block to be loaded
; -----------------
; Load a data block
; -----------------
; This routine is called from 3 places other than above to load a data block.
; In all cases the accumulator is first set to $FF so the routine could be
; called at the previous instruction.
;; LD-BLOCK
L0802: CALL L0556 ; routine LD-BYTES
RET C ; return if successful.
;; REPORT-R
L0806: RST 08H ; ERROR-1
DB $1A ; Error Report: Tape loading error
; -------------------
; Handle LOAD control
; -------------------
; This branch is taken when the command is LOAD with type 0, 1 or 2.
;; LD-CONTRL
L0808: LD E,(IX+$0B) ; fetch length of found data block
LD D,(IX+$0C) ; from 2nd descriptor.
PUSH HL ; save destination
LD A,H ; test for zero
OR L ;
JR NZ,L0819 ; forward if not to LD-CONT-1
INC DE ; increase length
INC DE ; for letter name
INC DE ; and 16-bit length
EX DE,HL ; length to HL,
JR L0825 ; forward to LD-CONT-2
; ---
;; LD-CONT-1
L0819: LD L,(IX-$06) ; fetch length from
LD H,(IX-$05) ; the first header.
EX DE,HL ;
SCF ; set carry flag
SBC HL,DE ;
JR C,L082E ; to LD-DATA
;; LD-CONT-2
L0825: LD DE,$0005 ; allow overhead of five bytes.
ADD HL,DE ; add in the difference in data lengths.
LD B,H ; transfer to
LD C,L ; the BC register pair
CALL L1F05 ; routine TEST-ROOM fails if not enough room.
;; LD-DATA
L082E: POP HL ; pop destination
LD A,(IX+$00) ; fetch type 0, 1 or 2.
AND A ; test for program and variables.
JR Z,L0873 ; forward if so to LD-PROG
; the type is a numeric or string array.
LD A,H ; test the destination for zero
OR L ; indicating variable does not already exist.
JR Z,L084C ; forward if so to LD-DATA-1
; else the destination is the first dimension within the array structure
DEC HL ; address high byte of total length
LD B,(HL) ; transfer to B.
DEC HL ; address low byte of total length.
LD C,(HL) ; transfer to C.
DEC HL ; point to letter of variable.
INC BC ; adjust length to
INC BC ; include these
INC BC ; three bytes also.
LD ($5C5F),IX ; save header pointer in X_PTR.
CALL L19E8 ; routine RECLAIM-2 reclaims the old variable
; sliding workspace including the two headers
; downwards.
LD IX,($5C5F) ; reload IX from X_PTR which will have been
; adjusted down by POINTERS routine.
;; LD-DATA-1
L084C: LD HL,($5C59) ; address E_LINE
DEC HL ; now point to the $80 variables end-marker.
LD C,(IX+$0B) ; fetch new data length
LD B,(IX+$0C) ; from 2nd header.
PUSH BC ; * save it.
INC BC ; adjust the
INC BC ; length to include
INC BC ; letter name and total length.
LD A,(IX-$03) ; fetch letter name from old header.
PUSH AF ; preserve accumulator though not corrupted.
CALL L1655 ; routine MAKE-ROOM creates space for variable
; sliding workspace up. IX no longer addresses
; anywhere meaningful.
INC HL ; point to first new location.
POP AF ; fetch back the letter name.
LD (HL),A ; place in first new location.
POP DE ; * pop the data length.
INC HL ; address 2nd location
LD (HL),E ; store low byte of length.
INC HL ; address next.
LD (HL),D ; store high byte.
INC HL ; address start of data.
PUSH HL ; transfer address
POP IX ; to IX register pair.
SCF ; set carry flag indicating load not verify.
LD A,$FF ; signal data not header.
JP L0802 ; JUMP back to LD-BLOCK
; -----------------
; the branch is here when a program as opposed to an array is to be loaded.
;; LD-PROG
L0873: EX DE,HL ; transfer dest to DE.
LD HL,($5C59) ; address E_LINE
DEC HL ; now variables end-marker.
LD ($5C5F),IX ; place the IX header pointer in X_PTR
LD C,(IX+$0B) ; get new length
LD B,(IX+$0C) ; from 2nd header
PUSH BC ; and save it.
CALL L19E5 ; routine RECLAIM-1 reclaims program and vars.
; adjusting X-PTR.
POP BC ; restore new length.
PUSH HL ; * save start
PUSH BC ; ** and length.
CALL L1655 ; routine MAKE-ROOM creates the space.
LD IX,($5C5F) ; reload IX from adjusted X_PTR
INC HL ; point to start of new area.
LD C,(IX+$0F) ; fetch length of BASIC on tape
LD B,(IX+$10) ; from 2nd descriptor
ADD HL,BC ; add to address the start of variables.
LD ($5C4B),HL ; set system variable VARS
LD H,(IX+$0E) ; fetch high byte of autostart line number.
LD A,H ; transfer to A
AND $C0 ; test if greater than $3F.
JR NZ,L08AD ; forward to LD-PROG-1 if so with no autostart.
LD L,(IX+$0D) ; else fetch the low byte.
LD ($5C42),HL ; set sytem variable to line number NEWPPC
LD (IY+$0A),$00 ; set statement NSPPC to zero.
;; LD-PROG-1
L08AD: POP DE ; ** pop the length
POP IX ; * and start.
SCF ; set carry flag
LD A,$FF ; signal data as opposed to a header.
JP L0802 ; jump back to LD-BLOCK
; --------------------
; Handle MERGE control
; --------------------
; the branch was here to merge a program and its variables or an array.
;
;; ME-CONTRL
L08B6: LD C,(IX+$0B) ; fetch length
LD B,(IX+$0C) ; of data block on tape.
PUSH BC ; save it.
INC BC ; one for the pot.
RST 30H ; BC-SPACES creates room in workspace.
; HL addresses last new location.
LD (HL),$80 ; place end-marker at end.
EX DE,HL ; transfer first location to HL.
POP DE ; restore length to DE.
PUSH HL ; save start.
PUSH HL ; and transfer it
POP IX ; to IX register.
SCF ; set carry flag to load data on tape.
LD A,$FF ; signal data not a header.
CALL L0802 ; routine LD-BLOCK loads to workspace.
POP HL ; restore first location in workspace to HL.
X08CE LD DE,($5C53) ; set DE from system variable PROG.
; now enter a loop to merge the data block in workspace with the program and
; variables.
;; ME-NEW-LP
L08D2: LD A,(HL) ; fetch next byte from workspace.
AND $C0 ; compare with $3F.
JR NZ,L08F0 ; forward to ME-VAR-LP if a variable or
; end-marker.
; continue when HL addresses a BASIC line number.
;; ME-OLD-LP
L08D7: LD A,(DE) ; fetch high byte from program area.
INC DE ; bump prog address.
CP (HL) ; compare with that in workspace.
INC HL ; bump workspace address.
JR NZ,L08DF ; forward to ME-OLD-L1 if high bytes don't match
LD A,(DE) ; fetch the low byte of program line number.
CP (HL) ; compare with that in workspace.
;; ME-OLD-L1
L08DF: DEC DE ; point to start of
DEC HL ; respective lines again.
JR NC,L08EB ; forward to ME-NEW-L2 if line number in
; workspace is less than or equal to current
; program line as has to be added to program.
PUSH HL ; else save workspace pointer.
EX DE,HL ; transfer prog pointer to HL
CALL L19B8 ; routine NEXT-ONE finds next line in DE.
POP HL ; restore workspace pointer
JR L08D7 ; back to ME-OLD-LP until destination position
; in program area found.
; ---
; the branch was here with an insertion or replacement point.
;; ME-NEW-L2
L08EB: CALL L092C ; routine ME-ENTER enters the line
JR L08D2 ; loop back to ME-NEW-LP.
; ---
; the branch was here when the location in workspace held a variable.
;; ME-VAR-LP
L08F0: LD A,(HL) ; fetch first byte of workspace variable.
LD C,A ; copy to C also.
CP $80 ; is it the end-marker ?
RET Z ; return if so as complete. >>>>>
PUSH HL ; save workspace area pointer.
LD HL,($5C4B) ; load HL with VARS - start of variables area.
;; ME-OLD-VP
L08F9: LD A,(HL) ; fetch first byte.
CP $80 ; is it the end-marker ?
JR Z,L0923 ; forward if so to ME-VAR-L2 to add
; variable at end of variables area.
CP C ; compare with variable in workspace area.
JR Z,L0909 ; forward to ME-OLD-V2 if a match to replace.
; else entire variables area has to be searched.
;; ME-OLD-V1
L0901: PUSH BC ; save character in C.
CALL L19B8 ; routine NEXT-ONE gets following variable
; address in DE.
POP BC ; restore character in C
EX DE,HL ; transfer next address to HL.
JR L08F9 ; loop back to ME-OLD-VP
; ---
; the branch was here when first characters of name matched.
;; ME-OLD-V2
L0909: AND $E0 ; keep bits 11100000
CP $A0 ; compare 10100000 - a long-named variable.
JR NZ,L0921 ; forward to ME-VAR-L1 if just one-character.
; but long-named variables have to be matched character by character.
POP DE ; fetch workspace 1st character pointer
PUSH DE ; and save it on the stack again.
PUSH HL ; save variables area pointer on stack.
;; ME-OLD-V3
L0912: INC HL ; address next character in vars area.
INC DE ; address next character in workspace area.
LD A,(DE) ; fetch workspace character.
CP (HL) ; compare to variables character.
JR NZ,L091E ; forward to ME-OLD-V4 with a mismatch.
RLA ; test if the terminal inverted character.
JR NC,L0912 ; loop back to ME-OLD-V3 if more to test.
; otherwise the long name matches in its entirety.
POP HL ; restore pointer to first character of variable
JR L0921 ; forward to ME-VAR-L1
; ---
; the branch is here when two characters don't match
;; ME-OLD-V4
L091E: POP HL ; restore the prog/vars pointer.
JR L0901 ; back to ME-OLD-V1 to resume search.
; ---
; branch here when variable is to replace an existing one
;; ME-VAR-L1
L0921: LD A,$FF ; indicate a replacement.
; this entry point is when A holds $80 indicating a new variable.
;; ME-VAR-L2
L0923: POP DE ; pop workspace pointer.
EX DE,HL ; now make HL workspace pointer, DE vars pointer
INC A ; zero flag set if replacement.
SCF ; set carry flag indicating a variable not a
; program line.
CALL L092C ; routine ME-ENTER copies variable in.
JR L08F0 ; loop back to ME-VAR-LP
; ------------------------
; Merge a Line or Variable
; ------------------------
; A BASIC line or variable is inserted at the current point. If the line numbers
; or variable names match (zero flag set) then a replacement takes place.
;; ME-ENTER
L092C: JR NZ,L093E ; forward to ME-ENT-1 for insertion only.
; but the program line or variable matches so old one is reclaimed.
EX AF,AF' ; save flag??
LD ($5C5F),HL ; preserve workspace pointer in dynamic X_PTR
EX DE,HL ; transfer program dest pointer to HL.
CALL L19B8 ; routine NEXT-ONE finds following location
; in program or variables area.
CALL L19E8 ; routine RECLAIM-2 reclaims the space between.
EX DE,HL ; transfer program dest pointer back to DE.
LD HL,($5C5F) ; fetch adjusted workspace pointer from X_PTR
EX AF,AF' ; restore flags.
; now the new line or variable is entered.
;; ME-ENT-1
L093E: EX AF,AF' ; save or re-save flags.
PUSH DE ; save dest pointer in prog/vars area.
CALL L19B8 ; routine NEXT-ONE finds next in workspace.
; gets next in DE, difference in BC.
; prev addr in HL
LD ($5C5F),HL ; store pointer in X_PTR
LD HL,($5C53) ; load HL from system variable PROG
EX (SP),HL ; swap with prog/vars pointer on stack.
PUSH BC ; ** save length of new program line/variable.
EX AF,AF' ; fetch flags back.
JR C,L0955 ; skip to ME-ENT-2 if variable
DEC HL ; address location before pointer
CALL L1655 ; routine MAKE-ROOM creates room for BASIC line
INC HL ; address next.
JR L0958 ; forward to ME-ENT-3
; ---
;; ME-ENT-2
L0955: CALL L1655 ; routine MAKE-ROOM creates room for variable.
;; ME-ENT-3
L0958: INC HL ; address next?
POP BC ; ** pop length
POP DE ; * pop value for PROG which may have been
; altered by POINTERS if first line.
LD ($5C53),DE ; set PROG to original value.
LD DE,($5C5F) ; fetch adjusted workspace pointer from X_PTR
PUSH BC ; save length
PUSH DE ; and workspace pointer
EX DE,HL ; make workspace pointer source, prog/vars
; pointer the destination
LDIR ; copy bytes of line or variable into new area.
POP HL ; restore workspace pointer.
POP BC ; restore length.
PUSH DE ; save new prog/vars pointer.
CALL L19E8 ; routine RECLAIM-2 reclaims the space used
; by the line or variable in workspace block
; as no longer required and space could be
; useful for adding more lines.
POP DE ; restore the prog/vars pointer
RET ; return.
; -------------------
; Handle SAVE control
; -------------------
; A branch from the main SAVE-ETC routine at SAVE-ALL.
; First the header data is saved. Then after a wait of 1 second
; the data itself is saved.
; HL points to start of data.
; IX points to start of descriptor.
;; SA-CONTRL
L0970: PUSH HL ; save start of data
LD A,$FD ; select system channel 'S'
CALL L1601 ; routine CHAN-OPEN
XOR A ; clear to address table directly
LD DE,L09A1 ; address: tape-msgs
CALL L0C0A ; routine PO-MSG -
; 'Start tape then press any key.'
SET 5,(IY+$02) ; TV_FLAG - Signal lower screen requires
; clearing
CALL L15D4 ; routine WAIT-KEY
PUSH IX ; save pointer to descriptor.
LD DE,$0011 ; there are seventeen bytes.
XOR A ; signal a header.
CALL L04C2 ; routine SA-BYTES
POP IX ; restore descriptor pointer.
LD B,$32 ; wait for a second - 50 interrupts.
;; SA-1-SEC
L0991: HALT ; wait for interrupt
DJNZ L0991 ; back to SA-1-SEC until pause complete.
LD E,(IX+$0B) ; fetch length of bytes from the
LD D,(IX+$0C) ; descriptor.
LD A,$FF ; signal data bytes.
POP IX ; retrieve pointer to start
JP L04C2 ; jump back to SA-BYTES
; Arrangement of two headers in workspace.
; Originally IX addresses first location and only one header is required
; when saving.
;
; OLD NEW PROG DATA DATA CODE
; HEADER HEADER num chr NOTES.
; ------ ------ ---- ---- ---- ---- -----------------------------
; IX-$11 IX+$00 0 1 2 3 Type.
; IX-$10 IX+$01 x x x x F ($FF if filename is null).
; IX-$0F IX+$02 x x x x i
; IX-$0E IX+$03 x x x x l
; IX-$0D IX+$04 x x x x e
; IX-$0C IX+$05 x x x x n
; IX-$0B IX+$06 x x x x a
; IX-$0A IX+$07 x x x x m
; IX-$09 IX+$08 x x x x e
; IX-$08 IX+$09 x x x x .
; IX-$07 IX+$0A x x x x (terminal spaces).
; IX-$06 IX+$0B lo lo lo lo Total
; IX-$05 IX+$0C hi hi hi hi Length of datablock.
; IX-$04 IX+$0D Auto - - Start Various
; IX-$03 IX+$0E Start a-z a-z addr ($80 if no autostart).
; IX-$02 IX+$0F lo - - - Length of Program
; IX-$01 IX+$10 hi - - - only i.e. without variables.
;
; ------------------------
; Canned cassette messages
; ------------------------
; The last-character-inverted Cassette messages.
; Starts with normal initial step-over byte.
;; tape-msgs
L09A1 DB $80
DC "Start tape, then press any key." ;DEFM "Start tape, then press any key"
L09C0 EQU $-1 ;DB '.'+$80
DB $0D
DC "Program: " ;DEFM "Program:"
;DB ' '+$80
DB $0D
DC "Number array: " ;DEFM "Number array:"
;DB ' '+$80
DB $0D
DC "Character array: " ;DEFM "Character array:"
;DB ' '+$80
DB $0D
DC "Bytes: " ;DEFM "Bytes:"
;DB ' '+$80
; DB ' '+$80
;**************************************************
;** Part 5. SCREEN AND PRINTER HANDLING ROUTINES **
;**************************************************
; ---------------------
; General PRINT routine
; ---------------------
; This is the routine most often used by the RST 10 restart although the
; subroutine is on two occasions called directly when it is known that
; output will definitely be to the lower screen.
;; PRINT-OUT
L09F4: CALL L0B03 ; routine PO-FETCH fetches print position
; to HL register pair.
CP $20 ; is character a space or higher ?
JP NC,L0AD9 ; jump forward to PO-ABLE if so.
CP $06 ; is character in range 00-05 ?
JR C,L0A69 ; to PO-QUEST to print '?' if so.
CP $18 ; is character in range 24d - 31d ?
JR NC,L0A69 ; to PO-QUEST to also print '?' if so.
LD HL,L0A11 - 6 ; address 0A0B - the base address of control
; character table - where zero would be.
LD E,A ; control character 06 - 23d
LD D,$00 ; is transferred to DE.
ADD HL,DE ; index into table.
LD E,(HL) ; fetch the offset to routine.
ADD HL,DE ; add to make HL the address.
PUSH HL ; push the address.
JP L0B03 ; to PO-FETCH, as the screen/printer position
; has been disturbed, and indirectly to
; routine on stack.
; -----------------------
; Control character table
; -----------------------
; For control characters in the range 6 - 23d the following table
; is indexed to provide an offset to the handling routine that
; follows the table.
;; ctlchrtab
L0A11: DB L0A5F - $ ; 06d offset $4E to Address: PO-COMMA
DB L0A69 - $ ; 07d offset $57 to Address: PO-QUEST
DB L0A23 - $ ; 08d offset $10 to Address: PO-BACK-1
DB L0A3D - $ ; 09d offset $29 to Address: PO-RIGHT
DB L0A69 - $ ; 10d offset $54 to Address: PO-QUEST
DB L0A69 - $ ; 11d offset $53 to Address: PO-QUEST
DB L0A69 - $ ; 12d offset $52 to Address: PO-QUEST
DB L0A4F - $ ; 13d offset $37 to Address: PO-ENTER
DB L0A69 - $ ; 14d offset $50 to Address: PO-QUEST
DB L0A69 - $ ; 15d offset $4F to Address: PO-QUEST
DB L0A7A - $ ; 16d offset $5F to Address: PO-1-OPER
DB L0A7A - $ ; 17d offset $5E to Address: PO-1-OPER
DB L0A7A - $ ; 18d offset $5D to Address: PO-1-OPER
DB L0A7A - $ ; 19d offset $5C to Address: PO-1-OPER
DB L0A7A - $ ; 20d offset $5B to Address: PO-1-OPER
DB L0A7A - $ ; 21d offset $5A to Address: PO-1-OPER
DB L0A75 - $ ; 22d offset $54 to Address: PO-2-OPER
DB L0A75 - $ ; 23d offset $53 to Address: PO-2-OPER
; -------------------
; Cursor left routine
; -------------------
; Backspace and up a line if that action is from the left of screen.
; For ZX printer backspace up to first column but not beyond.
;; PO-BACK-1
L0A23: INC C ; move left one column.
LD A,$22 ; value $21 is leftmost column.
CP C ; have we passed ?
JR NZ,L0A3A ; to PO-BACK-3 if not and store new position.
BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
JR NZ,L0A38 ; to PO-BACK-2 if so, as we are unable to
; backspace from the leftmost position.
INC B ; move up one screen line
LD C,$02 ; the rightmost column position.
LD A,$18 ; Note. This should be $19
; credit. Dr. Frank O'Hara, 1982
CP B ; has position moved past top of screen ?
JR NZ,L0A3A ; to PO-BACK-3 if not and store new position.
DEC B ; else back to $18.
;; PO-BACK-2
L0A38: LD C,$21 ; the leftmost column position.
;; PO-BACK-3
L0A3A: JP L0DD9 ; to CL-SET and PO-STORE to save new
; position in system variables.
; --------------------
; Cursor right routine
; --------------------
; This moves the print position to the right leaving a trail in the
; current background colour.
; "However the programmer has failed to store the new print position
; so CHR$ 9 will only work if the next print position is at a newly
; defined place.
; e.g. PRINT PAPER 2; CHR$ 9; AT 4,0;
; does work but is not very helpful"
; - Dr. Ian Logan, Understanding Your Spectrum, 1982.
;; PO-RIGHT
L0A3D: LD A,($5C91) ; fetch P_FLAG value
PUSH AF ; and save it on stack.
LD (IY+$57),$01 ; temporarily set P_FLAG 'OVER 1'.
LD A,$20 ; prepare a space.
CALL L0B65 ; routine PO-CHAR to print it.
; Note. could be PO-ABLE which would update
; the column position.
POP AF ; restore the permanent flag.
LD ($5C91),A ; and restore system variable P_FLAG
RET ; return without updating column position
; -----------------------
; Perform carriage return
; -----------------------
; A carriage return is 'printed' to screen or printer buffer.
;; PO-ENTER
L0A4F: BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
JP NZ,L0ECD ; to COPY-BUFF if so, to flush buffer and reset
; the print position.
LD C,$21 ; the leftmost column position.
CALL L0C55 ; routine PO-SCR handles any scrolling required.
DEC B ; to next screen line.
JP L0DD9 ; jump forward to CL-SET to store new position.
; -----------
; Print comma
; -----------
; The comma control character. The 32 column screen has two 16 character
; tabstops. The routine is only reached via the control character table.
;; PO-COMMA
L0A5F: CALL L0B03 ; routine PO-FETCH - seems unnecessary.
LD A,C ; the column position. $21-$01
DEC A ; move right. $20-$00
DEC A ; and again $1F-$00 or $FF if trailing
AND $10 ; will be $00 or $10.
JR L0AC3 ; forward to PO-FILL
; -------------------
; Print question mark
; -------------------
; This routine prints a question mark which is commonly
; used to print an unassigned control character in range 0-31d.
; there are a surprising number yet to be assigned.
;; PO-QUEST
L0A69: LD A,$3F ; prepare the character '?'.
JR L0AD9 ; forward to PO-ABLE.
; --------------------------------
; Control characters with operands
; --------------------------------
; Certain control characters are followed by 1 or 2 operands.
; The entry points from control character table are PO-2-OPER and PO-1-OPER.
; The routines alter the output address of the current channel so that
; subsequent RST $10 instructions take the appropriate action
; before finally resetting the output address back to PRINT-OUT.
;; PO-TV-2
L0A6D: LD DE,L0A87 ; address: PO-CONT will be next output routine
LD ($5C0F),A ; store first operand in TVDATA-hi
JR L0A80 ; forward to PO-CHANGE >>
; ---
; -> This initial entry point deals with two operands - AT or TAB.
;; PO-2-OPER
L0A75: LD DE,L0A6D ; address: PO-TV-2 will be next output routine
JR L0A7D ; forward to PO-TV-1
; ---
; -> This initial entry point deals with one operand INK to OVER.
;; PO-1-OPER
L0A7A: LD DE,L0A87 ; address: PO-CONT will be next output routine
;; PO-TV-1
L0A7D: LD ($5C0E),A ; store control code in TVDATA-lo
;; PO-CHANGE
L0A80: LD HL,($5C51) ; use CURCHL to find current output channel.
LD (HL),E ; make it
INC HL ; the supplied
LD (HL),D ; address from DE.
RET ; return.
; ---
;; PO-CONT
L0A87: LD DE,L09F4 ; Address: PRINT-OUT
CALL L0A80 ; routine PO-CHANGE to restore normal channel.
LD HL,($5C0E) ; TVDATA gives control code and possible
; subsequent character
LD D,A ; save current character
LD A,L ; the stored control code
CP $16 ; was it INK to OVER (1 operand) ?
JP C,L2211 ; to CO-TEMP-5
JR NZ,L0AC2 ; to PO-TAB if not 22d i.e. 23d TAB.
; else must have been 22d AT.
LD B,H ; line to H (0-23d)
LD C,D ; column to C (0-31d)
LD A,$1F ; the value 31d
SUB C ; reverse the column number.
JR C,L0AAC ; to PO-AT-ERR if C was greater than 31d.
ADD A,$02 ; transform to system range $02-$21
LD C,A ; and place in column register.
BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
JR NZ,L0ABF ; to PO-AT-SET as line can be ignored.
LD A,$16 ; 22 decimal
SUB B ; subtract line number to reverse
; 0 - 22 becomes 22 - 0.
;; PO-AT-ERR
L0AAC: JP C,L1E9F ; to REPORT-B if higher than 22 decimal
; Integer out of range.
INC A ; adjust for system range $01-$17
LD B,A ; place in line register
INC B ; adjust to system range $02-$18
BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ?
JP NZ,L0C55 ; exit to PO-SCR to test for scrolling
CP (IY+$31) ; Compare against DF_SZ
JP C,L0C86 ; to REPORT-5 if too low
; Out of screen.
;; PO-AT-SET
L0ABF: JP L0DD9 ; print position is valid so exit via CL-SET
; Continue here when dealing with TAB.
; Note. In BASIC, TAB is followed by a 16-bit number and was initially
; designed to work with any output device.
;; PO-TAB
L0AC2: LD A,H ; transfer parameter to A
; Losing current character -
; High byte of TAB parameter.
;; PO-FILL
L0AC3: CALL L0B03 ; routine PO-FETCH, HL-addr, BC=line/column.
; column 1 (right), $21 (left)
ADD A,C ; add operand to current column
DEC A ; range 0 - 31+
AND $1F ; make range 0 - 31d
RET Z ; return if result zero
LD D,A ; Counter to D
SET 0,(IY+$01) ; update FLAGS - signal suppress leading space.
;; PO-SPACE
L0AD0: LD A,$20 ; space character.
CALL L0C3B ; routine PO-SAVE prints the character
; using alternate set (normal output routine)
DEC D ; decrement counter.
JR NZ,L0AD0 ; to PO-SPACE until done
RET ; return
; ----------------------
; Printable character(s)
; ----------------------
; This routine prints printable characters and continues into
; the position store routine
;; PO-ABLE
L0AD9: CALL L0B24 ; routine PO-ANY
; and continue into position store routine.
; -------------------------------------
; Store line, column, and pixel address
; -------------------------------------
; This routine updates the system variables associated with
; The main screen, lower screen/input buffer or ZX printer.
;; PO-STORE
L0ADC: BIT 1,(IY+$01) ; test FLAGS - Is printer in use ?
JR NZ,L0AFC ; to PO-ST-PR if so
BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ?
JR NZ,L0AF0 ; to PO-ST-E if so
LD ($5C88),BC ; S_POSN line/column upper screen
LD ($5C84),HL ; DF_CC display file address
RET ;
; ---
;; PO-ST-E
L0AF0: LD ($5C8A),BC ; SPOSNL line/column lower screen
LD ($5C82),BC ; ECHO_E line/column input buffer
LD ($5C86),HL ; DFCCL lower screen memory address
RET ;
; ---
;; PO-ST-PR
L0AFC: LD (IY+$45),C ; P_POSN column position printer
LD ($5C80),HL ; PR_CC full printer buffer memory address
RET ;
; -------------------------
; Fetch position parameters
; -------------------------
; This routine fetches the line/column and display file address
; of the upper and lower screen or, if the printer is in use,
; the column position and absolute memory address.
; Note. that PR-CC-hi (23681) is used by this routine and the one above
; and if, in accordance with the manual (that says this is unused), the
; location has been used for other purposes, then subsequent output
; to the printer buffer could corrupt a 256-byte section of memory.
;; PO-FETCH
L0B03: BIT 1,(IY+$01) ; test FLAGS - Is printer in use
JR NZ,L0B1D ; to PO-F-PR if so
; assume upper screen
LD BC,($5C88) ; S_POSN
LD HL,($5C84) ; DF_CC display file address
BIT 0,(IY+$02) ; TV_FLAG - Lower screen in use ?
RET Z ; return if upper screen
; ah well, was lower screen
LD BC,($5C8A) ; SPOSNL
LD HL,($5C86) ; DFCCL
RET ; return
; ---
;; PO-F-PR
L0B1D: LD C,(IY+$45) ; P_POSN column only
LD HL,($5C80) ; PR_CC printer buffer address
RET ; return
; -------------------
; Print any character
; -------------------
; This routine is used to print any character in range 32d - 255d
; It is only called from PO-ABLE which continues into PO-STORE
;; PO-ANY
L0B24: CP $80 ; ASCII ?
JR C,L0B65 ; to PO-CHAR is so.
CP $90 ; test if a block graphic character.
JR NC,L0B52 ; to PO-T&UDG to print tokens and udg's
; The 16 2*2 mosaic characters 128-143 decimal are formed from
; bits 0-3 of the character.
LD B,A ; save character
CALL L0B38 ; routine PO-GR-1 to construct top half
; then bottom half.
CALL L0B03 ; routine PO-FETCH fetches print position.
LD DE,$5C92 ; MEM-0 is location of 8 bytes of character
JR L0B7F ; to PR-ALL to print to screen or printer
; ---
;; PO-GR-1
L0B38: LD HL,$5C92 ; address MEM-0 - a temporary buffer in
; systems variables which is normally used
; by the calculator.
CALL L0B3E ; routine PO-GR-2 to construct top half
; and continue into routine to construct
; bottom half.
;; PO-GR-2
L0B3E: RR B ; rotate bit 0/2 to carry
SBC A,A ; result $00 or $FF
AND $0F ; mask off right hand side
LD C,A ; store part in C
RR B ; rotate bit 1/3 of original chr to carry
SBC A,A ; result $00 or $FF
AND $F0 ; mask off left hand side
OR C ; combine with stored pattern
LD C,$04 ; four bytes for top/bottom half
;; PO-GR-3
L0B4C: LD (HL),A ; store bit patterns in temporary buffer
INC HL ; next address
DEC C ; jump back to
JR NZ,L0B4C ; to PO-GR-3 until byte is stored 4 times
RET ; return
; ---
; Tokens and User defined graphics are now separated.
;; PO-T&UDG
L0B52 IF BAS48_ONLY=1
SUB 0XA5
JR NC,L0B5F
ELSE
JP L3B9F ;Spectrum 128 patch
NOP
ENDIF
L0B56: ADD A,$15 ; add 21d to restore to 0 - 20
PUSH BC ; save current print position
LD BC,($5C7B) ; fetch UDG to address bit patterns
JR L0B6A ; to PO-CHAR-2 - common code to lay down
; a bit patterned character
; ---
;; PO-T
L0B5F: CALL L0C10 ; routine PO-TOKENS prints tokens
JP L0B03 ; exit via a JUMP to PO-FETCH as this routine
; must continue into PO-STORE.
; A JR instruction could be used.
; This point is used to print ASCII characters 32d - 127d.
;; PO-CHAR
L0B65: PUSH BC ; save print position
LD BC,($5C36) ; address CHARS
; This common code is used to transfer the character bytes to memory.
;; PO-CHAR-2
L0B6A: EX DE,HL ; transfer destination address to DE
LD HL,$5C3B ; point to FLAGS
RES 0,(HL) ; allow for leading space
CP $20 ; is it a space ?
JR NZ,L0B76 ; to PO-CHAR-3 if not
SET 0,(HL) ; signal no leading space to FLAGS
;; PO-CHAR-3
L0B76: LD H,$00 ; set high byte to 0
LD L,A ; character to A
; 0-21 UDG or 32-127 ASCII.
ADD HL,HL ; multiply
ADD HL,HL ; by
ADD HL,HL ; eight
ADD HL,BC ; HL now points to first byte of character
POP BC ; the source address CHARS or UDG
EX DE,HL ; character address to DE
; --------------------
; Print all characters
; --------------------
; This entry point entered from above to print ASCII and UDGs
; but also from earlier to print mosaic characters.
; HL=destination
; DE=character source
; BC=line/column
;; PR-ALL
L0B7F: LD A,C ; column to A
DEC A ; move right
LD A,$21 ; pre-load with leftmost position
JR NZ,L0B93 ; but if not zero to PR-ALL-1
DEC B ; down one line
LD C,A ; load C with $21
BIT 1,(IY+$01) ; test FLAGS - Is printer in use
JR Z,L0B93 ; to PR-ALL-1 if not
PUSH DE ; save source address
CALL L0ECD ; routine COPY-BUFF outputs line to printer
POP DE ; restore character source address
LD A,C ; the new column number ($21) to C
;; PR-ALL-1
L0B93: CP C ; this test is really for screen - new line ?
PUSH DE ; save source
CALL Z,L0C55 ; routine PO-SCR considers scrolling
POP DE ; restore source
PUSH BC ; save line/column
PUSH HL ; and destination
LD A,($5C91) ; fetch P_FLAG to accumulator
LD B,$FF ; prepare OVER mask in B.
RRA ; bit 0 set if OVER 1
JR C,L0BA4 ; to PR-ALL-2
INC B ; set OVER mask to 0
;; PR-ALL-2
L0BA4: RRA ; skip bit 1 of P_FLAG
RRA ; bit 2 is INVERSE
SBC A,A ; will be FF for INVERSE 1 else zero
LD C,A ; transfer INVERSE mask to C
LD A,$08 ; prepare to count 8 bytes
AND A ; clear carry to signal screen
BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
JR Z,L0BB6 ; to PR-ALL-3 if screen
SET 1,(IY+$30) ; update FLAGS2 - signal printer buffer has
; been used.
SCF ; set carry flag to signal printer.
;; PR-ALL-3
L0BB6: EX DE,HL ; now HL=source, DE=destination
;; PR-ALL-4
L0BB7: EX AF,AF' ; save printer/screen flag
LD A,(DE) ; fetch existing destination byte
AND B ; consider OVER
XOR (HL) ; now XOR with source
XOR C ; now with INVERSE MASK
LD (DE),A ; update screen/printer
EX AF,AF' ; restore flag
JR C,L0BD3 ; to PR-ALL-6 - printer address update
INC D ; gives next pixel line down screen
;; PR-ALL-5
L0BC1: INC HL ; address next character byte
DEC A ; the byte count is decremented
JR NZ,L0BB7 ; back to PR-ALL-4 for all 8 bytes
EX DE,HL ; destination to HL
DEC H ; bring back to last updated screen position
BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
CALL Z,L0BDB ; if not, call routine PO-ATTR to update
; corresponding colour attribute.
POP HL ; restore original screen/printer position
POP BC ; and line column
DEC C ; move column to right
INC HL ; increase screen/printer position
RET ; return and continue into PO-STORE
; within PO-ABLE
; ---
; This branch is used to update the printer position by 32 places
; Note. The high byte of the address D remains constant (which it should).
;; PR-ALL-6
L0BD3: EX AF,AF' ; save the flag
LD A,$20 ; load A with 32 decimal
ADD A,E ; add this to E
LD E,A ; and store result in E
EX AF,AF' ; fetch the flag
JR L0BC1 ; back to PR-ALL-5
; -------------
; Set attribute
; -------------
; This routine is entered with the HL register holding the last screen
; address to be updated by PRINT or PLOT.
; The Spectrum screen arrangement leads to the L register holding
; the correct value for the attribute file and it is only necessary
; to manipulate H to form the correct colour attribute address.
;; PO-ATTR
L0BDB: LD A,H ; fetch high byte $40 - $57
RRCA ; shift
RRCA ; bits 3 and 4
RRCA ; to right.
AND $03 ; range is now 0 - 2
OR $58 ; form correct high byte for third of screen
LD H,A ; HL is now correct
LD DE,($5C8F) ; make D hold ATTR_T, E hold MASK-T
LD A,(HL) ; fetch existing attribute
XOR E ; apply masks
AND D ;
XOR E ;
BIT 6,(IY+$57) ; test P_FLAG - is this PAPER 9 ??
JR Z,L0BFA ; skip to PO-ATTR-1 if not.
AND $C7 ; set paper
BIT 2,A ; to contrast with ink
JR NZ,L0BFA ; skip to PO-ATTR-1
XOR $38 ;
;; PO-ATTR-1
L0BFA: BIT 4,(IY+$57) ; test P_FLAG - Is this INK 9 ??
JR Z,L0C08 ; skip to PO-ATTR-2 if not
AND $F8 ; make ink
BIT 5,A ; contrast with paper.
JR NZ,L0C08 ; to PO-ATTR-2
XOR $07 ;
;; PO-ATTR-2
L0C08: LD (HL),A ; save the new attribute.
RET ; return.
; ----------------
; Message printing
; ----------------
; This entry point is used to print tape, boot-up, scroll? and error messages
; On entry the DE register points to an initial step-over byte or
; the inverted end-marker of the previous entry in the table.
; A contains the message number, often zero to print first message.
; (HL has nothing important usually P_FLAG)
;; PO-MSG
L0C0A: PUSH HL ; put hi-byte zero on stack to suppress
LD H,$00 ; trailing spaces
EX (SP),HL ; ld h,0; push hl would have done ?.
JR L0C14 ; forward to PO-TABLE.
; ---
; This entry point prints the BASIC keywords, '<>' etc. from alt set
;; PO-TOKENS
L0C10: LD DE,L0095 ; address: TKN-TABLE
PUSH AF ; save the token number to control
; trailing spaces - see later *
;; PO-TABLE
L0C14: CALL L0C41 ; routine PO-SEARCH will set carry for
; all messages and function words.
L0C17: JR C,L0C22 ; forward to PO-EACH if not a command,
; '<>' etc.
LD A,$20 ; prepare leading space
BIT 0,(IY+$01) ; test FLAGS - leading space if not set
CALL Z,L0C3B ; routine PO-SAVE to print a space
; without disturbing registers
;; PO-EACH
L0C22: LD A,(DE) ; fetch character
AND $7F ; remove any inverted bit
CALL L0C3B ; routine PO-SAVE to print using alternate
; set of registers.
LD A,(DE) ; re-fetch character.
INC DE ; address next
ADD A,A ; was character inverted ?
; (this also doubles character)
JR NC,L0C22 ; back to PO-EACH if not
POP DE ; * re-fetch trailing space flag to D (was A)
CP $48 ; was last character '$' ($24*2)
JR Z,L0C35 ; forward to PO-TR-SP to consider trailing
; space if so.
CP $82 ; was it < 'A' i.e. '#','>','=' from tokens
; or ' ','.' (from tape) or '?' from scroll
RET C ; no trailing space
;; PO-TR-SP
L0C35: LD A,D ; the trailing space flag (zero if an error msg)
CP $03 ; test against RND, INKEY$ and PI
; which have no parameters and
RET C ; therefore no trailing space so return.
LD A,$20 ; else continue and print a trailing space.
; -------------------------
; Handle recursive printing
; -------------------------
; This routine which is part of PRINT-OUT allows RST $10 to be
; used recursively to print tokens and the spaces associated with them.
;; PO-SAVE
L0C3B: PUSH DE ; save DE as CALL-SUB doesn't.
EXX ; switch in main set
RST 10H ; PRINT-A prints using this alternate set.
EXX ; back to this alternate set.
POP DE ; restore initial DE.
RET ; return.
; ------------
; Table search
; ------------
; This subroutine searches a message or the token table for the
; message number held in A. DE holds the address of the table.
;; PO-SEARCH
L0C41: PUSH AF ; save the message/token number
EX DE,HL ; transfer DE to HL
INC A ; adjust for initial step-over byte
;; PO-STEP
L0C44: BIT 7,(HL) ; is character inverted ?
INC HL ; address next
JR Z,L0C44 ; back to PO-STEP if not inverted.
DEC A ; decrease counter
JR NZ,L0C44 ; back to PO-STEP if not zero
EX DE,HL ; transfer address to DE
POP AF ; restore message/token number
CP $20 ; return with carry set
RET C ; for all messages and function tokens
LD A,(DE) ; test first character of token
SUB $41 ; and return with carry set
RET ; if it is less that 'A'
; i.e. '<>', '<=', '>='
; ---------------
; Test for scroll
; ---------------
; This test routine is called when printing carriage return, when considering
; PRINT AT and from the general PRINT ALL characters routine to test if
; scrolling is required, prompting the user if necessary.
; This is therefore using the alternate set.
; The B register holds the current line.
;; PO-SCR
L0C55: BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
RET NZ ; return immediately if so.
LD DE,L0DD9 ; set DE to address: CL-SET
PUSH DE ; and push for return address.
LD A,B ; transfer the line to A.
BIT 0,(IY+$02) ; test TV_FLAG - Lower screen in use ?
JP NZ,L0D02 ; jump forward to PO-SCR-4 if so.
CP (IY+$31) ; greater than DF_SZ display file size ?
JR C,L0C86 ; forward to REPORT-5 if less.
; 'Out of screen'
RET NZ ; return (via CL-SET) if greater
BIT 4,(IY+$02) ; test TV_FLAG - Automatic listing ?
JR Z,L0C88 ; forward to PO-SCR-2 if not.
LD E,(IY+$2D) ; fetch BREG - the count of scroll lines to E.
DEC E ; decrease and jump
JR Z,L0CD2 ; to PO-SCR-3 if zero and scrolling required.
LD A,$00 ; explicit - select channel zero.
CALL L1601 ; routine CHAN-OPEN opens it.
LD SP,($5C3F) ; set stack pointer to LIST_SP
RES 4,(IY+$02) ; reset TV_FLAG - signal auto listing finished.
RET ; return ignoring pushed value, CL-SET
; to MAIN or EDITOR without updating
; print position ->
; ---
;; REPORT-5
L0C86: RST 08H ; ERROR-1
DB $04 ; Error Report: Out of screen
; continue here if not an automatic listing.
;; PO-SCR-2
L0C88: DEC (IY+$52) ; decrease SCR_CT
JR NZ,L0CD2 ; forward to PO-SCR-3 to scroll display if
; result not zero.
; now produce prompt.
LD A,$18 ; reset
SUB B ; the
LD ($5C8C),A ; SCR_CT scroll count
LD HL,($5C8F) ; L=ATTR_T, H=MASK_T
PUSH HL ; save on stack
LD A,($5C91) ; P_FLAG
PUSH AF ; save on stack to prevent lower screen
; attributes (BORDCR etc.) being applied.
LD A,$FD ; select system channel 'K'
CALL L1601 ; routine CHAN-OPEN opens it
XOR A ; clear to address message directly
LD DE,L0CF8 ; make DE address: scrl-mssg
CALL L0C0A ; routine PO-MSG prints to lower screen
SET 5,(IY+$02) ; set TV_FLAG - signal lower screen requires
; clearing
LD HL,$5C3B ; make HL address FLAGS
SET 3,(HL) ; signal 'L' mode.
RES 5,(HL) ; signal 'no new key'.
EXX ; switch to main set.
; as calling chr input from alternative set.
CALL L15D4 ; routine WAIT-KEY waits for new key
; Note. this is the right routine but the
; stream in use is unsatisfactory. From the
; choices available, it is however the best.
EXX ; switch back to alternate set.
CP $20 ; space is considered as BREAK
JR Z,L0D00 ; forward to REPORT-D if so
; 'BREAK - CONT repeats'
CP $E2 ; is character 'STOP' ?
JR Z,L0D00 ; forward to REPORT-D if so
OR $20 ; convert to lower-case
CP $6E ; is character 'n' ?
JR Z,L0D00 ; forward to REPORT-D if so else scroll.
LD A,$FE ; select system channel 'S'
CALL L1601 ; routine CHAN-OPEN
POP AF ; restore original P_FLAG
LD ($5C91),A ; and save in P_FLAG.
POP HL ; restore original ATTR_T, MASK_T
LD ($5C8F),HL ; and reset ATTR_T, MASK-T as 'scroll?' has
; been printed.
;; PO-SCR-3
L0CD2: CALL L0DFE ; routine CL-SC-ALL to scroll whole display
LD B,(IY+$31) ; fetch DF_SZ to B
INC B ; increase to address last line of display
LD C,$21 ; set C to $21 (was $21 from above routine)
PUSH BC ; save the line and column in BC.
CALL L0E9B ; routine CL-ADDR finds display address.
LD A,H ; now find the corresponding attribute byte
RRCA ; (this code sequence is used twice
RRCA ; elsewhere and is a candidate for
RRCA ; a subroutine.)
AND $03 ;
OR $58 ;
LD H,A ;
LD DE,$5AE0 ; start of last 'line' of attribute area
LD A,(DE) ; get attribute for last line
LD C,(HL) ; transfer to base line of upper part
LD B,$20 ; there are thirty two bytes
EX DE,HL ; swap the pointers.
;; PO-SCR-3A
L0CF0: LD (DE),A ; transfer
LD (HL),C ; attributes.
INC DE ; address next.
INC HL ; address next.
DJNZ L0CF0 ; loop back to PO-SCR-3A for all adjacent
; attribute lines.
POP BC ; restore the line/column.
RET ; return via CL-SET (was pushed on stack).
; ---
; The message 'scroll?' appears here with last byte inverted.
;; scrl-mssg
L0CF8 DB $80 ; initial step-over byte.
DC "scroll?" ;DEFM "scroll"
;DB '?'+$80
;; REPORT-D
L0D00: RST 08H ; ERROR-1
DB $0C ; Error Report: BREAK - CONT repeats
; continue here if using lower display - A holds line number.
;; PO-SCR-4
L0D02: CP $02 ; is line number less than 2 ?
JR C,L0C86 ; to REPORT-5 if so
; 'Out of Screen'.
ADD A,(IY+$31) ; add DF_SZ
SUB $19 ;
RET NC ; return if scrolling unnecessary
NEG ; Negate to give number of scrolls required.
PUSH BC ; save line/column
LD B,A ; count to B
LD HL,($5C8F) ; fetch current ATTR_T, MASK_T to HL.
PUSH HL ; and save
LD HL,($5C91) ; fetch P_FLAG
PUSH HL ; and save.
; to prevent corruption by input AT
CALL L0D4D ; routine TEMPS sets to BORDCR etc
LD A,B ; transfer scroll number to A.
;; PO-SCR-4A
L0D1C: PUSH AF ; save scroll number.
LD HL,$5C6B ; address DF_SZ
LD B,(HL) ; fetch old value
LD A,B ; transfer to A
INC A ; and increment
LD (HL),A ; then put back.
LD HL,$5C89 ; address S_POSN_hi - line
CP (HL) ; compare
JR C,L0D2D ; forward to PO-SCR-4B if scrolling required
INC (HL) ; else increment S_POSN_hi
LD B,$18 ; set count to whole display ??
; Note. should be $17 and the top line
; will be scrolled into the ROM which
; is harmless on the standard set up.
;; PO-SCR-4B
L0D2D: CALL L0E00 ; routine CL-SCROLL scrolls B lines
POP AF ; restore scroll counter.
DEC A ; decrease
JR NZ,L0D1C ; back to to PO-SCR-4A until done
POP HL ; restore original P_FLAG.
LD (IY+$57),L ; and overwrite system variable P_FLAG.
POP HL ; restore original ATTR_T/MASK_T.
LD ($5C8F),HL ; and update system variables.
LD BC,($5C88) ; fetch S_POSN to BC.
RES 0,(IY+$02) ; signal to TV_FLAG - main screen in use.
CALL L0DD9 ; call routine CL-SET for upper display.
SET 0,(IY+$02) ; signal to TV_FLAG - lower screen in use.
POP BC ; restore line/column
RET ; return via CL-SET for lower display.
; ----------------------
; Temporary colour items
; ----------------------
; This subroutine is called 11 times to copy the permanent colour items
; to the temporary ones.
;; TEMPS
L0D4D: XOR A ; clear the accumulator
LD HL,($5C8D) ; fetch L=ATTR_P and H=MASK_P
BIT 0,(IY+$02) ; test TV_FLAG - is lower screen in use ?
JR Z,L0D5B ; skip to TEMPS-1 if not
LD H,A ; set H, MASK P, to 00000000.
LD L,(IY+$0E) ; fetch BORDCR to L which is used for lower
; screen.
;; TEMPS-1
L0D5B: LD ($5C8F),HL ; transfer values to ATTR_T and MASK_T
; for the print flag the permanent values are odd bits, temporary even bits.
LD HL,$5C91 ; address P_FLAG.
JR NZ,L0D65 ; skip to TEMPS-2 if lower screen using A=0.
LD A,(HL) ; else pick up flag bits.
RRCA ; rotate permanent bits to temporary bits.
;; TEMPS-2
L0D65: XOR (HL) ;
AND $55 ; BIN 01010101
XOR (HL) ; permanent now as original
LD (HL),A ; apply permanent bits to temporary bits.
RET ; and return.
; ------------------
; Handle CLS command
; ------------------
; clears the display.
; if it's difficult to write it should be difficult to read.
;; CLS
L0D6B: CALL L0DAF ; routine CL-ALL clears display and
; resets attributes to permanent.
; re-attaches it to this computer.
; this routine called from INPUT, **
;; CLS-LOWER
L0D6E: LD HL,$5C3C ; address System Variable TV_FLAG.
RES 5,(HL) ; TV_FLAG - signal do not clear lower screen.
SET 0,(HL) ; TV_FLAG - signal lower screen in use.
CALL L0D4D ; routine TEMPS picks up temporary colours.
LD B,(IY+$31) ; fetch lower screen DF_SZ
CALL L0E44 ; routine CL-LINE clears lower part
; and sets permanent attributes.
LD HL,$5AC0 ; fetch attribute address leftmost cell,
; second line up.
LD A,($5C8D) ; fetch permanent attribute from ATTR_P.
DEC B ; decrement lower screen display file size
JR L0D8E ; forward to CLS-3 ->
; ---
;; CLS-1
L0D87: LD C,$20 ; set counter to 32 characters per line
;; CLS-2
L0D89: DEC HL ; decrease attribute address.
LD (HL),A ; and place attributes in next line up.
DEC C ; decrease 32 counter.
JR NZ,L0D89 ; loop back to CLS-2 until all 32 done.
;; CLS-3
L0D8E: DJNZ L0D87 ; decrease B counter and back to CLS-1
; if not zero.
LD (IY+$31),$02 ; set DF_SZ lower screen to 2
; This entry point is called from CL-ALL below to
; reset the system channel input and output addresses to normal.
;; CL-CHAN
L0D94: LD A,$FD ; select system channel 'K'
CALL L1601 ; routine CHAN-OPEN opens it.
LD HL,($5C51) ; fetch CURCHL to HL to address current channel
LD DE,L09F4 ; set address to PRINT-OUT for first pass.
AND A ; clear carry for first pass.
;; CL-CHAN-A
L0DA0: LD (HL),E ; insert output address first pass.
INC HL ; or input address on second pass.
LD (HL),D ;
INC HL ;
LD DE,L10A8 ; fetch address KEY-INPUT for second pass
CCF ; complement carry flag - will set on pass 1.
JR C,L0DA0 ; back to CL-CHAN-A if first pass else done.
LD BC,$1721 ; line 23 for lower screen
JR L0DD9 ; exit via CL-SET to set column
; for lower display
; ---------------------------
; Clearing whole display area
; ---------------------------
; This subroutine called from CLS, AUTO-LIST and MAIN-3
; clears 24 lines of the display and resets the relevant system variables
; and system channels.
;; CL-ALL
L0DAF: LD HL,$0000 ; initialize plot coordinates.
LD ($5C7D),HL ; set COORDS to 0,0.
RES 0,(IY+$30) ; update FLAGS2 - signal main screen is clear.
CALL L0D94 ; routine CL-CHAN makes channel 'K' 'normal'.
LD A,$FE ; select system channel 'S'
CALL L1601 ; routine CHAN-OPEN opens it
CALL L0D4D ; routine TEMPS picks up permanent values.
LD B,$18 ; There are 24 lines.
CALL L0E44 ; routine CL-LINE clears 24 text lines
; (and sets BC to $1821)
LD HL,($5C51) ; fetch CURCHL make HL address current
; channel 'S'
LD DE,L09F4 ; address: PRINT-OUT
LD (HL),E ; is made
INC HL ; the normal
LD (HL),D ; output address.
LD (IY+$52),$01 ; set SCR_CT - scroll count is set to default.
; Note. BC already contains $1821.
LD BC,$1821 ; reset column and line to 0,0
; and continue into CL-SET, below, exiting
; via PO-STORE (for upper screen).
; ---------------------------
; Set line and column numbers
; ---------------------------
; This important subroutine is used to calculate the character output
; address for screens or printer based on the line/column for screens
; or the column for printer.
;; CL-SET
L0DD9: LD HL,$5B00 ; the base address of printer buffer
BIT 1,(IY+$01) ; test FLAGS - is printer in use ?
JR NZ,L0DF4 ; forward to CL-SET-2 if so.
LD A,B ; transfer line to A.
BIT 0,(IY+$02) ; test TV_FLAG - lower screen in use ?
JR Z,L0DEE ; skip to CL-SET-1 if handling upper part
ADD A,(IY+$31) ; add DF_SZ for lower screen
SUB $18 ; and adjust.
;; CL-SET-1
L0DEE: PUSH BC ; save the line/column.
LD B,A ; transfer line to B
; (adjusted if lower screen)
CALL L0E9B ; routine CL-ADDR calculates address at left
; of screen.
POP BC ; restore the line/column.
;; CL-SET-2
L0DF4: LD A,$21 ; the column $1-$21 is reversed
SUB C ; to range $00 - $20
LD E,A ; now transfer to DE
LD D,$00 ; prepare for addition
ADD HL,DE ; and add to base address
JP L0ADC ; exit via PO-STORE to update relevant
; system variables.
; ----------------
; Handle scrolling
; ----------------
; The routine CL-SC-ALL is called once from PO to scroll all the display
; and from the routine CL-SCROLL, once, to scroll part of the display.
;; CL-SC-ALL
L0DFE: LD B,$17 ; scroll 23 lines, after 'scroll?'.
;; CL-SCROLL
L0E00: CALL L0E9B ; routine CL-ADDR gets screen address in HL.
LD C,$08 ; there are 8 pixel lines to scroll.
;; CL-SCR-1
L0E05: PUSH BC ; save counters.
PUSH HL ; and initial address.
LD A,B ; get line count.
AND $07 ; will set zero if all third to be scrolled.
LD A,B ; re-fetch the line count.
JR NZ,L0E19 ; forward to CL-SCR-3 if partial scroll.
; HL points to top line of third and must be copied to bottom of previous 3rd.
; ( so HL = $4800 or $5000 ) ( but also sometimes $4000 )
;; CL-SCR-2
L0E0D: EX DE,HL ; copy HL to DE.
LD HL,$F8E0 ; subtract $08 from H and add $E0 to L -
ADD HL,DE ; to make destination bottom line of previous
; third.
EX DE,HL ; restore the source and destination.
LD BC,$0020 ; thirty-two bytes are to be copied.
DEC A ; decrement the line count.
LDIR ; copy a pixel line to previous third.
;; CL-SCR-3
L0E19: EX DE,HL ; save source in DE.
LD HL,$FFE0 ; load the value -32.
ADD HL,DE ; add to form destination in HL.
EX DE,HL ; switch source and destination
LD B,A ; save the count in B.
AND $07 ; mask to find count applicable to current
RRCA ; third and
RRCA ; multiply by
RRCA ; thirty two (same as 5 RLCAs)
LD C,A ; transfer byte count to C ($E0 at most)
LD A,B ; store line count to A
LD B,$00 ; make B zero
LDIR ; copy bytes (BC=0, H incremented, L=0)
LD B,$07 ; set B to 7, C is zero.
ADD HL,BC ; add 7 to H to address next third.
AND $F8 ; has last third been done ?
JR NZ,L0E0D ; back to CL-SCR-2 if not
POP HL ; restore topmost address.
INC H ; next pixel line down.
POP BC ; restore counts.
DEC C ; reduce pixel line count.
JR NZ,L0E05 ; back to CL-SCR-1 if all eight not done.
CALL L0E88 ; routine CL-ATTR gets address in attributes
; from current 'ninth line', count in BC.
LD HL,$FFE0 ; set HL to the 16-bit value -32.
ADD HL,DE ; and add to form destination address.
EX DE,HL ; swap source and destination addresses.
LDIR ; copy bytes scrolling the linear attributes.
LD B,$01 ; continue to clear the bottom line.
; ---------------------------
; Clear text lines of display
; ---------------------------
; This subroutine, called from CL-ALL, CLS-LOWER and AUTO-LIST and above,
; clears text lines at bottom of display.
; The B register holds on entry the number of lines to be cleared 1-24.
;; CL-LINE
L0E44: PUSH BC ; save line count
CALL L0E9B ; routine CL-ADDR gets top address
LD C,$08 ; there are eight screen lines to a text line.
;; CL-LINE-1
L0E4A: PUSH BC ; save pixel line count
PUSH HL ; and save the address
LD A,B ; transfer the line to A (1-24).
;; CL-LINE-2
L0E4D: AND $07 ; mask 0-7 to consider thirds at a time
RRCA ; multiply
RRCA ; by 32 (same as five RLCA instructions)
RRCA ; now 32 - 256(0)
LD C,A ; store result in C
LD A,B ; save line in A (1-24)
LD B,$00 ; set high byte to 0, prepare for ldir.
DEC C ; decrement count 31-255.
LD D,H ; copy HL
LD E,L ; to DE.
LD (HL),$00 ; blank the first byte.
INC DE ; make DE point to next byte.
LDIR ; ldir will clear lines.
LD DE,$0701 ; now address next third adjusting
ADD HL,DE ; register E to address left hand side
DEC A ; decrease the line count.
AND $F8 ; will be 16, 8 or 0 (AND $18 will do).
LD B,A ; transfer count to B.
JR NZ,L0E4D ; back to CL-LINE-2 if 16 or 8 to do
; the next third.
POP HL ; restore start address.
INC H ; address next line down.
POP BC ; fetch counts.
DEC C ; decrement pixel line count
JR NZ,L0E4A ; back to CL-LINE-1 till all done.
CALL L0E88 ; routine CL-ATTR gets attribute address
; in DE and B * 32 in BC.
LD H,D ; transfer the address
LD L,E ; to HL.
INC DE ; make DE point to next location.
LD A,($5C8D) ; fetch ATTR_P - permanent attributes
BIT 0,(IY+$02) ; test TV_FLAG - lower screen in use ?
JR Z,L0E80 ; skip to CL-LINE-3 if not.
LD A,($5C48) ; else lower screen uses BORDCR as attribute.
;; CL-LINE-3
L0E80: LD (HL),A ; put attribute in first byte.
DEC BC ; decrement the counter.
LDIR ; copy bytes to set all attributes.
POP BC ; restore the line $01-$24.
LD C,$21 ; make column $21. (No use is made of this)
RET ; return to the calling routine.
; ------------------
; Attribute handling
; ------------------
; This subroutine is called from CL-LINE or CL-SCROLL with the HL register
; pointing to the 'ninth' line and H needs to be decremented before or after
; the division. Had it been done first then either present code or that used
; at the start of PO-ATTR could have been used.
; The Spectrum screen arrangement leads to the L register holding already
; the correct value for the attribute file and it is only necessary
; to manipulate H to form the correct colour attribute address.
;; CL-ATTR
L0E88: LD A,H ; fetch H to A - $48, $50, or $58.
RRCA ; divide by
RRCA ; eight.
RRCA ; $09, $0A or $0B.
DEC A ; $08, $09 or $0A.
OR $50 ; $58, $59 or $5A.
LD H,A ; save high byte of attributes.
EX DE,HL ; transfer attribute address to DE
LD H,C ; set H to zero - from last LDIR.
LD L,B ; load L with the line from B.
ADD HL,HL ; multiply
ADD HL,HL ; by
ADD HL,HL ; thirty two
ADD HL,HL ; to give count of attribute
ADD HL,HL ; cells to end of display.
LD B,H ; transfer result
LD C,L ; to register BC.
RET ; and return.
; -------------------------------
; Handle display with line number
; -------------------------------
; This subroutine is called from four places to calculate the address
; of the start of a screen character line which is supplied in B.
;; CL-ADDR
L0E9B: LD A,$18 ; reverse the line number
SUB B ; to range $00 - $17.
LD D,A ; save line in D for later.
RRCA ; multiply
RRCA ; by
RRCA ; thirty-two.
AND $E0 ; mask off low bits to make
LD L,A ; L a multiple of 32.
LD A,D ; bring back the line to A.
AND $18 ; now $00, $08 or $10.
OR $40 ; add the base address of screen.
LD H,A ; HL now has the correct address.
RET ; return.
; -------------------
; Handle COPY command
; -------------------
; This command copies the top 176 lines to the ZX Printer
; It is popular to call this from machine code at point
; L0EAF with B holding 192 (and interrupts disabled) for a full-screen
; copy. This particularly applies to 16K Spectrums as time-critical
; machine code routines cannot be written in the first 16K of RAM as
; it is shared with the ULA which has precedence over the Z80 chip.
;; COPY
L0EAC: DI ; disable interrupts as this is time-critical.
;===============================
RST 8
DB _AY_PRN_SCR
; LD B,$B0 ; top 176 lines.
;===============================
L0EAF LD HL,$4000 ; address start of the display file.
; now enter a loop to handle each pixel line.
;; COPY-1
L0EB2: PUSH HL ; save the screen address.
PUSH BC ; and the line counter.
CALL L0EF4 ; routine COPY-LINE outputs one line.
POP BC ; restore the line counter.
POP HL ; and display address.
INC H ; next line down screen within 'thirds'.
LD A,H ; high byte to A.
AND $07 ; result will be zero if we have left third.
JR NZ,L0EC9 ; forward to COPY-2 if not to continue loop.
LD A,L ; consider low byte first.
ADD A,$20 ; increase by 32 - sets carry if back to zero.
LD L,A ; will be next group of 8.
CCF ; complement - carry set if more lines in
; the previous third.
SBC A,A ; will be FF, if more, else 00.
AND $F8 ; will be F8 (-8) or 00.
ADD A,H ; that is subtract 8, if more to do in third.
LD H,A ; and reset address.
;; COPY-2
L0EC9: DJNZ L0EB2 ; back to COPY-1 for all lines.
JR L0EDA ; forward to COPY-END to switch off the printer
; motor and enable interrupts.
; Note. Nothing else required.
; ------------------------------
; Pass printer buffer to printer
; ------------------------------
; This routine is used to copy 8 text lines from the printer buffer
; to the ZX Printer. These text lines are mapped linearly so HL does
; not need to be adjusted at the end of each line.
;; COPY-BUFF
L0ECD: DI ; disable interrupts
LD HL,$5B00 ; the base address of the Printer Buffer.
LD B,$08 ; set count to 8 lines of 32 bytes.
;; COPY-3
L0ED3: PUSH BC ; save counter.
CALL L0EF4 ; routine COPY-LINE outputs 32 bytes
POP BC ; restore counter.
DJNZ L0ED3 ; loop back to COPY-3 for all 8 lines.
; then stop motor and clear buffer.
; Note. the COPY command rejoins here, essentially to execute the next
; three instructions.
;; COPY-END
L0EDA LD A,$04 ; output value 4 to port
OUT ($FB),A ; to stop the slowed printer motor.
L0EDE EI ; enable interrupts.
; --------------------
; Clear Printer Buffer
; --------------------
; This routine clears an arbitrary 256 bytes of memory.
; Note. The routine seems designed to clear a buffer that follows the
; system variables.
; The routine should check a flag or HL address and simply return if COPY
; is in use.
; (T-ADDR-lo would work for the system but not if COPY called externally.)
; As a consequence of this omission the buffer will needlessly
; be cleared when COPY is used and the screen/printer position may be set to
; the start of the buffer and the line number to 0 (B)
; giving an 'Out of Screen' error.
; There seems to have been an unsuccessful attempt to circumvent the use
; of PR_CC_hi.
;; CLEAR-PRB
L0EDF: LD HL,$5B00 ; the location of the buffer.
LD (IY+$46),L ; update PR_CC_lo - set to zero - superfluous.
XOR A ; clear the accumulator.
LD B,A ; set count to 256 bytes.
;; PRB-BYTES
L0EE7: LD (HL),A ; set addressed location to zero.
INC HL ; address next byte - Note. not INC L.
DJNZ L0EE7 ; back to PRB-BYTES. repeat for 256 bytes.
RES 1,(IY+$30) ; set FLAGS2 - signal printer buffer is clear.
LD C,$21 ; set the column position .
JP L0DD9 ; exit via CL-SET and then PO-STORE.
; -----------------
; Copy line routine
; -----------------
; This routine is called from COPY and COPY-BUFF to output a line of
; 32 bytes to the ZX Printer.
; Output to port $FB -
; bit 7 set - activate stylus.
; bit 7 low - deactivate stylus.
; bit 2 set - stops printer.
; bit 2 reset - starts printer
; bit 1 set - slows printer.
; bit 1 reset - normal speed.
;; COPY-LINE
;===============================
L0EF4
LD A,(HL)
RST 8
DB _AY_PRN_A_
RET
; LD A,B ; fetch the counter 1-8 or 1-176
; CP $03 ; is it 01 or 02 ?.
; SBC A,A ; result is $FF if so else $00.
;===============================
AND $02 ; result is 02 now else 00.
; bit 1 set slows the printer.
OUT ($FB),A ; slow the printer for the
; last two lines.
LD D,A ; save the mask to control the printer later.
;; COPY-L-1
L0EFD: CALL L1F54 ; call BREAK-KEY to read keyboard immediately.
JR C,L0F0C ; forward to COPY-L-2 if 'break' not pressed.
LD A,$04 ; else stop the
OUT ($FB),A ; printer motor.
EI ; enable interrupts.
CALL L0EDF ; call routine CLEAR-PRB.
; Note. should not be cleared if COPY in use.
;; REPORT-Dc
L0F0A: RST 08H ; ERROR-1
DB $0C ; Error Report: BREAK - CONT repeats
;; COPY-L-2
L0F0C: IN A,($FB) ; test now to see if
ADD A,A ; a printer is attached.
RET M ; return if not - but continue with parent
; command.
JR NC,L0EFD ; back to COPY-L-1 if stylus of printer not
; in position.
LD C,$20 ; set count to 32 bytes.
;; COPY-L-3
L0F14: LD E,(HL) ; fetch a byte from line.
INC HL ; address next location. Note. not INC L.
LD B,$08 ; count the bits.
;; COPY-L-4
L0F18: RL D ; prepare mask to receive bit.
RL E ; rotate leftmost print bit to carry
RR D ; and back to bit 7 of D restoring bit 1
;; COPY-L-5
L0F1E: IN A,($FB) ; read the port.
RRA ; bit 0 to carry.
JR NC,L0F1E ; back to COPY-L-5 if stylus not in position.
LD A,D ; transfer command bits to A.
OUT ($FB),A ; and output to port.
DJNZ L0F18 ; loop back to COPY-L-4 for all 8 bits.
DEC C ; decrease the byte count.
JR NZ,L0F14 ; back to COPY-L-3 until 256 bits done.
RET ; return to calling routine COPY/COPY-BUFF.
; ----------------------------------
; Editor routine for BASIC and INPUT
; ----------------------------------
; The editor is called to prepare or edit a BASIC line.
; It is also called from INPUT to input a numeric or string expression.
; The behaviour and options are quite different in the various modes
; and distinguished by bit 5 of FLAGX.
;
; This is a compact and highly versatile routine.
;; EDITOR
L0F2C: LD HL,($5C3D) ; fetch ERR_SP
PUSH HL ; save on stack
;; ED-AGAIN
L0F30: LD HL,L107F ; address: ED-ERROR
PUSH HL ; save address on stack and
LD ($5C3D),SP ; make ERR_SP point to it.
; Note. While in editing/input mode should an error occur then RST 08 will
; update X_PTR to the location reached by CH_ADD and jump to ED-ERROR
; where the error will be cancelled and the loop begin again from ED-AGAIN
; above. The position of the error will be apparent when the lower screen is
; reprinted. If no error then the re-iteration is to ED-LOOP below when
; input is arriving from the keyboard.
;; ED-LOOP
L0F38: CALL L15D4 ; routine WAIT-KEY gets key possibly
; changing the mode.
PUSH AF ; save key.
LD D,$00 ; and give a short click based
LD E,(IY-$01) ; on PIP value for duration.
LD HL,$00C8 ; and pitch.
CALL L03B5 ; routine BEEPER gives click - effective
; with rubber keyboard.
POP AF ; get saved key value.
LD HL,L0F38 ; address: ED-LOOP is loaded to HL.
PUSH HL ; and pushed onto stack.
; At this point there is a looping return address on the stack, an error
; handler and an input stream set up to supply characters.
; The character that has been received can now be processed.
CP $18 ; range 24 to 255 ?
JR NC,L0F81 ; forward to ADD-CHAR if so.
CP $07 ; lower than 7 ?
JR C,L0F81 ; forward to ADD-CHAR also.
; Note. This is a 'bug' and chr$ 6, the comma
; control character, should have had an
; entry in the ED-KEYS table.
; Steven Vickers, 1984, Pitman.
CP $10 ; less than 16 ?
JR C,L0F92 ; forward to ED-KEYS if editing control
; range 7 to 15 dealt with by a table
LD BC,$0002 ; prepare for ink/paper etc.
LD D,A ; save character in D
CP $16 ; is it ink/paper/bright etc. ?
JR C,L0F6C ; forward to ED-CONTR if so
; leaves 22d AT and 23d TAB
; which can't be entered via KEY-INPUT.
; so this code is never normally executed
; when the keyboard is used for input.
INC BC ; if it was AT/TAB - 3 locations required
BIT 7,(IY+$37) ; test FLAGX - Is this INPUT LINE ?
JP Z,L101E ; jump to ED-IGNORE if not, else
CALL L15D4 ; routine WAIT-KEY - input address is KEY-NEXT
; but is reset to KEY-INPUT
LD E,A ; save first in E
;; ED-CONTR
L0F6C: CALL L15D4 ; routine WAIT-KEY for control.
; input address will be key-next.
PUSH DE ; saved code/parameters
LD HL,($5C5B) ; fetch address of keyboard cursor from K_CUR
RES 0,(IY+$07) ; set MODE to 'L'
CALL L1655 ; routine MAKE-ROOM makes 2/3 spaces at cursor
POP BC ; restore code/parameters
INC HL ; address first location
LD (HL),B ; place code (ink etc.)
INC HL ; address next
LD (HL),C ; place possible parameter. If only one
; then DE points to this location also.
JR L0F8B ; forward to ADD-CH-1
; ------------------------
; Add code to current line
; ------------------------
; this is the branch used to add normal non-control characters
; with ED-LOOP as the stacked return address.
; it is also the OUTPUT service routine for system channel 'R'.
;; ADD-CHAR
L0F81: RES 0,(IY+$07) ; set MODE to 'L'
X0F85: LD HL,($5C5B) ; fetch address of keyboard cursor from K_CUR
CALL L1652 ; routine ONE-SPACE creates one space.
; either a continuation of above or from ED-CONTR with ED-LOOP on stack.
;; ADD-CH-1
L0F8B: LD (DE),A ; load current character to last new location.
INC DE ; address next
LD ($5C5B),DE ; and update K_CUR system variable.
RET ; return - either a simple return
; from ADD-CHAR or to ED-LOOP on stack.
; ---
; a branch of the editing loop to deal with control characters
; using a look-up table.
;; ED-KEYS
L0F92: LD E,A ; character to E.
LD D,$00 ; prepare to add.
LD HL,L0FA0 - 7 ; base address of editing keys table. $0F99
ADD HL,DE ; add E
LD E,(HL) ; fetch offset to E
ADD HL,DE ; add offset for address of handling routine.
PUSH HL ; push the address on machine stack.
LD HL,($5C5B) ; load address of cursor from K_CUR.
RET ; an make an indirect jump forward to routine.
; ------------------
; Editing keys table
; ------------------
; For each code in the range $07 to $0F this table contains a
; single offset byte to the routine that services that code.
; Note. for what was intended there should also have been an
; entry for chr$ 6 with offset to ed-symbol.
;; ed-keys-t
L0FA0: DB L0FA9 - $ ; 07d offset $09 to Address: ED-EDIT
DB L1007 - $ ; 08d offset $66 to Address: ED-LEFT
DB L100C - $ ; 09d offset $6A to Address: ED-RIGHT
DB L0FF3 - $ ; 10d offset $50 to Address: ED-DOWN
DB L1059 - $ ; 11d offset $B5 to Address: ED-UP
DB L1015 - $ ; 12d offset $70 to Address: ED-DELETE
DB L1024 - $ ; 13d offset $7E to Address: ED-ENTER
DB L1076 - $ ; 14d offset $CF to Address: ED-SYMBOL
DB L107C - $ ; 15d offset $D4 to Address: ED-GRAPH
; ---------------
; Handle EDIT key
; ---------------
; The user has pressed SHIFT 1 to bring edit line down to bottom of screen.
; Alternatively the user wishes to clear the input buffer and start again.
; Alternatively ...
;; ED-EDIT
L0FA9: LD HL,($5C49) ; fetch E_PPC the last line number entered.
; Note. may not exist and may follow program.
BIT 5,(IY+$37) ; test FLAGX - input mode ?
JP NZ,L1097 ; jump forward to CLEAR-SP if not in editor.
CALL L196E ; routine LINE-ADDR to find address of line
; or following line if it doesn't exist.
CALL L1695 ; routine LINE-NO will get line number from
; address or previous line if at end-marker.
LD A,D ; if there is no program then DE will
OR E ; contain zero so test for this.
JP Z,L1097 ; jump to to CLEAR-SP if so.
; Note. at this point we have a validated line number, not just an
; approximation and it would be best to update E_PPC with the true
; cursor line value which would enable the line cursor to be suppressed
; in all situations - see shortly.
PUSH HL ; save address of line.
INC HL ; address low byte of length.
LD C,(HL) ; transfer to C
INC HL ; next to high byte
LD B,(HL) ; transfer to B.
LD HL,$000A ; an overhead of ten bytes
ADD HL,BC ; is added to length.
LD B,H ; transfer adjusted value
LD C,L ; to BC register.
CALL L1F05 ; routine TEST-ROOM checks free memory.
CALL L1097 ; routine CLEAR-SP clears editing area.
LD HL,($5C51) ; address CURCHL
EX (SP),HL ; swap with line address on stack
PUSH HL ; save line address underneath
LD A,$FF ; select system channel 'R'
CALL L1601 ; routine CHAN-OPEN opens it
POP HL ; drop line address
DEC HL ; make it point to first byte of line num.
DEC (IY+$0F) ; decrease E_PPC_lo to suppress line cursor.
; Note. ineffective when E_PPC is one
; greater than last line of program perhaps
; as a result of a delete.
; credit. Paul Harrison 1982.
CALL L1855 ; routine OUT-LINE outputs the BASIC line
; to the editing area.
INC (IY+$0F) ; restore E_PPC_lo to the previous value.
LD HL,($5C59) ; address E_LINE in editing area.
INC HL ; advance
INC HL ; past space
INC HL ; and digit characters
INC HL ; of line number.
LD ($5C5B),HL ; update K_CUR to address start of BASIC.
POP HL ; restore the address of CURCHL.
CALL L1615 ; routine CHAN-FLAG sets flags for it.
RET ; RETURN to ED-LOOP.
; -------------------
; Cursor down editing
; -------------------
; The BASIC lines are displayed at the top of the screen and the user
; wishes to move the cursor down one line in edit mode.
; In input mode this key can be used as an alternative to entering STOP.
;; ED-DOWN
L0FF3: BIT 5,(IY+$37) ; test FLAGX - Input Mode ?
JR NZ,L1001 ; skip to ED-STOP if so
LD HL,$5C49 ; address E_PPC - 'current line'
CALL L190F ; routine LN-FETCH fetches number of next
; line or same if at end of program.
JR L106E ; forward to ED-LIST to produce an
; automatic listing.
; ---
;; ED-STOP
L1001: LD (IY+$00),$10 ; set ERR_NR to 'STOP in INPUT' code
JR L1024 ; forward to ED-ENTER to produce error.
; -------------------
; Cursor left editing
; -------------------
; This acts on the cursor in the lower section of the screen in both
; editing and input mode.
;; ED-LEFT
L1007: CALL L1031 ; routine ED-EDGE moves left if possible
JR L1011 ; forward to ED-CUR to update K-CUR
; and return to ED-LOOP.
; --------------------
; Cursor right editing
; --------------------
; This acts on the cursor in the lower screen in both editing and input
; mode and moves it to the right.
;; ED-RIGHT
L100C: LD A,(HL) ; fetch addressed character.
CP $0D ; is it carriage return ?
RET Z ; return if so to ED-LOOP
INC HL ; address next character
;; ED-CUR
L1011: LD ($5C5B),HL ; update K_CUR system variable
RET ; return to ED-LOOP
; --------------
; DELETE editing
; --------------
; This acts on the lower screen and deletes the character to left of
; cursor. If control characters are present these are deleted first
; leaving the naked parameter (0-7) which appears as a '?' except in the
; case of chr$ 6 which is the comma control character. It is not mandatory
; to delete these second characters.
;; ED-DELETE
L1015: CALL L1031 ; routine ED-EDGE moves cursor to left.
LD BC,$0001 ; of character to be deleted.
JP L19E8 ; to RECLAIM-2 reclaim the character.
; ------------------------------------------
; Ignore next 2 codes from key-input routine
; ------------------------------------------
; Since AT and TAB cannot be entered this point is never reached
; from the keyboard. If inputting from a tape device or network then
; the control and two following characters are ignored and processing
; continues as if a carriage return had been received.
; Here, perhaps, another Spectrum has said print #15; AT 0,0; "This is yellow"
; and this one is interpreting input #15; a$.
;; ED-IGNORE
L101E: CALL L15D4 ; routine WAIT-KEY to ignore keystroke.
CALL L15D4 ; routine WAIT-KEY to ignore next key.
; -------------
; Enter/newline
; -------------
; The enter key has been pressed to have BASIC line or input accepted.
;; ED-ENTER
L1024: POP HL ; discard address ED-LOOP
POP HL ; drop address ED-ERROR
;; ED-END
L1026: POP HL ; the previous value of ERR_SP
LD ($5C3D),HL ; is restored to ERR_SP system variable
BIT 7,(IY+$00) ; is ERR_NR $FF (= 'OK') ?
RET NZ ; return if so
LD SP,HL ; else put error routine on stack
RET ; and make an indirect jump to it.
; -----------------------------
; Move cursor left when editing
; -----------------------------
; This routine moves the cursor left. The complication is that it must
; not position the cursor between control codes and their parameters.
; It is further complicated in that it deals with TAB and AT characters
; which are never present from the keyboard.
; The method is to advance from the beginning of the line each time,
; jumping one, two, or three characters as necessary saving the original
; position at each jump in DE. Once it arrives at the cursor then the next
; legitimate leftmost position is in DE.
;; ED-EDGE
L1031: SCF ; carry flag must be set to call the nested
CALL L1195 ; subroutine SET-DE.
; if input then DE=WORKSP
; if editing then DE=E_LINE
SBC HL,DE ; subtract address from start of line
ADD HL,DE ; and add back.
INC HL ; adjust for carry.
POP BC ; drop return address
RET C ; return to ED-LOOP if already at left
; of line.
PUSH BC ; resave return address - ED-LOOP.
LD B,H ; transfer HL - cursor address
LD C,L ; to BC register pair.
; at this point DE addresses start of line.
;; ED-EDGE-1
L103E: LD H,D ; transfer DE - leftmost pointer
LD L,E ; to HL
INC HL ; address next leftmost character to
; advance position each time.
LD A,(DE) ; pick up previous in A
AND $F0 ; lose the low bits
CP $10 ; is it INK to TAB $10-$1F ?
; that is, is it followed by a parameter ?
JR NZ,L1051 ; to ED-EDGE-2 if not
; HL has been incremented once
INC HL ; address next as at least one parameter.
; in fact since 'tab' and 'at' cannot be entered the next section seems
; superfluous.
; The test will always fail and the jump to ED-EDGE-2 will be taken.
LD A,(DE) ; reload leftmost character
SUB $17 ; decimal 23 ('tab')
ADC A,$00 ; will be 0 for 'tab' and 'at'.
JR NZ,L1051 ; forward to ED-EDGE-2 if not
; HL has been incremented twice
INC HL ; increment a third time for 'at'/'tab'
;; ED-EDGE-2
L1051: AND A ; prepare for true subtraction
SBC HL,BC ; subtract cursor address from pointer
ADD HL,BC ; and add back
; Note when HL matches the cursor position BC,
; there is no carry and the previous
; position is in DE.
EX DE,HL ; transfer result to DE if looping again.
; transfer DE to HL to be used as K-CUR
; if exiting loop.
JR C,L103E ; back to ED-EDGE-1 if cursor not matched.
RET ; return.
; -----------------
; Cursor up editing
; -----------------
; The main screen displays part of the BASIC program and the user wishes
; to move up one line scrolling if necessary.
; This has no alternative use in input mode.
;; ED-UP
L1059: BIT 5,(IY+$37) ; test FLAGX - input mode ?
RET NZ ; return if not in editor - to ED-LOOP.
LD HL,($5C49) ; get current line from E_PPC
CALL L196E ; routine LINE-ADDR gets address
EX DE,HL ; and previous in DE
CALL L1695 ; routine LINE-NO gets prev line number
LD HL,$5C4A ; set HL to E_PPC_hi as next routine stores
; top first.
CALL L191C ; routine LN-STORE loads DE value to HL
; high byte first - E_PPC_lo takes E
; this branch is also taken from ed-down.
;; ED-LIST
L106E: CALL L1795 ; routine AUTO-LIST lists to upper screen
; including adjusted current line.
LD A,$00 ; select lower screen again
JP L1601 ; exit via CHAN-OPEN to ED-LOOP
; --------------------------------
; Use of symbol and graphics codes
; --------------------------------
; These will not be encountered with the keyboard but would be handled
; otherwise as follows.
; As noted earlier, Vickers says there should have been an entry in
; the KEYS table for chr$ 6 which also pointed here.
; If, for simplicity, two Spectrums were both using #15 as a bi-directional
; channel connected to each other:-
; then when the other Spectrum has said PRINT #15; x, y
; input #15; i ; j would treat the comma control as a newline and the
; control would skip to input j.
; You can get round the missing chr$ 6 handler by sending multiple print
; items separated by a newline '.
; chr$14 would have the same functionality.
; This is chr$ 14.
;; ED-SYMBOL
L1076: BIT 7,(IY+$37) ; test FLAGX - is this INPUT LINE ?
JR Z,L1024 ; back to ED-ENTER if not to treat as if
; enter had been pressed.
; else continue and add code to buffer.
; Next is chr$ 15
; Note that ADD-CHAR precedes the table so we can't offset to it directly.
;; ED-GRAPH
L107C: JP L0F81 ; jump back to ADD-CHAR
; --------------------
; Editor error routine
; --------------------
; If an error occurs while editing, or inputting, then ERR_SP
; points to the stack location holding address ED_ERROR.
;; ED-ERROR
L107F: BIT 4,(IY+$30) ; test FLAGS2 - is K channel in use ?
JR Z,L1026 ; back to ED-END if not.
; but as long as we're editing lines or inputting from the keyboard, then
; we've run out of memory so give a short rasp.
LD (IY+$00),$FF ; reset ERR_NR to 'OK'.
LD D,$00 ; prepare for beeper.
LD E,(IY-$02) ; use RASP value.
LD HL,$1A90 ; set a duration.
CALL L03B5 ; routine BEEPER emits a warning rasp.
JP L0F30 ; to ED-AGAIN to re-stack address of
; this routine and make ERR_SP point to it.
; ---------------------
; Clear edit/work space
; ---------------------
; The editing area or workspace is cleared depending on context.
; This is called from ED-EDIT to clear workspace if edit key is
; used during input, to clear editing area if no program exists
; and to clear editing area prior to copying the edit line to it.
; It is also used by the error routine to clear the respective
; area depending on FLAGX.
;; CLEAR-SP
L1097: PUSH HL ; preserve HL
CALL L1190 ; routine SET-HL
; if in edit HL = WORKSP-1, DE = E_LINE
; if in input HL = STKBOT, DE = WORKSP
DEC HL ; adjust
CALL L19E5 ; routine RECLAIM-1 reclaims space
LD ($5C5B),HL ; set K_CUR to start of empty area
LD (IY+$07),$00 ; set MODE to 'KLC'
POP HL ; restore HL.
RET ; return.
; ---------------------
; Handle keyboard input
; ---------------------
; This is the service routine for the input stream of the keyboard
; channel 'K'.
;; KEY-INPUT
L10A8: BIT 3,(IY+$02) ; test TV_FLAG - has a key been pressed in
; editor ?
CALL NZ,L111D ; routine ED-COPY if so to reprint the lower
; screen at every keystroke.
AND A ; clear carry - required exit condition.
BIT 5,(IY+$01) ; test FLAGS - has a new key been pressed ?
RET Z ; return if not.
LD A,($5C08) ; system variable LASTK will hold last key -
; from the interrupt routine.
RES 5,(IY+$01) ; update FLAGS - reset the new key flag.
PUSH AF ; save the input character.
BIT 5,(IY+$02) ; test TV_FLAG - clear lower screen ?
CALL NZ,L0D6E ; routine CLS-LOWER if so.
POP AF ; restore the character code.
CP $20 ; if space or higher then
JR NC,L111B ; forward to KEY-DONE2 and return with carry
; set to signal key-found.
CP $10 ; with 16d INK and higher skip
JR NC,L10FA ; forward to KEY-CONTR.
CP $06 ; for 6 - 15d
JR NC,L10DB ; skip forward to KEY-M-CL to handle Modes
; and CapsLock.
; that only leaves 0-5, the flash bright inverse switches.
LD B,A ; save character in B
AND $01 ; isolate the embedded parameter (0/1).
LD C,A ; and store in C
LD A,B ; re-fetch copy (0-5)
RRA ; halve it 0, 1 or 2.
ADD A,$12 ; add 18d gives 'flash', 'bright'
; and 'inverse'.
JR L1105 ; forward to KEY-DATA with the
; parameter (0/1) in C.
; ---
; Now separate capslock 06 from modes 7-15.
;; KEY-M-CL
L10DB: JR NZ,L10E6 ; forward to KEY-MODE if not 06 (capslock)
LD HL,$5C6A ; point to FLAGS2
LD A,$08 ; value 00000100
XOR (HL) ; toggle BIT 2 of FLAGS2 the capslock bit
LD (HL),A ; and store result in FLAGS2 again.
JR L10F4 ; forward to KEY-FLAG to signal no-key.
; ---
;; KEY-MODE
L10E6: CP $0E ; compare with chr 14d
RET C ; return with carry set "key found" for
; codes 7 - 13d leaving 14d and 15d
; which are converted to mode codes.
SUB $0D ; subtract 13d leaving 1 and 2
; 1 is 'E' mode, 2 is 'G' mode.
LD HL,$5C41 ; address the MODE system variable.
CP (HL) ; compare with existing value before
LD (HL),A ; inserting the new value.
JR NZ,L10F4 ; forward to KEY-FLAG if it has changed.
LD (HL),$00 ; else make MODE zero - KLC mode
; Note. while in Extended/Graphics mode,
; the Extended Mode/Graphics key is pressed
; again to get out.
;; KEY-FLAG
L10F4: SET 3,(IY+$02) ; update TV_FLAG - show key state has changed
CP A ; clear carry and reset zero flags -
; no actual key returned.
RET ; make the return.
; ---
; now deal with colour controls - 16-23 ink, 24-31 paper
;; KEY-CONTR
L10FA: LD B,A ; make a copy of character.
AND $07 ; mask to leave bits 0-7
LD C,A ; and store in C.
LD A,$10 ; initialize to 16d - INK.
BIT 3,B ; was it paper ?
JR NZ,L1105 ; forward to KEY-DATA with INK 16d and
; colour in C.
INC A ; else change from INK to PAPER (17d) if so.
;; KEY-DATA
L1105: LD (IY-$2D),C ; put the colour (0-7)/state(0/1) in KDATA
LD DE,L110D ; address: KEY-NEXT will be next input stream
JR L1113 ; forward to KEY-CHAN to change it ...
; ---
; ... so that INPUT_AD directs control to here at next call to WAIT-KEY
;; KEY-NEXT
L110D: LD A,($5C0D) ; pick up the parameter stored in KDATA.
LD DE,L10A8 ; address: KEY-INPUT will be next input stream
; continue to restore default channel and
; make a return with the control code.
;; KEY-CHAN
L1113: LD HL,($5C4F) ; address start of CHANNELS area using CHANS
; system variable.
; Note. One might have expected CURCHL to
; have been used.
INC HL ; step over the
INC HL ; output address
LD (HL),E ; and update the input
INC HL ; routine address for
LD (HL),D ; the next call to WAIT-KEY.
;; KEY-DONE2
L111B: SCF ; set carry flag to show a key has been found
RET ; and return.
; --------------------
; Lower screen copying
; --------------------
; This subroutine is called whenever the line in the editing area or
; input workspace is required to be printed to the lower screen.
; It is by calling this routine after any change that the cursor, for
; instance, appears to move to the left.
; Remember the edit line will contain characters and tokens
; e.g. "1000 LET a = 1" is 12 characters.
;; ED-COPY
L111D: CALL L0D4D ; routine TEMPS sets temporary attributes.
RES 3,(IY+$02) ; update TV_FLAG - signal no change in mode
RES 5,(IY+$02) ; update TV_FLAG - signal don't clear lower
; screen.
LD HL,($5C8A) ; fetch SPOSNL
PUSH HL ; and save on stack.
LD HL,($5C3D) ; fetch ERR_SP
PUSH HL ; and save also
LD HL,L1167 ; address: ED-FULL
PUSH HL ; is pushed as the error routine
LD ($5C3D),SP ; and ERR_SP made to point to it.
LD HL,($5C82) ; fetch ECHO_E
PUSH HL ; and push also
SCF ; set carry flag to control SET-DE
CALL L1195 ; call routine SET-DE
; if in input DE = WORKSP
; if in edit DE = E_LINE
EX DE,HL ; start address to HL
CALL L187D ; routine OUT-LINE2 outputs entire line up to
; carriage return including initial
; characterized line number when present.
EX DE,HL ; transfer new address to DE
CALL L18E1 ; routine OUT-CURS considers a
; terminating cursor.
LD HL,($5C8A) ; fetch updated SPOSNL
EX (SP),HL ; exchange with ECHO_E on stack
EX DE,HL ; transfer ECHO_E to DE
CALL L0D4D ; routine TEMPS to re-set attributes
; if altered.
; the lower screen was not cleared, at the outset, so if deleting then old
; text from a previous print may follow this line and requires blanking.
;; ED-BLANK
L1150: LD A,($5C8B) ; fetch SPOSNL_hi is current line
SUB D ; compare with old
JR C,L117C ; forward to ED-C-DONE if no blanking
JR NZ,L115E ; forward to ED-SPACES if line has changed
LD A,E ; old column to A
SUB (IY+$50) ; subtract new in SPOSNL_lo
JR NC,L117C ; forward to ED-C-DONE if no backfilling.
;; ED-SPACES
L115E: LD A,$20 ; prepare a space.
PUSH DE ; save old line/column.
CALL L09F4 ; routine PRINT-OUT prints a space over
; any text from previous print.
; Note. Since the blanking only occurs when
; using $09F4 to print to the lower screen,
; there is no need to vector via a RST 10
; and we can use this alternate set.
POP DE ; restore the old line column.
JR L1150 ; back to ED-BLANK until all old text blanked.
; -------
; ED-FULL
; -------
; this is the error routine addressed by ERR_SP. This is not for the out of
; memory situation as we're just printing. The pitch and duration are exactly
; the same as used by ED-ERROR from which this has been augmented. The
; situation is that the lower screen is full and a rasp is given to suggest
; that this is perhaps not the best idea you've had that day.
;; ED-FULL
L1167: LD D,$00 ; prepare to moan.
LD E,(IY-$02) ; fetch RASP value.
LD HL,$1A90 ; set duration.
CALL L03B5 ; routine BEEPER.
LD (IY+$00),$FF ; clear ERR_NR.
LD DE,($5C8A) ; fetch SPOSNL.
JR L117E ; forward to ED-C-END
; -------
; the exit point from line printing continues here.
;; ED-C-DONE
L117C: POP DE ; fetch new line/column.
POP HL ; fetch the error address.
; the error path rejoins here.
;; ED-C-END
L117E: POP HL ; restore the old value of ERR_SP.
LD ($5C3D),HL ; update the system variable ERR_SP
POP BC ; old value of SPOSN_L
PUSH DE ; save new value
CALL L0DD9 ; routine CL-SET and PO-STORE
; update ECHO_E and SPOSN_L from BC
POP HL ; restore new value
LD ($5C82),HL ; and update ECHO_E
LD (IY+$26),$00 ; make error pointer X_PTR_hi out of bounds
RET ; return
; -----------------------------------------------
; Point to first and last locations of work space
; -----------------------------------------------
; These two nested routines ensure that the appropriate pointers are
; selected for the editing area or workspace. The routines that call
; these routines are designed to work on either area.
; this routine is called once
;; SET-HL
L1190: LD HL,($5C61) ; fetch WORKSP to HL.
DEC HL ; point to last location of editing area.
AND A ; clear carry to limit exit points to first
; or last.
; this routine is called with carry set and exits at a conditional return.
;; SET-DE
L1195: LD DE,($5C59) ; fetch E_LINE to DE
BIT 5,(IY+$37) ; test FLAGX - Input Mode ?
RET Z ; return now if in editing mode
LD DE,($5C61) ; fetch WORKSP to DE
RET C ; return if carry set ( entry = set-de)
LD HL,($5C63) ; fetch STKBOT to HL as well
RET ; and return (entry = set-hl (in input))
; -------------------------------
; Remove floating point from line
; -------------------------------
; When a BASIC LINE or the INPUT BUFFER is parsed any numbers will have
; an invisible chr 14d inserted after them and the 5-byte integer or
; floating point form inserted after that. Similar invisible value holders
; are also created after the numeric and string variables in a DEF FN list.
; This routine removes these 'compiled' numbers from the edit line or
; input workspace.
;; REMOVE-FP
L11A7: LD A,(HL) ; fetch character
CP $0E ; is it the number marker ?
LD BC,$0006 ; prepare for six bytes
CALL Z,L19E8 ; routine RECLAIM-2 reclaims space if $0E
LD A,(HL) ; reload next (or same) character
INC HL ; and advance address
CP $0D ; end of line or input buffer ?
JR NZ,L11A7 ; back to REMOVE-FP until entire line done.
RET ; return
;*********************************
;** Part 6. EXECUTIVE ROUTINES **
;*********************************
; The memory.
;
; +---------+-----------+------------+--------------+-------------+--
; | BASIC | Display | Attributes | ZX Printer | System |
; | ROM | File | File | Buffer | Variables |
; +---------+-----------+------------+--------------+-------------+--
; ^ ^ ^ ^ ^ ^
; $0000 $4000 $5800 $5B00 $5C00 $5CB6 = CHANS
;
;
; --+----------+---+---------+-----------+---+------------+--+---+--
; | Channel |$80| BASIC | Variables |$80| Edit Line |NL|$80|
; | Info | | Program | Area | | or Command | | |
; --+----------+---+---------+-----------+---+------------+--+---+--
; ^ ^ ^ ^ ^
; CHANS PROG VARS E_LINE WORKSP
;
;
; ---5--> <---2--- <--3---
; --+-------+--+------------+-------+-------+---------+-------+-+---+------+
; | INPUT |NL| Temporary | Calc. | Spare | Machine | GOSUB |?|$3E| UDGs |
; | data | | Work Space | Stack | | Stack | Stack | | | |
; --+-------+--+------------+-------+-------+---------+-------+-+---+------+
; ^ ^ ^ ^ ^ ^ ^
; WORKSP STKBOT STKEND sp RAMTOP UDG P_RAMT
;
; -------------------
; Handle NEW command
; -------------------
; The NEW command is about to set all RAM below RAMTOP to zero and
; then re-initialize the system. All RAM above RAMTOP should, and will be,
; preserved.
; There is nowhere to store values in RAM or on the stack which becomes
; inoperable. Similarly PUSH and CALL instructions cannot be used to
; store values or section common code. The alternate register set is the only
; place available to store 3 persistent 16-bit system variables.
;; NEW
L11B7: DI ; disable interrupts - machine stack will be
; cleared.
LD A,$FF ; flag coming from NEW.
LD DE,($5CB2) ; fetch RAMTOP as top value.
EXX ; switch in alternate set.
LD BC,($5CB4) ; fetch P-RAMT differs on 16K/48K machines.
LD DE,($5C38) ; fetch RASP/PIP.
LD HL,($5C7B) ; fetch UDG differs on 16K/48K machines.
EXX ; switch back to main set and continue into...
; ---------------------------
; Main entry (initialization)
; ---------------------------
; This common code tests ram and sets it to zero re-initializing
; all the non-zero system variables and channel information.
; The A register tells if coming from START or NEW
;; START-NEW
L11CB: LD B,A ; save the flag for later branching.
LD A,$07 ; select a white border
OUT ($FE),A ; and set it now.
LD A,$3F ; load accumulator with last page in ROM.
LD I,A ; set the I register - this remains constant
; and can't be in range $40 - $7F as 'snow'
; appears on the screen.
NOP ; these seem unnecessary.
NOP ;
NOP ;
NOP ;
; NOP ;
; NOP ;
RST 8
DB _TAPE_INIT
; ------------
; Check RAM
; ------------
; Typically a Spectrum will have 16K or 48K of Ram and this code will
; test it all till it finds an unpopulated location or, less likely, a
; faulty location. Usually it stops when it reaches the top $FFFF or
; in the case of NEW the supplied top value. The entire screen turns
; black with sometimes red stripes on black paper visible.
;; ram-check
L11DA: LD H,D ; transfer the top value to
LD L,E ; the HL register pair.
;; RAM-FILL
L11DC: LD (HL),$02 ; load with 2 - red ink on black paper
DEC HL ; next lower
CP H ; have we reached ROM - $3F ?
JR NZ,L11DC ; back to RAM-FILL if not.
;; RAM-READ
L11E2: AND A ; clear carry - prepare to subtract
SBC HL,DE ; subtract and add back setting
ADD HL,DE ; carry when back at start.
INC HL ; and increment for next iteration.
JR NC,L11EF ; forward to RAM-DONE if we've got back to
; starting point with no errors.
DEC (HL) ; decrement to 1.
JR Z,L11EF ; forward to RAM-DONE if faulty.
DEC (HL) ; decrement to zero.
JR Z,L11E2 ; back to RAM-READ if zero flag was set.
;; RAM-DONE
L11EF: DEC HL ; step back to last valid location.
EXX ; regardless of state, set up possibly
; stored system variables in case from NEW.
LD ($5CB4),BC ; insert P-RAMT.
LD ($5C38),DE ; insert RASP/PIP.
LD ($5C7B),HL ; insert UDG.
EXX ; switch in main set.
INC B ; now test if we arrived here from NEW.
JR Z,L1219 ; forward to RAM-SET if we did.
; this section applies to START only.
LD ($5CB4),HL ; set P-RAMT to the highest working RAM
; address.
LD DE,$3EAF ; address of last byte of 'U' bitmap in ROM.
LD BC,$00A8 ; there are 21 user defined graphics.
EX DE,HL ; switch pointers and make the UDGs a
LDDR ; copy of the standard characters A - U.
EX DE,HL ; switch the pointer to HL.
INC HL ; update to start of 'A' in RAM.
LD ($5C7B),HL ; make UDG system variable address the first
; bitmap.
DEC HL ; point at RAMTOP again.
LD BC,$0040 ; set the values of
LD ($5C38),BC ; the PIP and RASP system variables.
; the NEW command path rejoins here.
;; RAM-SET
L1219: LD ($5CB2),HL ; set system variable RAMTOP to HL.
LD HL,CHARS-0X100 ;$3C00 ; a strange place to set the pointer to the
LD ($5C36),HL ; character set, CHARS - as no printing yet.
LD HL,($5CB2) ; fetch RAMTOP to HL again as we've lost it.
LD (HL),$3E ; top of user ram holds GOSUB end marker
; an impossible line number - see RETURN.
; no significance in the number $3E. It has
; been traditional since the ZX80.
DEC HL ; followed by empty byte (not important).
LD SP,HL ; set up the machine stack pointer.
DEC HL ;
DEC HL ;
LD ($5C3D),HL ; ERR_SP is where the error pointer is
; at moment empty - will take address MAIN-4
; at the call preceding that address,
; although interrupts and calls will make use
; of this location in meantime.
IM 1 ; select interrupt mode 1.
LD IY,$5C3A ; set IY to ERR_NR. IY can reach all standard
; system variables but shadow ROM system
; variables will be mostly out of range.
EI ; enable interrupts now that we have a stack.
LD HL,$5CB6 ; the address of the channels - initially
; following system variables.
LD ($5C4F),HL ; set the CHANS system variable.
LD DE,L15AF ; address: init-chan in ROM.
LD BC,$0015 ; there are 21 bytes of initial data in ROM.
EX DE,HL ; swap the pointers.
LDIR ; copy the bytes to RAM.
EX DE,HL ; swap pointers. HL points to program area.
DEC HL ; decrement address.
LD ($5C57),HL ; set DATADD to location before program area.
INC HL ; increment again.
LD ($5C53),HL ; set PROG the location where BASIC starts.
LD ($5C4B),HL ; set VARS to same location with a
LD (HL),$80 ; variables end-marker.
INC HL ; advance address.
LD ($5C59),HL ; set E_LINE, where the edit line
; will be created.
; Note. it is not strictly necessary to
; execute the next fifteen bytes of code
; as this will be done by the call to SET-MIN.
; --
LD (HL),$0D ; initially just has a carriage return
INC HL ; followed by
LD (HL),$80 ; an end-marker.
INC HL ; address the next location.
LD ($5C61),HL ; set WORKSP - empty workspace.
LD ($5C63),HL ; set STKBOT - bottom of the empty stack.
LD ($5C65),HL ; set STKEND to the end of the empty stack.
; --
LD A,$38 ; the colour system is set to white paper,
; black ink, no flash or bright.
LD ($5C8D),A ; set ATTR_P permanent colour attributes.
LD ($5C8F),A ; set ATTR_T temporary colour attributes.
LD ($5C48),A ; set BORDCR the border colour/lower screen
; attributes.
LD HL,$0523 ; The keyboard repeat and delay values
LD ($5C09),HL ; are loaded to REPDEL and REPPER.
DEC (IY-$3A) ; set KSTATE-0 to $FF.
DEC (IY-$36) ; set KSTATE-4 to $FF.
; thereby marking both available.
LD HL,L15C6 ; set source to ROM Address: init-strm
LD DE,$5C10 ; set destination to system variable STRMS-FD
LD BC,$000E ; copy the 14 bytes of initial 7 streams data
LDIR ; from ROM to RAM.
SET 1,(IY+$01) ; update FLAGS - signal printer in use.
;===============================
CALL PRINTER_INITER
; CALL L0EDF ; call routine CLEAR-PRB to initialize system
; variables associated with printer.
;===============================
LD (IY+$31),$02 ; set DF_SZ the lower screen display size to
; two lines
CALL L0D6B ; call routine CLS to set up system
; variables associated with screen and clear
; the screen and set attributes.
XOR A ; clear accumulator so that we can address
LD DE,L1539 - 1 ; the message table directly.
CALL L0C0A ; routine PO-MSG puts
; '(c) 1982 Sinclair Research Ltd'
; at bottom of display.
SET 5,(IY+$02) ; update TV_FLAG - signal lower screen will
; require clearing.
JR L12A9 ; forward to MAIN-1
; -------------------
; Main execution loop
; -------------------
;
;
;; MAIN-EXEC
L12A2: LD (IY+$31),$02 ; set DF_SZ lower screen display file
; size to 2 lines.
CALL L1795 ; routine AUTO-LIST
;; MAIN-1
L12A9: CALL L16B0 ; routine SET-MIN clears work areas.
;; MAIN-2
L12AC: LD A,$00 ; select channel 'K' the keyboard
CALL L1601 ; routine CHAN-OPEN opens it
CALL L0F2C ; routine EDITOR is called.
; Note the above routine is where the Spectrum
; waits for user-interaction. Perhaps the
; most common input at this stage
; is LOAD "".
CALL L1B17 ; routine LINE-SCAN scans the input.
BIT 7,(IY+$00) ; test ERR_NR - will be $FF if syntax
; is correct.
JR NZ,L12CF ; forward, if correct, to MAIN-3.
;
BIT 4,(IY+$30) ; test FLAGS2 - K channel in use ?
JR Z,L1303 ; forward to MAIN-4 if not.
;
LD HL,($5C59) ; an editing error so address E_LINE.
CALL L11A7 ; routine REMOVE-FP removes the hidden
; floating-point forms.
LD (IY+$00),$FF ; system variable ERR_NR is reset to 'OK'.
JR L12AC ; back to MAIN-2 to allow user to correct.
; ---
; the branch was here if syntax has passed test.
;; MAIN-3
L12CF: LD HL,($5C59) ; fetch the edit line address from E_LINE.
LD ($5C5D),HL ; system variable CH_ADD is set to first
; character of edit line.
; Note. the above two instructions are a little
; inadequate.
; They are repeated with a subtle difference
; at the start of the next subroutine and are
; therefore not required above.
CALL L19FB ; routine E-LINE-NO will fetch any line
; number to BC if this is a program line.
LD A,B ; test if the number of
OR C ; the line is non-zero.
JP NZ,L155D ; jump forward to MAIN-ADD if so to add the
; line to the BASIC program.
; Has the user just pressed the ENTER key ?
RST 18H ; GET-CHAR gets character addressed by CH_ADD.
CP $0D ; is it a carriage return ?
JR Z,L12A2 ; back to MAIN-EXEC if so for an automatic
; listing.
; this must be a direct command.
BIT 0,(IY+$30) ; test FLAGS2 - clear the main screen ?
CALL NZ,L0DAF ; routine CL-ALL, if so, e.g. after listing.
CALL L0D6E ; routine CLS-LOWER anyway.
LD A,$19 ; compute scroll count to 25 minus
SUB (IY+$4F) ; value of S_POSN_hi.
LD ($5C8C),A ; update SCR_CT system variable.
SET 7,(IY+$01) ; update FLAGS - signal running program.
LD (IY+$00),$FF ; set ERR_NR to 'OK'.
LD (IY+$0A),$01 ; set NSPPC to one for first statement.
CALL L1B8A ; call routine LINE-RUN to run the line.
; sysvar ERR_SP therefore addresses MAIN-4
; Examples of direct commands are RUN, CLS, LOAD "", PRINT USR 40000,
; LPRINT "A"; etc..
; If a user written machine-code program disables interrupts then it
; must enable them to pass the next step. We also jumped to here if the
; keyboard was not being used.
;; MAIN-4
L1303: HALT ; wait for interrupt.
RES 5,(IY+$01) ; update FLAGS - signal no new key.
BIT 1,(IY+$30) ; test FLAGS2 - is printer buffer clear ?
CALL NZ,L0ECD ; call routine COPY-BUFF if not.
; Note. the programmer has neglected
; to set bit 1 of FLAGS first.
LD A,($5C3A) ; fetch ERR_NR
INC A ; increment to give true code.
; Now deal with a runtime error as opposed to an editing error.
; However if the error code is now zero then the OK message will be printed.
;; MAIN-G
L1313: PUSH AF ; save the error number.
LD HL,$0000 ; prepare to clear some system variables.
LD (IY+$37),H ; clear all the bits of FLAGX.
LD (IY+$26),H ; blank X_PTR_hi to suppress error marker.
LD ($5C0B),HL ; blank DEFADD to signal that no defined
; function is currently being evaluated.
LD HL,$0001 ; explicit - inc hl would do.
LD ($5C16),HL ; ensure STRMS-00 is keyboard.
CALL L16B0 ; routine SET-MIN clears workspace etc.
RES 5,(IY+$37) ; update FLAGX - signal in EDIT not INPUT mode.
; Note. all the bits were reset earlier.
CALL L0D6E ; call routine CLS-LOWER.
SET 5,(IY+$02) ; update TV_FLAG - signal lower screen
; requires clearing.
POP AF ; bring back the error number
LD B,A ; and make a copy in B.
CP $0A ; is it a print-ready digit ?
JR C,L133C ; forward to MAIN-5 if so.
ADD A,$07 ; add ASCII offset to letters.
;; MAIN-5
L133C: CALL L15EF ; call routine OUT-CODE to print the code.
LD A,$20 ; followed by a space.
RST 10H ; PRINT-A
LD A,B ; fetch stored report code.
LD DE,L1391 ; address: rpt-mesgs.
CALL L0C0A ; call routine PO-MSG to print.
X1349
IF BAS48_ONLY=1
XOR A
LD DE,L1536
ELSE
CALL L3B3B ; Spectrum 128 patch
NOP
ENDIF
L134D: CALL L0C0A ; routine PO-MSG prints them although it would
; be more succinct to use RST $10.
LD BC,($5C45) ; fetch PPC the current line number.
CALL L1A1B ; routine OUT-NUM-1 will print that
LD A,$3A ; then a ':'.
RST 10H ; PRINT-A
LD C,(IY+$0D) ; then SUBPPC for statement
LD B,$00 ; limited to 127
CALL L1A1B ; routine OUT-NUM-1
CALL L1097 ; routine CLEAR-SP clears editing area.
; which probably contained 'RUN'.
LD A,($5C3A) ; fetch ERR_NR again
INC A ; test for no error originally $FF.
JR Z,L1386 ; forward to MAIN-9 if no error.
CP $09 ; is code Report 9 STOP ?
JR Z,L1373 ; forward to MAIN-6 if so
CP $15 ; is code Report L Break ?
JR NZ,L1376 ; forward to MAIN-7 if not
; Stop or Break was encountered so consider CONTINUE.
;; MAIN-6
L1373: INC (IY+$0D) ; increment SUBPPC to next statement.
;; MAIN-7
L1376: LD BC,$0003 ; prepare to copy 3 system variables to
LD DE,$5C70 ; address OSPPC - statement for CONTINUE.
; also updating OLDPPC line number below.
LD HL,$5C44 ; set source top to NSPPC next statement.
BIT 7,(HL) ; did BREAK occur before the jump ?
; e.g. between GO TO and next statement.
JR Z,L1384 ; skip forward to MAIN-8, if not, as setup
; is correct.
ADD HL,BC ; set source to SUBPPC number of current
; statement/line which will be repeated.
;; MAIN-8
L1384: LDDR ; copy PPC to OLDPPC and SUBPPC to OSPCC
; or NSPPC to OLDPPC and NEWPPC to OSPCC
;; MAIN-9
L1386: LD (IY+$0A),$FF ; update NSPPC - signal 'no jump'.
RES 3,(IY+$01) ; update FLAGS - signal use 'K' mode for
; the first character in the editor and
JP L12AC ; jump back to MAIN-2.
; ----------------------
; Canned report messages
; ----------------------
; The Error reports with the last byte inverted. The first entry
; is a dummy entry. The last, which begins with $7F, the Spectrum
; character for copyright symbol, is placed here for convenience
; as is the preceding comma and space.
; The report line must accommodate a 4-digit line number and a 3-digit
; statement number which limits the length of the message text to twenty
; characters.
; e.g. "B Integer out of range, 1000:127"
;; rpt-mesgs
L1391 DB $80
DC "OK" ;DB 'O','K'+$80 ; 0
DC "NEXT without FOR" ;DEFM "NEXT without FO"
;DB 'R'+$80 ; 1
DC "Variable not found" ;DEFM "Variable not foun"
;DB 'd'+$80 ; 2
DC "Subscript wrong" ;DEFM "Subscript wron"
;DB 'g'+$80 ; 3
DC "Out of memory" ;DEFM "Out of memor"
;DB 'y'+$80 ; 4
DC "Out of screen" ;DEFM "Out of scree"
;DB 'n'+$80 ; 5
DC "Number too big" ;DEFM "Number too bi"
;DB 'g'+$80 ; 6
DC "RETURN without GOSUB" ;DEFM "RETURN without GOSU"
;DB 'B'+$80 ; 7
DC "End of file" ;DEFM "End of fil"
;DB 'e'+$80 ; 8
DC "STOP statement" ;DEFM "STOP statemen"
;DB 't'+$80 ; 9
DC "Invalid argument" ;DEFM "Invalid argumen"
;DB 't'+$80 ; A
DC "Integer out of range" ;DEFM "Integer out of rang"
;DB 'e'+$80 ; B
DC "Nonsense in BASIC" ;DEFM "Nonsense in BASI"
;DB 'C'+$80 ; C
DC "BREAK - CONT repeats" ;DEFM "BREAK - CONT repeat"
;DB 's'+$80 ; D
DC "Out of DATA" ;DEFM "Out of DAT"
;DB 'A'+$80 ; E
DC "Invalid file name" ;DEFM "Invalid file nam"
;DB 'e'+$80 ; F
DC "No room for line" ;DEFM "No room for lin"
;DB 'e'+$80 ; G
DC "STOP in INPUT" ;DEFM "STOP in INPU"
;DB 'T'+$80 ; H
DC "FOR without NEXT" ;DEFM "FOR without NEX"
;DB 'T'+$80 ; I
DC "Invalid I/O device" ;DEFM "Invalid I/O devic"
;DB 'e'+$80 ; J
DC "Invalid colour" ;DEFM "Invalid colou"
;DB 'r'+$80 ; K
DC "BREAK into program" ;DEFM "BREAK into progra"
;DB 'm'+$80 ; L
DC "RAMTOP no good" ;DEFM "RAMTOP no goo"
;DB 'd'+$80 ; M
DC "Statement lost" ;DEFM "Statement los"
;DB 't'+$80 ; N
DC "Invalid stream" ;DEFM "Invalid strea"
;DB 'm'+$80 ; O
DC "FN without DEF" ;DEFM "FN without DE"
;DB 'F'+$80 ; P
DC "Parameter error" ;DEFM "Parameter erro"
;DB 'r'+$80 ; Q
DC "Tape loading error" ;DEFM "Tape loading erro"
;DB 'r'+$80 ; R
L1536 EQU $-1
;; comma-sp
L1537 DC ", " ;DB ',',' '+$80 ; used in report line.
;; copyright
L1539 DB $7F ; copyright
DC " 1982 Sinclair Research Ltd" ;DEFM " 1982 Sinclair Research Lt"
;DB 'd'+$80
; -------------
; REPORT-G
; -------------
; Note ERR_SP points here during line entry which allows the
; normal 'Out of Memory' report to be augmented to the more
; precise 'No Room for line' report.
;; REPORT-G
; No Room for line
L1555: LD A,$10 ; i.e. 'G' -$30 -$07
LD BC,$0000 ; this seems unnecessary.
JP L1313 ; jump back to MAIN-G
; -----------------------------
; Handle addition of BASIC line
; -----------------------------
; Note this is not a subroutine but a branch of the main execution loop.
; System variable ERR_SP still points to editing error handler.
; A new line is added to the BASIC program at the appropriate place.
; An existing line with same number is deleted first.
; Entering an existing line number deletes that line.
; Entering a non-existent line allows the subsequent line to be edited next.
;; MAIN-ADD
L155D: LD ($5C49),BC ; set E_PPC to extracted line number.
LD HL,($5C5D) ; fetch CH_ADD - points to location after the
; initial digits (set in E_LINE_NO).
EX DE,HL ; save start of BASIC in DE.
LD HL,L1555 ; Address: REPORT-G
PUSH HL ; is pushed on stack and addressed by ERR_SP.
; the only error that can occur is
; 'Out of memory'.
LD HL,($5C61) ; fetch WORKSP - end of line.
SCF ; prepare for true subtraction.
SBC HL,DE ; find length of BASIC and
PUSH HL ; save it on stack.
LD H,B ; transfer line number
LD L,C ; to HL register.
CALL L196E ; routine LINE-ADDR will see if
; a line with the same number exists.
JR NZ,L157D ; forward if no existing line to MAIN-ADD1.
CALL L19B8 ; routine NEXT-ONE finds the existing line.
CALL L19E8 ; routine RECLAIM-2 reclaims it.
;; MAIN-ADD1
L157D: POP BC ; retrieve the length of the new line.
LD A,C ; and test if carriage return only
DEC A ; i.e. one byte long.
OR B ; result would be zero.
JR Z,L15AB ; forward to MAIN-ADD2 is so.
PUSH BC ; save the length again.
INC BC ; adjust for inclusion
INC BC ; of line number (two bytes)
INC BC ; and line length
INC BC ; (two bytes).
DEC HL ; HL points to location before the destination
LD DE,($5C53) ; fetch the address of PROG
PUSH DE ; and save it on the stack
CALL L1655 ; routine MAKE-ROOM creates BC spaces in
; program area and updates pointers.
POP HL ; restore old program pointer.
LD ($5C53),HL ; and put back in PROG as it may have been
; altered by the POINTERS routine.
POP BC ; retrieve BASIC length
PUSH BC ; and save again.
INC DE ; points to end of new area.
LD HL,($5C61) ; set HL to WORKSP - location after edit line.
DEC HL ; decrement to address end marker.
DEC HL ; decrement to address carriage return.
LDDR ; copy the BASIC line back to initial command.
LD HL,($5C49) ; fetch E_PPC - line number.
EX DE,HL ; swap it to DE, HL points to last of
; four locations.
POP BC ; retrieve length of line.
LD (HL),B ; high byte last.
DEC HL ;
LD (HL),C ; then low byte of length.
DEC HL ;
LD (HL),E ; then low byte of line number.
DEC HL ;
LD (HL),D ; then high byte range $0 - $27 (1-9999).
;; MAIN-ADD2
L15AB: POP AF ; drop the address of Report G
JP L12A2 ; and back to MAIN-EXEC producing a listing
; and to reset ERR_SP in EDITOR.
; ---------------------------
; Initial channel information
; ---------------------------
; This initial channel information is copied from ROM to RAM,
; during initialization. It's new location is after the system
; variables and is addressed by the system variable CHANS
; which means that it can slide up and down in memory.
; The table is never searched and the last character which could be anything
; other than a comma provides a convenient resting place for DATADD.
;; init-chan
L15AF DW L09F4 ; PRINT-OUT
DW L10A8 ; KEY-INPUT
DB "K"
DW L09F4 ; PRINT-OUT
DW L15C4 ; REPORT-J
DB "S"
DW L0F81 ; ADD-CHAR
DW L15C4 ; REPORT-J
DB "R"
;=======================================
DW PRN_TOKEN
; DW L09F4 ; PRINT-OUT
;=======================================
DW L15C4 ; REPORT-J
DB "P"
DB $80 ; End Marker
;; REPORT-J
L15C4: RST 08H ; ERROR-1
DB $12 ; Error Report: Invalid I/O device
; -------------------
; Initial stream data
; -------------------
; This is the initial stream data for the seven streams $FD - $03 that is
; copied from ROM to the STRMS system variables area during initialization.
; There are reserved locations there for another 12 streams.
; Each location contains an offset to the second byte of a channel.
; The first byte of a channel can't be used as that would result in an
; offset of zero for some and zero is used to denote that a stream is closed.
;; init-strm
L15C6: DB $01, $00 ; stream $FD offset to channel 'K'
DB $06, $00 ; stream $FE offset to channel 'S'
DB $0B, $00 ; stream $FF offset to channel 'R'
DB $01, $00 ; stream $00 offset to channel 'K'
DB $01, $00 ; stream $01 offset to channel 'K'
DB $06, $00 ; stream $02 offset to channel 'S'
DB $10, $00 ; stream $03 offset to channel 'P'
; ----------------------------
; Control for input subroutine
; ----------------------------
;
;; WAIT-KEY
L15D4: BIT 5,(IY+$02) ; test TV_FLAG - clear lower screen ?
JR NZ,L15DE ; forward to WAIT-KEY1 if so.
SET 3,(IY+$02) ; update TV_FLAG - signal reprint the edit
; line to the lower screen.
;; WAIT-KEY1
L15DE: CALL L15E6 ; routine INPUT-AD is called.
RET C ; return with acceptable keys.
JR Z,L15DE ; back to WAIT-KEY1 if no key is pressed
; or it has been handled within INPUT-AD.
; Note. When inputting from the keyboard all characters are returned with
; above conditions so this path is never taken.
;; REPORT-8
L15E4: RST 08H ; ERROR-1
DB $07 ; Error Report: End of file
; ------------------------------
; Make HL point to input address
; ------------------------------
; This routine fetches the address of the input stream from the current
; channel area using system variable CURCHL.
;; INPUT-AD
L15E6: EXX ; switch in alternate set.
PUSH HL ; save HL register
LD HL,($5C51) ; fetch address of CURCHL - current channel.
INC HL ; step over output routine
INC HL ; to point to low byte of input routine.
JR L15F7 ; forward to CALL-SUB.
; -------------------
; Main Output Routine
; -------------------
; The entry point OUT-CODE is called on five occasions to print
; the ASCII equivalent of a value 0-9.
;
; PRINT-A-2 is a continuation of the RST 10 to print any character.
; Both print to the current channel and the printing of control codes
; may alter that channel to divert subsequent RST 10 instructions
; to temporary routines. The normal channel is $09F4.
;; OUT-CODE
L15EF: LD E,$30 ; add 48 decimal to give ASCII
ADD A,E ; character '0' to '9'.
;; PRINT-A-2
L15F2: EXX ; switch in alternate set
PUSH HL ; save HL register
LD HL,($5C51) ; fetch CURCHL the current channel.
; input-ad rejoins here also.
;; CALL-SUB
L15F7: LD E,(HL) ; put the low byte in E.
INC HL ; advance address.
LD D,(HL) ; put the high byte to D.
EX DE,HL ; transfer the stream to HL.
CALL L162C ; use routine CALL-JUMP.
; in effect CALL (HL).
POP HL ; restore saved HL register.
EXX ; switch back to the main set and
RET ; return.
; ------------
; Open channel
; ------------
; This subroutine is used by the ROM to open a channel 'K', 'S', 'R' or 'P'.
; This is either for its own use or in response to a user's request, for
; example, when '#' is encountered with output - PRINT, LIST etc.
; or with input - INPUT, INKEY$ etc.
; it is entered with a system stream $FD - $FF, or a user stream $00 - $0F
; in the accumulator.
;; CHAN-OPEN
L1601: ADD A,A ; double the stream ($FF will become $FE etc.)
ADD A,$16 ; add the offset to stream 0 from $5C00
LD L,A ; result to L
LD H,$5C ; now form the address in STRMS area.
LD E,(HL) ; fetch low byte of CHANS offset
INC HL ; address next
LD D,(HL) ; fetch high byte of offset
LD A,D ; test that the stream is open.
OR E ; zero if closed.
JR NZ,L1610 ; forward to CHAN-OP-1 if open.
;; REPORT-Oa
L160E: RST 08H ; ERROR-1
DB $17 ; Error Report: Invalid stream
; continue here if stream was open. Note that the offset is from CHANS
; to the second byte of the channel.
;; CHAN-OP-1
L1610: DEC DE ; reduce offset so it points to the channel.
LD HL,($5C4F) ; fetch CHANS the location of the base of
; the channel information area
ADD HL,DE ; and add the offset to address the channel.
; and continue to set flags.
; -----------------
; Set channel flags
; -----------------
; This subroutine is used from ED-EDIT, str$ and read-in to reset the
; current channel when it has been temporarily altered.
;; CHAN-FLAG
L1615: LD ($5C51),HL ; set CURCHL system variable to the
; address in HL
RES 4,(IY+$30) ; update FLAGS2 - signal K channel not in use.
; Note. provide a default for channel 'R'.
INC HL ; advance past
INC HL ; output routine.
INC HL ; advance past
INC HL ; input routine.
LD C,(HL) ; pick up the letter.
LD HL,L162D ; address: chn-cd-lu
CALL L16DC ; routine INDEXER finds offset to a
; flag-setting routine.
RET NC ; but if the letter wasn't found in the
; table just return now. - channel 'R'.
LD D,$00 ; prepare to add
LD E,(HL) ; offset to E
ADD HL,DE ; add offset to location of offset to form
; address of routine
;; CALL-JUMP
L162C: JP (HL) ; jump to the routine
; Footnote. calling any location that holds JP (HL) is the equivalent to
; a pseudo Z80 instruction CALL (HL). The ROM uses the instruction above.
; --------------------------
; Channel code look-up table
; --------------------------
; This table is used by the routine above to find one of the three
; flag setting routines below it.
; A zero end-marker is required as channel 'R' is not present.
;; chn-cd-lu
L162D: DB 'K', L1634-$-1 ; offset $06 to CHAN-K
DB 'S', L1642-$-1 ; offset $12 to CHAN-S
DB 'P', L164D-$-1 ; offset $1B to CHAN-P
DB $00 ; end marker.
; --------------
; Channel K flag
; --------------
; routine to set flags for lower screen/keyboard channel.
;; CHAN-K
L1634: SET 0,(IY+$02) ; update TV_FLAG - signal lower screen in use
RES 5,(IY+$01) ; update FLAGS - signal no new key
SET 4,(IY+$30) ; update FLAGS2 - signal K channel in use
JR L1646 ; forward to CHAN-S-1 for indirect exit
; --------------
; Channel S flag
; --------------
; routine to set flags for upper screen channel.
;; CHAN-S
L1642: RES 0,(IY+$02) ; TV_FLAG - signal main screen in use
;; CHAN-S-1
L1646: RES 1,(IY+$01) ; update FLAGS - signal printer not in use
JP L0D4D ; jump back to TEMPS and exit via that
; routine after setting temporary attributes.
; --------------
; Channel P flag
; --------------
; This routine sets a flag so that subsequent print related commands
; print to printer or update the relevant system variables.
; This status remains in force until reset by the routine above.
;; CHAN-P
L164D: SET 1,(IY+$01) ; update FLAGS - signal printer in use
RET ; return
; -----------------------
; Just one space required
; -----------------------
; This routine is called once only to create a single space
; in workspace by ADD-CHAR. It is slightly quicker than using a RST $30.
; There are several instances in the calculator where the sequence
; ld bc, 1; rst $30 could be replaced by a call to this routine but it
; only gives a saving of one byte each time.
;; ONE-SPACE
L1652: LD BC,$0001 ; create space for a single character.
; ---------
; Make Room
; ---------
; This entry point is used to create BC spaces in various areas such as
; program area, variables area, workspace etc..
; The entire free RAM is available to each BASIC statement.
; On entry, HL addresses where the first location is to be created.
; Afterwards, HL will point to the location before this.
;; MAKE-ROOM
L1655: PUSH HL ; save the address pointer.
CALL L1F05 ; routine TEST-ROOM checks if room
; exists and generates an error if not.
POP HL ; restore the address pointer.
CALL L1664 ; routine POINTERS updates the
; dynamic memory location pointers.
; DE now holds the old value of STKEND.
LD HL,($5C65) ; fetch new STKEND the top destination.
EX DE,HL ; HL now addresses the top of the area to
; be moved up - old STKEND.
LDDR ; the program, variables, etc are moved up.
RET ; return with new area ready to be populated.
; HL points to location before new area,
; and DE to last of new locations.
; -----------------------------------------------
; Adjust pointers before making or reclaiming room
; -----------------------------------------------
; This routine is called by MAKE-ROOM to adjust upwards and by RECLAIM to
; adjust downwards the pointers within dynamic memory.
; The fourteen pointers to dynamic memory, starting with VARS and ending
; with STKEND, are updated adding BC if they are higher than the position
; in HL.
; The system variables are in no particular order except that STKEND, the first
; free location after dynamic memory must be the last encountered.
;; POINTERS
L1664: PUSH AF ; preserve accumulator.
PUSH HL ; put pos pointer on stack.
LD HL,$5C4B ; address VARS the first of the
LD A,$0E ; fourteen variables to consider.
;; PTR-NEXT
L166B: LD E,(HL) ; fetch the low byte of the system variable.
INC HL ; advance address.
LD D,(HL) ; fetch high byte of the system variable.
EX (SP),HL ; swap pointer on stack with the variable
; pointer.
AND A ; prepare to subtract.
SBC HL,DE ; subtract variable address
ADD HL,DE ; and add back
EX (SP),HL ; swap pos with system variable pointer
JR NC,L167F ; forward to PTR-DONE if var before pos
PUSH DE ; save system variable address.
EX DE,HL ; transfer to HL
ADD HL,BC ; add the offset
EX DE,HL ; back to DE
LD (HL),D ; load high byte
DEC HL ; move back
LD (HL),E ; load low byte
INC HL ; advance to high byte
POP DE ; restore old system variable address.
;; PTR-DONE
L167F: INC HL ; address next system variable.
DEC A ; decrease counter.
JR NZ,L166B ; back to PTR-NEXT if more.
EX DE,HL ; transfer old value of STKEND to HL.
; Note. this has always been updated.
POP DE ; pop the address of the position.
POP AF ; pop preserved accumulator.
AND A ; clear carry flag preparing to subtract.
SBC HL,DE ; subtract position from old stkend
LD B,H ; to give number of data bytes
LD C,L ; to be moved.
INC BC ; increment as we also copy byte at old STKEND.
ADD HL,DE ; recompute old stkend.
EX DE,HL ; transfer to DE.
RET ; return.
; -------------------
; Collect line number
; -------------------
; This routine extracts a line number, at an address that has previously
; been found using LINE-ADDR, and it is entered at LINE-NO. If it encounters
; the program 'end-marker' then the previous line is used and if that
; should also be unacceptable then zero is used as it must be a direct
; command. The program end-marker is the variables end-marker $80, or
; if variables exist, then the first character of any variable name.
;; LINE-ZERO
L168F: DB $00, $00 ; dummy line number used for direct commands
;; LINE-NO-A
L1691: EX DE,HL ; fetch the previous line to HL and set
LD DE,$168F ; DE to LINE-ZERO should HL also fail.
; -> The Entry Point.
;; LINE-NO
L1695: LD A,(HL) ; fetch the high byte - max $2F
AND $C0 ; mask off the invalid bits.
JR NZ,L1691 ; to LINE-NO-A if an end-marker.
LD D,(HL) ; reload the high byte.
INC HL ; advance address.
LD E,(HL) ; pick up the low byte.
RET ; return from here.
; -------------------
; Handle reserve room
; -------------------
; This is a continuation of the restart BC-SPACES
;; RESERVE
L169E: LD HL,($5C63) ; STKBOT first location of calculator stack
DEC HL ; make one less than new location
CALL L1655 ; routine MAKE-ROOM creates the room.
INC HL ; address the first new location
INC HL ; advance to second
POP BC ; restore old WORKSP
LD ($5C61),BC ; system variable WORKSP was perhaps
; changed by POINTERS routine.
POP BC ; restore count for return value.
EX DE,HL ; switch. DE = location after first new space
INC HL ; HL now location after new space
RET ; return.
; ---------------------------
; Clear various editing areas
; ---------------------------
; This routine sets the editing area, workspace and calculator stack
; to their minimum configurations as at initialization and indeed this
; routine could have been relied on to perform that task.
; This routine uses HL only and returns with that register holding
; WORKSP/STKBOT/STKEND though no use is made of this. The routines also
; reset MEM to its usual place in the systems variable area should it
; have been relocated to a FOR-NEXT variable. The main entry point
; SET-MIN is called at the start of the MAIN-EXEC loop and prior to
; displaying an error.
;; SET-MIN
L16B0: LD HL,($5C59) ; fetch E_LINE
LD (HL),$0D ; insert carriage return
LD ($5C5B),HL ; make K_CUR keyboard cursor point there.
INC HL ; next location
LD (HL),$80 ; holds end-marker $80
INC HL ; next location becomes
LD ($5C61),HL ; start of WORKSP
; This entry point is used prior to input and prior to the execution,
; or parsing, of each statement.
;; SET-WORK
L16BF: LD HL,($5C61) ; fetch WORKSP value
LD ($5C63),HL ; and place in STKBOT
; This entry point is used to move the stack back to its normal place
; after temporary relocation during line entry and also from ERROR-3
;; SET-STK
L16C5: LD HL,($5C63) ; fetch STKBOT value
LD ($5C65),HL ; and place in STKEND.
PUSH HL ; perhaps an obsolete entry point.
LD HL,$5C92 ; normal location of MEM-0
LD ($5C68),HL ; is restored to system variable MEM.
POP HL ; saved value not required.
RET ; return.
; ------------------
; Reclaim edit-line?
; ------------------
; This seems to be legacy code from the ZX80/ZX81 as it is
; not used in this ROM.
; That task, in fact, is performed here by the dual-area routine CLEAR-SP.
; This routine is designed to deal with something that is known to be in the
; edit buffer and not workspace.
; On entry, HL must point to the end of the something to be deleted.
;; REC-EDIT
L16D4: LD DE,($5C59) ; fetch start of edit line from E_LINE.
JP L19E5 ; jump forward to RECLAIM-1.
; --------------------------
; The Table INDEXING routine
; --------------------------
; This routine is used to search two-byte hash tables for a character
; held in C, returning the address of the following offset byte.
; if it is known that the character is in the table e.g. for priorities,
; then the table requires no zero end-marker. If this is not known at the
; outset then a zero end-marker is required and carry is set to signal
; success.
;; INDEXER-1
L16DB: INC HL ; address the next pair of values.
; -> The Entry Point.
;; INDEXER
L16DC: LD A,(HL) ; fetch the first byte of pair
AND A ; is it the end-marker ?
RET Z ; return with carry reset if so.
CP C ; is it the required character ?
INC HL ; address next location.
JR NZ,L16DB ; back to INDEXER-1 if no match.
SCF ; else set the carry flag.
RET ; return with carry set
; --------------------------------
; The Channel and Streams Routines
; --------------------------------
; A channel is an input/output route to a hardware device
; and is identified to the system by a single letter e.g. 'K' for
; the keyboard. A channel can have an input and output route
; associated with it in which case it is bi-directional like
; the keyboard. Others like the upper screen 'S' are output
; only and the input routine usually points to a report message.
; Channels 'K' and 'S' are system channels and it would be inappropriate
; to close the associated streams so a mechanism is provided to
; re-attach them. When the re-attachment is no longer required, then
; closing these streams resets them as at initialization.
; The same also would have applied to channel 'R', the RS232 channel
; as that is used by the system. It's input stream seems to have been
; removed and it is not available to the user. However the channel could
; not be removed entirely as its output routine was used by the system.
; As a result of removing this channel, channel 'P', the printer is
; erroneously treated as a system channel.
; Ironically the tape streamer is not accessed through streams and
; channels.
; Early demonstrations of the Spectrum showed a single microdrive being
; controlled by this ROM. Adverts also said that the network and RS232
; were in this ROM. Channels 'M' and 'N' are user channels and have been
; removed successfully if, as seems vaguely possible, they existed.
; ---------------------
; Handle CLOSE# command
; ---------------------
; This command allows streams to be closed after use.
; Any temporary memory areas used by the stream would be reclaimed and
; finally flags set or reset if necessary.
;; CLOSE
L16E5: CALL L171E ; routine STR-DATA fetches parameter
; from calculator stack and gets the
; existing STRMS data pointer address in HL
; and stream offset from CHANS in BC.
; Note. this offset could be zero if the
; stream is already closed. A check for this
; should occur now and an error should be
; generated, for example,
; Report S 'Stream already closed'.
CALL L1701 ; routine CLOSE-2 would perform any actions
; peculiar to that stream without disturbing
; data pointer to STRMS entry in HL.
LD BC,$0000 ; the stream is to be blanked.
LD DE,$A3E2 ; the number of bytes from stream 4, $5C1E,
; to $10000
EX DE,HL ; transfer offset to HL, STRMS data pointer
; to DE.
ADD HL,DE ; add the offset to the data pointer.
JR C,L16FC ; forward to CLOSE-1 if a non-system stream.
; i.e. higher than 3.
; proceed with a negative result.
LD BC,L15C6 + 14 ; prepare the address of the byte after
; the initial stream data in ROM. ($15D4)
ADD HL,BC ; index into the data table with negative value.
LD C,(HL) ; low byte to C
INC HL ; address next.
LD B,(HL) ; high byte to B.
; and for streams 0 - 3 just enter the initial data back into the STRMS entry
; streams 0 - 2 can't be closed as they are shared by the operating system.
; -> for streams 4 - 15 then blank the entry.
;; CLOSE-1
L16FC: EX DE,HL ; address of stream to HL.
LD (HL),C ; place zero (or low byte).
INC HL ; next address.
LD (HL),B ; place zero (or high byte).
RET ; return.
; ------------------
; CLOSE-2 Subroutine
; ------------------
; There is not much point in coming here.
; The purpose was once to find the offset to a special closing routine,
; in this ROM and within 256 bytes of the close stream look up table that
; would reclaim any buffers associated with a stream. At least one has been
; removed.
;; CLOSE-2
L1701: PUSH HL ; * save address of stream data pointer
; in STRMS on the machine stack.
LD HL,($5C4F) ; fetch CHANS address to HL
ADD HL,BC ; add the offset to address the second
; byte of the output routine hopefully.
INC HL ; step past
INC HL ; the input routine.
INC HL ; to address channel's letter
LD C,(HL) ; pick it up in C.
; Note. but if stream is already closed we
; get the value $10 (the byte preceding 'K').
EX DE,HL ; save the pointer to the letter in DE.
LD HL,L1716 ; address: cl-str-lu in ROM.
CALL L16DC ; routine INDEXER uses the code to get
; the 8-bit offset from the current point to
; the address of the closing routine in ROM.
; Note. it won't find $10 there!
LD C,(HL) ; transfer the offset to C.
LD B,$00 ; prepare to add.
ADD HL,BC ; add offset to point to the address of the
; routine that closes the stream.
; (and presumably removes any buffers that
; are associated with it.)
JP (HL) ; jump to that routine.
; --------------------------
; CLOSE stream look-up table
; --------------------------
; This table contains an entry for a letter found in the CHANS area.
; followed by an 8-bit displacement, from that byte's address in the
; table to the routine that performs any ancillary actions associated
; with closing the stream of that channel.
; The table doesn't require a zero end-marker as the letter has been
; picked up from a channel that has an open stream.
;; cl-str-lu
L1716: DB 'K', L171C-$-1 ; offset 5 to CLOSE-STR
DB 'S', L171C-$-1 ; offset 3 to CLOSE-STR
DB 'P', L171C-$-1 ; offset 1 to CLOSE-STR
; ------------------------
; Close Stream Subroutines
; ------------------------
; The close stream routines in fact have no ancillary actions to perform
; which is not surprising with regard to 'K' and 'S'.
;; CLOSE-STR
L171C: POP HL ; * now just restore the stream data pointer
RET ; in STRMS and return.
; -----------
; Stream data
; -----------
; This routine finds the data entry in the STRMS area for the specified
; stream which is passed on the calculator stack. It returns with HL
; pointing to this system variable and BC holding a displacement from
; the CHANS area to the second byte of the stream's channel. If BC holds
; zero, then that signifies that the stream is closed.
;; STR-DATA
L171E: CALL L1E94 ; routine FIND-INT1 fetches parameter to A
CP $10 ; is it less than 16d ?
JR C,L1727 ; skip forward to STR-DATA1 if so.
;; REPORT-Ob
L1725: RST 08H ; ERROR-1
DB $17 ; Error Report: Invalid stream
;; STR-DATA1
L1727: ADD A,$03 ; add the offset for 3 system streams.
; range 00 - 15d becomes 3 - 18d.
RLCA ; double as there are two bytes per
; stream - now 06 - 36d
LD HL,$5C10 ; address STRMS - the start of the streams
; data area in system variables.
LD C,A ; transfer the low byte to A.
LD B,$00 ; prepare to add offset.
ADD HL,BC ; add to address the data entry in STRMS.
; the data entry itself contains an offset from CHANS to the address of the
; stream
LD C,(HL) ; low byte of displacement to C.
INC HL ; address next.
LD B,(HL) ; high byte of displacement to B.
DEC HL ; step back to leave HL pointing to STRMS
; data entry.
RET ; return with CHANS displacement in BC
; and address of stream data entry in HL.
; --------------------
; Handle OPEN# command
; --------------------
; Command syntax example: OPEN #5,"s"
; On entry the channel code entry is on the calculator stack with the next
; value containing the stream identifier. They have to swapped.
;; OPEN
L1736: RST 28H ;; FP-CALC ;s,c.
DB $01 ;;exchange ;c,s.
DB $38 ;;end-calc
CALL L171E ; routine STR-DATA fetches the stream off
; the stack and returns with the CHANS
; displacement in BC and HL addressing
; the STRMS data entry.
LD A,B ; test for zero which
OR C ; indicates the stream is closed.
JR Z,L1756 ; skip forward to OPEN-1 if so.
; if it is a system channel then it can re-attached.
EX DE,HL ; save STRMS address in DE.
LD HL,($5C4F) ; fetch CHANS.
ADD HL,BC ; add the offset to address the second
; byte of the channel.
INC HL ; skip over the
INC HL ; input routine.
INC HL ; and address the letter.
LD A,(HL) ; pick up the letter.
EX DE,HL ; save letter pointer and bring back
; the STRMS pointer.
CP $4B ; is it 'K' ?
JR Z,L1756 ; forward to OPEN-1 if so
CP $53 ; is it 'S' ?
JR Z,L1756 ; forward to OPEN-1 if so
CP $50 ; is it 'P' ?
JR NZ,L1725 ; back to REPORT-Ob if not.
; to report 'Invalid stream'.
; continue if one of the upper-case letters was found.
; and rejoin here from above if stream was closed.
;; OPEN-1
L1756: CALL L175D ; routine OPEN-2 opens the stream.
; it now remains to update the STRMS variable.
LD (HL),E ; insert or overwrite the low byte.
INC HL ; address high byte in STRMS.
LD (HL),D ; insert or overwrite the high byte.
RET ; return.
; -----------------
; OPEN-2 Subroutine
; -----------------
; There is some point in coming here as, as well as once creating buffers,
; this routine also sets flags.
;; OPEN-2
L175D: PUSH HL ; * save the STRMS data entry pointer.
CALL L2BF1 ; routine STK-FETCH now fetches the
; parameters of the channel string.
; start in DE, length in BC.
LD A,B ; test that it is not
OR C ; the null string.
JR NZ,L1767 ; skip forward to OPEN-3 with 1 character
; or more!
;; REPORT-Fb
L1765: RST 08H ; ERROR-1
DB $0E ; Error Report: Invalid file name
;; OPEN-3
L1767: PUSH BC ; save the length of the string.
LD A,(DE) ; pick up the first character.
; Note. if the second character is used to
; distinguish between a binary or text
; channel then it will be simply a matter
; of setting bit 7 of FLAGX.
AND $DF ; make it upper-case.
LD C,A ; place it in C.
LD HL,L177A ; address: op-str-lu is loaded.
CALL L16DC ; routine INDEXER will search for letter.
JR NC,L1765 ; back to REPORT-F if not found
; 'Invalid filename'
LD C,(HL) ; fetch the displacement to opening routine.
LD B,$00 ; prepare to add.
ADD HL,BC ; now form address of opening routine.
POP BC ; restore the length of string.
JP (HL) ; now jump forward to the relevant routine.
; -------------------------
; OPEN stream look-up table
; -------------------------
; The open stream look-up table consists of matched pairs.
; The channel letter is followed by an 8-bit displacement to the
; associated stream-opening routine in this ROM.
; The table requires a zero end-marker as the letter has been
; provided by the user and not the operating system.
;; op-str-lu
L177A: DB 'K', L1781-$-1 ; $06 offset to OPEN-K
DB 'S', L1785-$-1 ; $08 offset to OPEN-S
DB 'P', L1789-$-1 ; $0A offset to OPEN-P
DB $00 ; end-marker.
; ----------------------------
; The Stream Opening Routines.
; ----------------------------
; These routines would have opened any buffers associated with the stream
; before jumping forward to to OPEN-END with the displacement value in E
; and perhaps a modified value in BC. The strange pathing does seem to
; provide for flexibility in this respect.
;
; There is no need to open the printer buffer as it is there already
; even if you are still saving up for a ZX Printer or have moved onto
; something bigger. In any case it would have to be created after
; the system variables but apart from that it is a simple task
; and all but one of the ROM routines can handle a buffer in that position.
; (PR-ALL-6 would require an extra 3 bytes of code).
; However it wouldn't be wise to have two streams attached to the ZX Printer
; as you can now, so one assumes that if PR_CC_hi was non-zero then
; the OPEN-P routine would have refused to attach a stream if another
; stream was attached.
; Something of significance is being passed to these ghost routines in the
; second character. Strings 'RB', 'RT' perhaps or a drive/station number.
; The routine would have to deal with that and exit to OPEN_END with BC
; containing $0001 or more likely there would be an exit within the routine.
; Anyway doesn't matter, these routines are long gone.
; -----------------
; OPEN-K Subroutine
; -----------------
; Open Keyboard stream.
;; OPEN-K
L1781: LD E,$01 ; 01 is offset to second byte of channel 'K'.
JR L178B ; forward to OPEN-END
; -----------------
; OPEN-S Subroutine
; -----------------
; Open Screen stream.
;; OPEN-S
L1785: LD E,$06 ; 06 is offset to 2nd byte of channel 'S'
JR L178B ; to OPEN-END
; -----------------
; OPEN-P Subroutine
; -----------------
; Open Printer stream.
;; OPEN-P
L1789: LD E,$10 ; 16d is offset to 2nd byte of channel 'P'
;; OPEN-END
L178B: DEC BC ; the stored length of 'K','S','P' or
; whatever is now tested. ??
LD A,B ; test now if initial or residual length
OR C ; is one character.
JR NZ,L1765 ; to REPORT-Fb 'Invalid file name' if not.
LD D,A ; load D with zero to form the displacement
; in the DE register.
POP HL ; * restore the saved STRMS pointer.
RET ; return to update STRMS entry thereby
; signaling stream is open.
; ----------------------------------------
; Handle CAT, ERASE, FORMAT, MOVE commands
; ----------------------------------------
; These just generate an error report as the ROM is 'incomplete'.
;
; Luckily this provides a mechanism for extending these in a shadow ROM
; but without the powerful mechanisms set up in this ROM.
; An instruction fetch on $0008 may page in a peripheral ROM,
; e.g. the Sinclair Interface 1 ROM, to handle these commands.
; However that wasn't the plan.
; Development of this ROM continued for another three months until the cost
; of replacing it and the manual became unfeasible.
; The ultimate power of channels and streams died at birth.
;; CAT-ETC
L1793: JR L1725 ; to REPORT-Ob
; -----------------
; Perform AUTO-LIST
; -----------------
; This produces an automatic listing in the upper screen.
;; AUTO-LIST
L1795: LD ($5C3F),SP ; save stack pointer in LIST_SP
LD (IY+$02),$10 ; update TV_FLAG set bit 3
CALL L0DAF ; routine CL-ALL.
SET 0,(IY+$02) ; update TV_FLAG - signal lower screen in use
LD B,(IY+$31) ; fetch DF_SZ to B.
CALL L0E44 ; routine CL-LINE clears lower display
; preserving B.
RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use
SET 0,(IY+$30) ; update FLAGS2 - signal unnecessary to
; clear main screen.
LD HL,($5C49) ; fetch E_PPC current edit line to HL.
LD DE,($5C6C) ; fetch S_TOP to DE, the current top line
; (initially zero)
AND A ; prepare for true subtraction.
SBC HL,DE ; subtract and
ADD HL,DE ; add back.
JR C,L17E1 ; to AUTO-L-2 if S_TOP higher than E_PPC
; to set S_TOP to E_PPC
PUSH DE ; save the top line number.
CALL L196E ; routine LINE-ADDR gets address of E_PPC.
LD DE,$02C0 ; prepare known number of characters in
; the default upper screen.
EX DE,HL ; offset to HL, program address to DE.
SBC HL,DE ; subtract high value from low to obtain
; negated result used in addition.
EX (SP),HL ; swap result with top line number on stack.
CALL L196E ; routine LINE-ADDR gets address of that
; top line in HL and next line in DE.
POP BC ; restore the result to balance stack.
;; AUTO-L-1
L17CE: PUSH BC ; save the result.
CALL L19B8 ; routine NEXT-ONE gets address in HL of
; line after auto-line (in DE).
POP BC ; restore result.
ADD HL,BC ; compute back.
JR C,L17E4 ; to AUTO-L-3 if line 'should' appear
EX DE,HL ; address of next line to HL.
LD D,(HL) ; get line
INC HL ; number
LD E,(HL) ; in DE.
DEC HL ; adjust back to start.
LD ($5C6C),DE ; update S_TOP.
JR L17CE ; to AUTO-L-1 until estimate reached.
; ---
; the jump was to here if S_TOP was greater than E_PPC
;; AUTO-L-2
L17E1: LD ($5C6C),HL ; make S_TOP the same as E_PPC.
; continue here with valid starting point from above or good estimate
; from computation
;; AUTO-L-3
L17E4: LD HL,($5C6C) ; fetch S_TOP line number to HL.
CALL L196E ; routine LINE-ADDR gets address in HL.
; address of next in DE.
JR Z,L17ED ; to AUTO-L-4 if line exists.
EX DE,HL ; else use address of next line.
;; AUTO-L-4
L17ED: CALL L1833 ; routine LIST-ALL >>>
; The return will be to here if no scrolling occurred
RES 4,(IY+$02) ; update TV_FLAG - signal no auto listing.
RET ; return.
; ------------
; Handle LLIST
; ------------
; A short form of LIST #3. The listing goes to stream 3 - default printer.
;; LLIST
L17F5: LD A,$03 ; the usual stream for ZX Printer
JR L17FB ; forward to LIST-1
; -----------
; Handle LIST
; -----------
; List to any stream.
; Note. While a starting line can be specified it is
; not possible to specify an end line.
; Just listing a line makes it the current edit line.
;; LIST
L17F9: LD A,$02 ; default is stream 2 - the upper screen.
;; LIST-1
L17FB: LD (IY+$02),$00 ; the TV_FLAG is initialized with bit 0 reset
; indicating upper screen in use.
CALL L2530 ; routine SYNTAX-Z - checking syntax ?
CALL NZ,L1601 ; routine CHAN-OPEN if in run-time.
RST 18H ; GET-CHAR
CALL L2070 ; routine STR-ALTER will alter if '#'.
JR C,L181F ; forward to LIST-4 not a '#' .
RST 18H ; GET-CHAR
CP $3B ; is it ';' ?
JR Z,L1814 ; skip to LIST-2 if so.
CP $2C ; is it ',' ?
JR NZ,L181A ; forward to LIST-3 if neither separator.
; we have, say, LIST #15, and a number must follow the separator.
;; LIST-2
L1814: RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM
JR L1822 ; forward to LIST-5
; ---
; the branch was here with just LIST #3 etc.
;; LIST-3
L181A: CALL L1CE6 ; routine USE-ZERO
JR L1822 ; forward to LIST-5
; ---
; the branch was here with LIST
;; LIST-4
L181F: CALL L1CDE ; routine FETCH-NUM checks if a number
; follows else uses zero.
;; LIST-5
L1822: CALL L1BEE ; routine CHECK-END quits if syntax OK >>>
CALL L1E99 ; routine FIND-INT2 fetches the number
; from the calculator stack in run-time.
LD A,B ; fetch high byte of line number and
AND $3F ; make less than $40 so that NEXT-ONE
; (from LINE-ADDR) doesn't lose context.
; Note. this is not satisfactory and the typo
; LIST 20000 will list an entirely different
; section than LIST 2000. Such typos are not
; available for checking if they are direct
; commands.
LD H,A ; transfer the modified
LD L,C ; line number to HL.
LD ($5C49),HL ; update E_PPC to new line number.
CALL L196E ; routine LINE-ADDR gets the address of the
; line.
; This routine is called from AUTO-LIST
;; LIST-ALL
L1833: LD E,$01 ; signal current line not yet printed
;; LIST-ALL-2
L1835: CALL L1855 ; routine OUT-LINE outputs a BASIC line
; using PRINT-OUT and makes an early return
; when no more lines to print. >>>
RST 10H ; PRINT-A prints the carriage return (in A)
BIT 4,(IY+$02) ; test TV_FLAG - automatic listing ?
JR Z,L1835 ; back to LIST-ALL-2 if not
; (loop exit is via OUT-LINE)
; continue here if an automatic listing required.
LD A,($5C6B) ; fetch DF_SZ lower display file size.
SUB (IY+$4F) ; subtract S_POSN_hi ithe current line number.
JR NZ,L1835 ; back to LIST-ALL-2 if upper screen not full.
XOR E ; A contains zero, E contains one if the
; current edit line has not been printed
; or zero if it has (from OUT-LINE).
RET Z ; return if the screen is full and the line
; has been printed.
; continue with automatic listings if the screen is full and the current
; edit line is missing. OUT-LINE will scroll automatically.
PUSH HL ; save the pointer address.
PUSH DE ; save the E flag.
LD HL,$5C6C ; fetch S_TOP the rough estimate.
CALL L190F ; routine LN-FETCH updates S_TOP with
; the number of the next line.
POP DE ; restore the E flag.
POP HL ; restore the address of the next line.
JR L1835 ; back to LIST-ALL-2.
; ------------------------
; Print a whole BASIC line
; ------------------------
; This routine prints a whole BASIC line and it is called
; from LIST-ALL to output the line to current channel
; and from ED-EDIT to 'sprint' the line to the edit buffer.
;; OUT-LINE
L1855: LD BC,($5C49) ; fetch E_PPC the current line which may be
; unchecked and not exist.
CALL L1980 ; routine CP-LINES finds match or line after.
LD D,$3E ; prepare cursor '>' in D.
JR Z,L1865 ; to OUT-LINE1 if matched or line after.
LD DE,$0000 ; put zero in D, to suppress line cursor.
RL E ; pick up carry in E if line before current
; leave E zero if same or after.
;; OUT-LINE1
L1865: LD (IY+$2D),E ; save flag in BREG which is spare.
LD A,(HL) ; get high byte of line number.
CP $40 ; is it too high ($2F is maximum possible) ?
POP BC ; drop the return address and
RET NC ; make an early return if so >>>
PUSH BC ; save return address
CALL L1A28 ; routine OUT-NUM-2 to print addressed number
; with leading space.
INC HL ; skip low number byte.
INC HL ; and the two
INC HL ; length bytes.
RES 0,(IY+$01) ; update FLAGS - signal leading space required.
LD A,D ; fetch the cursor.
AND A ; test for zero.
JR Z,L1881 ; to OUT-LINE3 if zero.
RST 10H ; PRINT-A prints '>' the current line cursor.
; this entry point is called from ED-COPY
;; OUT-LINE2
L187D: SET 0,(IY+$01) ; update FLAGS - suppress leading space.
;; OUT-LINE3
L1881: PUSH DE ; save flag E for a return value.
EX DE,HL ; save HL address in DE.
RES 2,(IY+$30) ; update FLAGS2 - signal NOT in QUOTES.
LD HL,$5C3B ; point to FLAGS.
RES 2,(HL) ; signal 'K' mode. (starts before keyword)
BIT 5,(IY+$37) ; test FLAGX - input mode ?
JR Z,L1894 ; forward to OUT-LINE4 if not.
SET 2,(HL) ; signal 'L' mode. (used for input)
;; OUT-LINE4
L1894: LD HL,($5C5F) ; fetch X_PTR - possibly the error pointer
; address.
AND A ; clear the carry flag.
SBC HL,DE ; test if an error address has been reached.
JR NZ,L18A1 ; forward to OUT-LINE5 if not.
LD A,$3F ; load A with '?' the error marker.
CALL L18C1 ; routine OUT-FLASH to print flashing marker.
;; OUT-LINE5
L18A1: CALL L18E1 ; routine OUT-CURS will print the cursor if
; this is the right position.
EX DE,HL ; restore address pointer to HL.
LD A,(HL) ; fetch the addressed character.
CALL L18B6 ; routine NUMBER skips a hidden floating
; point number if present.
INC HL ; now increment the pointer.
CP $0D ; is character end-of-line ?
JR Z,L18B4 ; to OUT-LINE6, if so, as line is finished.
EX DE,HL ; save the pointer in DE.
CALL L1937 ; routine OUT-CHAR to output character/token.
JR L1894 ; back to OUT-LINE4 until entire line is done.
; ---
;; OUT-LINE6
L18B4: POP DE ; bring back the flag E, zero if current
; line printed else 1 if still to print.
RET ; return with A holding $0D
; -------------------------
; Check for a number marker
; -------------------------
; this subroutine is called from two processes. while outputting BASIC lines
; and while searching statements within a BASIC line.
; during both, this routine will pass over an invisible number indicator
; and the five bytes floating-point number that follows it.
; Note that this causes floating point numbers to be stripped from
; the BASIC line when it is fetched to the edit buffer by OUT_LINE.
; the number marker also appears after the arguments of a DEF FN statement
; and may mask old 5-byte string parameters.
;; NUMBER
L18B6: CP $0E ; character fourteen ?
RET NZ ; return if not.
INC HL ; skip the character
INC HL ; and five bytes
INC HL ; following.
INC HL ;
INC HL ;
INC HL ;
LD A,(HL) ; fetch the following character
RET ; for return value.
; --------------------------
; Print a flashing character
; --------------------------
; This subroutine is called from OUT-LINE to print a flashing error
; marker '?' or from the next routine to print a flashing cursor e.g. 'L'.
; However, this only gets called from OUT-LINE when printing the edit line
; or the input buffer to the lower screen so a direct call to $09F4 can
; be used, even though out-line outputs to other streams.
; In fact the alternate set is used for the whole routine.
;; OUT-FLASH
L18C1: EXX ; switch in alternate set
LD HL,($5C8F) ; fetch L = ATTR_T, H = MASK-T
PUSH HL ; save masks.
RES 7,H ; reset flash mask bit so active.
SET 7,L ; make attribute FLASH.
LD ($5C8F),HL ; resave ATTR_T and MASK-T
LD HL,$5C91 ; address P_FLAG
LD D,(HL) ; fetch to D
PUSH DE ; and save.
LD (HL),$00 ; clear inverse, over, ink/paper 9
CALL L09F4 ; routine PRINT-OUT outputs character
; without the need to vector via RST 10.
POP HL ; pop P_FLAG to H.
LD (IY+$57),H ; and restore system variable P_FLAG.
POP HL ; restore temporary masks
LD ($5C8F),HL ; and restore system variables ATTR_T/MASK_T
EXX ; switch back to main set
RET ; return
; ----------------
; Print the cursor
; ----------------
; This routine is called before any character is output while outputting
; a BASIC line or the input buffer. This includes listing to a printer
; or screen, copying a BASIC line to the edit buffer and printing the
; input buffer or edit buffer to the lower screen. It is only in the
; latter two cases that it has any relevance and in the last case it
; performs another very important function also.
;; OUT-CURS
L18E1: LD HL,($5C5B) ; fetch K_CUR the current cursor address
AND A ; prepare for true subtraction.
SBC HL,DE ; test against pointer address in DE and
RET NZ ; return if not at exact position.
; the value of MODE, maintained by KEY-INPUT, is tested and if non-zero
; then this value 'E' or 'G' will take precedence.
LD A,($5C41) ; fetch MODE 0='KLC', 1='E', 2='G'.
DB 0XCB
RLCA ; double the value and set flags.
JR Z,L18F3 ; to OUT-C-1 if still zero ('KLC').
ADD A,$43 ; add 'C' - will become 'E' if originally 1
; or 'G' if originally 2.
JR L1909 ; forward to OUT-C-2 to print.
; ---
; If mode was zero then, while printing a BASIC line, bit 2 of flags has been
; set if 'THEN' or ':' was encountered as a main character and reset otherwise.
; This is now used to determine if the 'K' cursor is to be printed but this
; transient state is also now transferred permanently to bit 3 of FLAGS
; to let the interrupt routine know how to decode the next key.
;; OUT-C-1
L18F3: LD HL,$5C3B ; Address FLAGS
RES 3,(HL) ; signal 'K' mode initially.
LD A,$4B ; prepare letter 'K'.
BIT 2,(HL) ; test FLAGS - was the
; previous main character ':' or 'THEN' ?
JR Z,L1909 ; forward to OUT-C-2 if so to print.
SET 3,(HL) ; signal 'L' mode to interrupt routine.
; Note. transient bit has been made permanent.
INC A ; augment from 'K' to 'L'.
BIT 3,(IY+$30) ; test FLAGS2 - consider caps lock ?
; which is maintained by KEY-INPUT.
JR Z,L1909 ; forward to OUT-C-2 if not set to print.
LD A,$43 ; alter 'L' to 'C'.
;; OUT-C-2
L1909: PUSH DE ; save address pointer but OK as OUT-FLASH
; uses alternate set without RST 10.
CALL L18C1 ; routine OUT-FLASH to print.
POP DE ; restore and
RET ; return.
; ----------------------------
; Get line number of next line
; ----------------------------
; These two subroutines are called while editing.
; This entry point is from ED-DOWN with HL addressing E_PPC
; to fetch the next line number.
; Also from AUTO-LIST with HL addressing S_TOP just to update S_TOP
; with the value of the next line number. It gets fetched but is discarded.
; These routines never get called while the editor is being used for input.
;; LN-FETCH
L190F: LD E,(HL) ; fetch low byte
INC HL ; address next
LD D,(HL) ; fetch high byte.
PUSH HL ; save system variable hi pointer.
EX DE,HL ; line number to HL,
INC HL ; increment as a starting point.
CALL L196E ; routine LINE-ADDR gets address in HL.
CALL L1695 ; routine LINE-NO gets line number in DE.
POP HL ; restore system variable hi pointer.
; This entry point is from the ED-UP with HL addressing E_PPC_hi
;; LN-STORE
L191C: BIT 5,(IY+$37) ; test FLAGX - input mode ?
RET NZ ; return if so.
; Note. above already checked by ED-UP/ED-DOWN.
LD (HL),D ; save high byte of line number.
DEC HL ; address lower
LD (HL),E ; save low byte of line number.
RET ; return.
; -----------------------------------------
; Outputting numbers at start of BASIC line
; -----------------------------------------
; This routine entered at OUT-SP-NO is used to compute then output the first
; three digits of a 4-digit BASIC line printing a space if necessary.
; The line number, or residual part, is held in HL and the BC register
; holds a subtraction value -1000, -100 or -10.
; Note. for example line number 200 -
; space(out_char), 2(out_code), 0(out_char) final number always out-code.
;; OUT-SP-2
L1925: LD A,E ; will be space if OUT-CODE not yet called.
; or $FF if spaces are suppressed.
; else $30 ('0').
; (from the first instruction at OUT-CODE)
; this guy is just too clever.
AND A ; test bit 7 of A.
RET M ; return if $FF, as leading spaces not
; required. This is set when printing line
; number and statement in MAIN-5.
JR L1937 ; forward to exit via OUT-CHAR.
; ---
; -> the single entry point.
;; OUT-SP-NO
L192A: XOR A ; initialize digit to 0
;; OUT-SP-1
L192B: ADD HL,BC ; add negative number to HL.
INC A ; increment digit
JR C,L192B ; back to OUT-SP-1 until no carry from
; the addition.
SBC HL,BC ; cancel the last addition
DEC A ; and decrement the digit.
JR Z,L1925 ; back to OUT-SP-2 if it is zero.
JP L15EF ; jump back to exit via OUT-CODE. ->
; -------------------------------------
; Outputting characters in a BASIC line
; -------------------------------------
; This subroutine ...
;; OUT-CHAR
L1937: CALL L2D1B ; routine NUMERIC tests if it is a digit ?
JR NC,L196C ; to OUT-CH-3 to print digit without
; changing mode. Will be 'K' mode if digits
; are at beginning of edit line.
CP $21 ; less than quote character ?
JR C,L196C ; to OUT-CH-3 to output controls and space.
RES 2,(IY+$01) ; initialize FLAGS to 'K' mode and leave
; unchanged if this character would precede
; a keyword.
CP $CB ; is character 'THEN' token ?
JR Z,L196C ; to OUT-CH-3 to output if so.
CP $3A ; is it ':' ?
JR NZ,L195A ; to OUT-CH-1 if not statement separator
; to change mode back to 'L'.
BIT 5,(IY+$37) ; FLAGX - Input Mode ??
JR NZ,L1968 ; to OUT-CH-2 if in input as no statements.
; Note. this check should seemingly be at
; the start. Commands seem inappropriate in
; INPUT mode and are rejected by the syntax
; checker anyway.
; unless INPUT LINE is being used.
BIT 2,(IY+$30) ; test FLAGS2 - is the ':' within quotes ?
JR Z,L196C ; to OUT-CH-3 if ':' is outside quoted text.
JR L1968 ; to OUT-CH-2 as ':' is within quotes
; ---
;; OUT-CH-1
L195A: CP $22 ; is it quote character '"' ?
JR NZ,L1968 ; to OUT-CH-2 with others to set 'L' mode.
PUSH AF ; save character.
LD A,($5C6A) ; fetch FLAGS2.
XOR $04 ; toggle the quotes flag.
LD ($5C6A),A ; update FLAGS2
POP AF ; and restore character.
;; OUT-CH-2
L1968: SET 2,(IY+$01) ; update FLAGS - signal L mode if the cursor
; is next.
;; OUT-CH-3
L196C: RST 10H ; PRINT-A vectors the character to
; channel 'S', 'K', 'R' or 'P'.
RET ; return.
; -------------------------------------------
; Get starting address of line, or line after
; -------------------------------------------
; This routine is used often to get the address, in HL, of a BASIC line
; number supplied in HL, or failing that the address of the following line
; and the address of the previous line in DE.
;; LINE-ADDR
L196E: PUSH HL ; save line number in HL register
LD HL,($5C53) ; fetch start of program from PROG
LD D,H ; transfer address to
LD E,L ; the DE register pair.
;; LINE-AD-1
L1974: POP BC ; restore the line number to BC
CALL L1980 ; routine CP-LINES compares with that
; addressed by HL
RET NC ; return if line has been passed or matched.
; if NZ, address of previous is in DE
PUSH BC ; save the current line number
CALL L19B8 ; routine NEXT-ONE finds address of next
; line number in DE, previous in HL.
EX DE,HL ; switch so next in HL
JR L1974 ; back to LINE-AD-1 for another comparison
; --------------------
; Compare line numbers
; --------------------
; This routine compares a line number supplied in BC with an addressed
; line number pointed to by HL.
;; CP-LINES
L1980: LD A,(HL) ; Load the high byte of line number and
CP B ; compare with that of supplied line number.
RET NZ ; return if yet to match (carry will be set).
INC HL ; address low byte of
LD A,(HL) ; number and pick up in A.
DEC HL ; step back to first position.
CP C ; now compare.
RET ; zero set if exact match.
; carry set if yet to match.
; no carry indicates a match or
; next available BASIC line or
; program end marker.
; -------------------
; Find each statement
; -------------------
; The single entry point EACH-STMT is used to
; 1) To find the D'th statement in a line.
; 2) To find a token in held E.
;; not-used
L1988: INC HL ;
INC HL ;
INC HL ;
; -> entry point.
;; EACH-STMT
L198B: LD ($5C5D),HL ; save HL in CH_ADD
LD C,$00 ; initialize quotes flag
;; EACH-S-1
L1990: DEC D ; decrease statement count
RET Z ; return if zero
RST 20H ; NEXT-CHAR
CP E ; is it the search token ?
JR NZ,L199A ; forward to EACH-S-3 if not
AND A ; clear carry
RET ; return signalling success.
; ---
;; EACH-S-2
L1998: INC HL ; next address
LD A,(HL) ; next character
;; EACH-S-3
L199A: CALL L18B6 ; routine NUMBER skips if number marker
LD ($5C5D),HL ; save in CH_ADD
CP $22 ; is it quotes '"' ?
JR NZ,L19A5 ; to EACH-S-4 if not
DEC C ; toggle bit 0 of C
;; EACH-S-4
L19A5: CP $3A ; is it ':'
JR Z,L19AD ; to EACH-S-5
CP $CB ; 'THEN'
JR NZ,L19B1 ; to EACH-S-6
;; EACH-S-5
L19AD: BIT 0,C ; is it in quotes
JR Z,L1990 ; to EACH-S-1 if not
;; EACH-S-6
L19B1: CP $0D ; end of line ?
JR NZ,L1998 ; to EACH-S-2
DEC D ; decrease the statement counter
; which should be zero else
; 'Statement Lost'.
SCF ; set carry flag - not found
RET ; return
; -----------------------------------------------------------------------
; Storage of variables. For full details - see chapter 24.
; ZX Spectrum BASIC Programming by Steven Vickers 1982.
; It is bits 7-5 of the first character of a variable that allow
; the six types to be distinguished. Bits 4-0 are the reduced letter.
; So any variable name is higher that $3F and can be distinguished
; also from the variables area end-marker $80.
;
; 76543210 meaning brief outline of format.
; -------- ------------------------ -----------------------
; 010 string variable. 2 byte length + contents.
; 110 string array. 2 byte length + contents.
; 100 array of numbers. 2 byte length + contents.
; 011 simple numeric variable. 5 bytes.
; 101 variable length named numeric. 5 bytes.
; 111 for-next loop variable. 18 bytes.
; 10000000 the variables area end-marker.
;
; Note. any of the above seven will serve as a program end-marker.
;
; -----------------------------------------------------------------------
; ------------
; Get next one
; ------------
; This versatile routine is used to find the address of the next line
; in the program area or the next variable in the variables area.
; The reason one routine is made to handle two apparently unrelated tasks
; is that it can be called indiscriminately when merging a line or a
; variable.
;; NEXT-ONE
L19B8: PUSH HL ; save the pointer address.
LD A,(HL) ; get first byte.
CP $40 ; compare with upper limit for line numbers.
JR C,L19D5 ; forward to NEXT-O-3 if within BASIC area.
; the continuation here is for the next variable unless the supplied
; line number was erroneously over 16383. see RESTORE command.
BIT 5,A ; is it a string or an array variable ?
JR Z,L19D6 ; forward to NEXT-O-4 to compute length.
ADD A,A ; test bit 6 for single-character variables.
JP M,L19C7 ; forward to NEXT-O-1 if so
CCF ; clear the carry for long-named variables.
; it remains set for for-next loop variables.
;; NEXT-O-1
L19C7: LD BC,$0005 ; set BC to 5 for floating point number
JR NC,L19CE ; forward to NEXT-O-2 if not a for/next
; variable.
LD C,$12 ; set BC to eighteen locations.
; value, limit, step, line and statement.
; now deal with long-named variables
;; NEXT-O-2
L19CE: RLA ; test if character inverted. carry will also
; be set for single character variables
INC HL ; address next location.
LD A,(HL) ; and load character.
JR NC,L19CE ; back to NEXT-O-2 if not inverted bit.
; forward immediately with single character
; variable names.
JR L19DB ; forward to NEXT-O-5 to add length of
; floating point number(s etc.).
; ---
; this branch is for line numbers.
;; NEXT-O-3
L19D5: INC HL ; increment pointer to low byte of line no.
; strings and arrays rejoin here
;; NEXT-O-4
L19D6: INC HL ; increment to address the length low byte.
LD C,(HL) ; transfer to C and
INC HL ; point to high byte of length.
LD B,(HL) ; transfer that to B
INC HL ; point to start of BASIC/variable contents.
; the three types of numeric variables rejoin here
;; NEXT-O-5
L19DB: ADD HL,BC ; add the length to give address of next
; line/variable in HL.
POP DE ; restore previous address to DE.
; ------------------
; Difference routine
; ------------------
; This routine terminates the above routine and is also called from the
; start of the next routine to calculate the length to reclaim.
;; DIFFER
L19DD: AND A ; prepare for true subtraction.
SBC HL,DE ; subtract the two pointers.
LD B,H ; transfer result
LD C,L ; to BC register pair.
ADD HL,DE ; add back
EX DE,HL ; and switch pointers
RET ; return values are the length of area in BC,
; low pointer (previous) in HL,
; high pointer (next) in DE.
; -----------------------
; Handle reclaiming space
; -----------------------
;
;; RECLAIM-1
L19E5: CALL L19DD ; routine DIFFER immediately above
;; RECLAIM-2
L19E8: PUSH BC ;
LD A,B ;
CPL ;
LD B,A ;
LD A,C ;
CPL ;
LD C,A ;
INC BC ;
CALL L1664 ; routine POINTERS
EX DE,HL ;
POP HL ;
ADD HL,DE ;
PUSH DE ;
LDIR ; copy bytes
POP HL ;
RET ;
; ----------------------------------------
; Read line number of line in editing area
; ----------------------------------------
; This routine reads a line number in the editing area returning the number
; in the BC register or zero if no digits exist before commands.
; It is called from LINE-SCAN to check the syntax of the digits.
; It is called from MAIN-3 to extract the line number in preparation for
; inclusion of the line in the BASIC program area.
;
; Interestingly the calculator stack is moved from its normal place at the
; end of dynamic memory to an adequate area within the system variables area.
; This ensures that in a low memory situation, that valid line numbers can
; be extracted without raising an error and that memory can be reclaimed
; by deleting lines. If the stack was in its normal place then a situation
; arises whereby the Spectrum becomes locked with no means of reclaiming space.
;; E-LINE-NO
L19FB: LD HL,($5C59) ; load HL from system variable E_LINE.
DEC HL ; decrease so that NEXT_CHAR can be used
; without skipping the first digit.
LD ($5C5D),HL ; store in the system variable CH_ADD.
RST 20H ; NEXT-CHAR skips any noise and white-space
; to point exactly at the first digit.
LD HL,$5C92 ; use MEM-0 as a temporary calculator stack
; an overhead of three locations are needed.
LD ($5C65),HL ; set new STKEND.
CALL L2D3B ; routine INT-TO-FP will read digits till
; a non-digit found.
CALL L2DA2 ; routine FP-TO-BC will retrieve number
; from stack at membot.
JR C,L1A15 ; forward to E-L-1 if overflow i.e. > 65535.
; 'Nonsense in BASIC'
LD HL,$D8F0 ; load HL with value -9999
ADD HL,BC ; add to line number in BC
;; E-L-1
L1A15: JP C,L1C8A ; to REPORT-C 'Nonsense in BASIC' if over.
; Note. As ERR_SP points to ED_ERROR
; the report is never produced although
; the RST $08 will update X_PTR leading to
; the error marker being displayed when
; the ED_LOOP is reiterated.
; in fact, since it is immediately
; cancelled, any report will do.
; a line in the range 0 - 9999 has been entered.
JP L16C5 ; jump back to SET-STK to set the calculator
; stack back to its normal place and exit
; from there.
; ---------------------------------
; Report and line number outputting
; ---------------------------------
; Entry point OUT-NUM-1 is used by the Error Reporting code to print
; the line number and later the statement number held in BC.
; If the statement was part of a direct command then -2 is used as a
; dummy line number so that zero will be printed in the report.
; This routine is also used to print the exponent of E-format numbers.
;
; Entry point OUT-NUM-2 is used from OUT-LINE to output the line number
; addressed by HL with leading spaces if necessary.
;; OUT-NUM-1
L1A1B: PUSH DE ; save the
PUSH HL ; registers.
XOR A ; set A to zero.
BIT 7,B ; is the line number minus two ?
JR NZ,L1A42 ; forward to OUT-NUM-4 if so to print zero
; for a direct command.
LD H,B ; transfer the
LD L,C ; number to HL.
LD E,$FF ; signal 'no leading zeros'.
JR L1A30 ; forward to continue at OUT-NUM-3
; ---
; from OUT-LINE - HL addresses line number.
;; OUT-NUM-2
L1A28: PUSH DE ; save flags
LD D,(HL) ; high byte to D
INC HL ; address next
LD E,(HL) ; low byte to E
PUSH HL ; save pointer
EX DE,HL ; transfer number to HL
LD E,$20 ; signal 'output leading spaces'
;; OUT-NUM-3
L1A30: LD BC,$FC18 ; value -1000
CALL L192A ; routine OUT-SP-NO outputs space or number
LD BC,$FF9C ; value -100
CALL L192A ; routine OUT-SP-NO
LD C,$F6 ; value -10 ( B is still $FF )
CALL L192A ; routine OUT-SP-NO
LD A,L ; remainder to A.
;; OUT-NUM-4
L1A42: CALL L15EF ; routine OUT-CODE for final digit.
; else report code zero wouldn't get
; printed.
POP HL ; restore the
POP DE ; registers and
RET ; return.
;***************************************************
;** Part 7. BASIC LINE AND COMMAND INTERPRETATION **
;***************************************************
; ----------------
; The offset table
; ----------------
; The BASIC interpreter has found a command code $CE - $FF
; which is then reduced to range $00 - $31 and added to the base address
; of this table to give the address of an offset which, when added to
; the offset therein, gives the location in the following parameter table
; where a list of class codes, separators and addresses relevant to the
; command exists.
;; offst-tbl
L1A48: DB L1AF9 - $ ; B1 offset to Address: P-DEF-FN
DB L1B14 - $ ; CB offset to Address: P-CAT
DB L1B06 - $ ; BC offset to Address: P-FORMAT
DB L1B0A - $ ; BF offset to Address: P-MOVE
DB L1B10 - $ ; C4 offset to Address: P-ERASE
DB L1AFC - $ ; AF offset to Address: P-OPEN
DB L1B02 - $ ; B4 offset to Address: P-CLOSE
DB L1AE2 - $ ; 93 offset to Address: P-MERGE
DB L1AE1 - $ ; 91 offset to Address: P-VERIFY
DB L1AE3 - $ ; 92 offset to Address: P-BEEP
DB L1AE7 - $ ; 95 offset to Address: P-CIRCLE
DB L1AEB - $ ; 98 offset to Address: P-INK
DB L1AEC - $ ; 98 offset to Address: P-PAPER
DB L1AED - $ ; 98 offset to Address: P-FLASH
DB L1AEE - $ ; 98 offset to Address: P-BRIGHT
DB L1AEF - $ ; 98 offset to Address: P-INVERSE
DB L1AF0 - $ ; 98 offset to Address: P-OVER
DB L1AF1 - $ ; 98 offset to Address: P-OUT
DB L1AD9 - $ ; 7F offset to Address: P-LPRINT
DB L1ADC - $ ; 81 offset to Address: P-LLIST
DB L1A8A - $ ; 2E offset to Address: P-STOP
DB L1AC9 - $ ; 6C offset to Address: P-READ
DB L1ACC - $ ; 6E offset to Address: P-DATA
DB L1ACF - $ ; 70 offset to Address: P-RESTORE
DB L1AA8 - $ ; 48 offset to Address: P-NEW
DB L1AF5 - $ ; 94 offset to Address: P-BORDER
DB L1AB8 - $ ; 56 offset to Address: P-CONT
DB L1AA2 - $ ; 3F offset to Address: P-DIM
DB L1AA5 - $ ; 41 offset to Address: P-REM
DB L1A90 - $ ; 2B offset to Address: P-FOR
DB L1A7D - $ ; 17 offset to Address: P-GO-TO
DB L1A86 - $ ; 1F offset to Address: P-GO-SUB
DB L1A9F - $ ; 37 offset to Address: P-INPUT
DB L1AE0 - $ ; 77 offset to Address: P-LOAD
DB L1AAE - $ ; 44 offset to Address: P-LIST
DB L1A7A - $ ; 0F offset to Address: P-LET
DB L1AC5 - $ ; 59 offset to Address: P-PAUSE
DB L1A98 - $ ; 2B offset to Address: P-NEXT
DB L1AB1 - $ ; 43 offset to Address: P-POKE
DB L1A9C - $ ; 2D offset to Address: P-PRINT
DB L1AC1 - $ ; 51 offset to Address: P-PLOT
DB L1AAB - $ ; 3A offset to Address: P-RUN
DB L1ADF - $ ; 6D offset to Address: P-SAVE
DB L1AB5 - $ ; 42 offset to Address: P-RANDOM
DB L1A81 - $ ; 0D offset to Address: P-IF
DB L1ABE - $ ; 49 offset to Address: P-CLS
DB L1AD2 - $ ; 5C offset to Address: P-DRAW
DB L1ABB - $ ; 44 offset to Address: P-CLEAR
DB L1A8D - $ ; 15 offset to Address: P-RETURN
DB L1AD6 - $ ; 5D offset to Address: P-COPY
; -------------------------------
; The parameter or "Syntax" table
; -------------------------------
; For each command there exists a variable list of parameters.
; If the character is greater than a space it is a required separator.
; If less, then it is a command class in the range 00 - 0B.
; Note that classes 00, 03 and 05 will fetch the addresses from this table.
; Some classes e.g. 07 and 0B have the same address in all invocations
; and the command is re-computed from the low-byte of the parameter address.
; Some e.g. 02 are only called once so a call to the command is made from
; within the class routine rather than holding the address within the table.
; Some class routines check syntax entirely and some leave this task for the
; command itself.
; Others for example CIRCLE (x,y,z) check the first part (x,y) using the
; class routine and the final part (,z) within the command.
; The last few commands appear to have been added in a rush but their syntax
; is rather simple e.g. MOVE "M1","M2"
;; P-LET
L1A7A: DB $01 ; Class-01 - A variable is required.
DB $3D ; Separator: '='
DB $02 ; Class-02 - An expression, numeric or string,
; must follow.
;; P-GO-TO
L1A7D: DB $06 ; Class-06 - A numeric expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1E67 ; Address: $1E67; Address: GO-TO
;; P-IF
L1A81: DB $06 ; Class-06 - A numeric expression must follow.
DB $CB ; Separator: 'THEN'
DB $05 ; Class-05 - Variable syntax checked
; by routine.
DEFW L1CF0 ; Address: $1CF0; Address: IF
;; P-GO-SUB
L1A86: DB $06 ; Class-06 - A numeric expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1EED ; Address: $1EED; Address: GO-SUB
;; P-STOP
L1A8A: DB $00 ; Class-00 - No further operands.
DEFW L1CEE ; Address: $1CEE; Address: STOP
;; P-RETURN
L1A8D: DB $00 ; Class-00 - No further operands.
DEFW L1F23 ; Address: $1F23; Address: RETURN
;; P-FOR
L1A90: DB $04 ; Class-04 - A single character variable must
; follow.
DB $3D ; Separator: '='
DB $06 ; Class-06 - A numeric expression must follow.
DB $CC ; Separator: 'TO'
DB $06 ; Class-06 - A numeric expression must follow.
DB $05 ; Class-05 - Variable syntax checked
; by routine.
DEFW L1D03 ; Address: $1D03; Address: FOR
;; P-NEXT
L1A98: DB $04 ; Class-04 - A single character variable must
; follow.
DB $00 ; Class-00 - No further operands.
DEFW L1DAB ; Address: $1DAB; Address: NEXT
;; P-PRINT
L1A9C: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1FCD ; Address: $1FCD; Address: PRINT
;; P-INPUT
L1A9F: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L2089 ; Address: $2089; Address: INPUT
;; P-DIM
L1AA2: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L2C02 ; Address: $2C02; Address: DIM
;; P-REM
L1AA5: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1BB2 ; Address: $1BB2; Address: REM
;; P-NEW
L1AA8: DB $00 ; Class-00 - No further operands.
DEFW L11B7 ; Address: $11B7; Address: NEW
;; P-RUN
L1AAB: DB $03 ; Class-03 - A numeric expression may follow
; else default to zero.
DEFW L1EA1 ; Address: $1EA1; Address: RUN
;; P-LIST
L1AAE: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L17F9 ; Address: $17F9; Address: LIST
;; P-POKE
L1AB1: DB $08 ; Class-08 - Two comma-separated numeric
; expressions required.
DB $00 ; Class-00 - No further operands.
DEFW L1E80 ; Address: $1E80; Address: POKE
;; P-RANDOM
L1AB5: DB $03 ; Class-03 - A numeric expression may follow
; else default to zero.
DEFW L1E4F ; Address: $1E4F; Address: RANDOMIZE
;; P-CONT
L1AB8: DB $00 ; Class-00 - No further operands.
DEFW L1E5F ; Address: $1E5F; Address: CONTINUE
;; P-CLEAR
L1ABB: DB $03 ; Class-03 - A numeric expression may follow
; else default to zero.
DEFW L1EAC ; Address: $1EAC; Address: CLEAR
;; P-CLS
L1ABE: DB $00 ; Class-00 - No further operands.
DEFW L0D6B ; Address: $0D6B; Address: CLS
;; P-PLOT
L1AC1: DB $09 ; Class-09 - Two comma-separated numeric
; expressions required with optional colour
; items.
DB $00 ; Class-00 - No further operands.
DEFW L22DC ; Address: $22DC; Address: PLOT
;; P-PAUSE
L1AC5: DB $06 ; Class-06 - A numeric expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1F3A ; Address: $1F3A; Address: PAUSE
;; P-READ
L1AC9: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1DED ; Address: $1DED; Address: READ
;; P-DATA
L1ACC: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1E27 ; Address: $1E27; Address: DATA
;; P-RESTORE
L1ACF: DB $03 ; Class-03 - A numeric expression may follow
; else default to zero.
DEFW L1E42 ; Address: $1E42; Address: RESTORE
;; P-DRAW
L1AD2: DB $09 ; Class-09 - Two comma-separated numeric
; expressions required with optional colour
; items.
DB $05 ; Class-05 - Variable syntax checked
; by routine.
DEFW L2382 ; Address: $2382; Address: DRAW
;; P-COPY
L1AD6: DB $00 ; Class-00 - No further operands.
DEFW L0EAC ; Address: $0EAC; Address: COPY
;; P-LPRINT
L1AD9: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1FC9 ; Address: $1FC9; Address: LPRINT
;; P-LLIST
L1ADC: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L17F5 ; Address: $17F5; Address: LLIST
;; P-SAVE
L1ADF: DB $0B ; Class-0B - Offset address converted to tape
; command.
;; P-LOAD
L1AE0: DB $0B ; Class-0B - Offset address converted to tape
; command.
;; P-VERIFY
L1AE1: DB $0B ; Class-0B - Offset address converted to tape
; command.
;; P-MERGE
L1AE2: DB $0B ; Class-0B - Offset address converted to tape
; command.
;; P-BEEP
L1AE3: DB $08 ; Class-08 - Two comma-separated numeric
; expressions required.
DB $00 ; Class-00 - No further operands.
DEFW L03F8 ; Address: $03F8; Address: BEEP
;; P-CIRCLE
L1AE7: DB $09 ; Class-09 - Two comma-separated numeric
; expressions required with optional colour
; items.
DB $05 ; Class-05 - Variable syntax checked
; by routine.
DEFW L2320 ; Address: $2320; Address: CIRCLE
;; P-INK
L1AEB: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-PAPER
L1AEC: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-FLASH
L1AED: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-BRIGHT
L1AEE: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-INVERSE
L1AEF: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-OVER
L1AF0: DB $07 ; Class-07 - Offset address is converted to
; colour code.
;; P-OUT
L1AF1: DB $08 ; Class-08 - Two comma-separated numeric
; expressions required.
DB $00 ; Class-00 - No further operands.
DEFW L1E7A ; Address: $1E7A; Address: OUT
;; P-BORDER
L1AF5: DB $06 ; Class-06 - A numeric expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L2294 ; Address: $2294; Address: BORDER
;; P-DEF-FN
L1AF9: DB $05 ; Class-05 - Variable syntax checked entirely
; by routine.
DEFW L1F60 ; Address: $1F60; Address: DEF-FN
;; P-OPEN
L1AFC: DB $06 ; Class-06 - A numeric expression must follow.
DB $2C ; Separator: ',' see Footnote *
DB $0A ; Class-0A - A string expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1736 ; Address: $1736; Address: OPEN
;; P-CLOSE
L1B02: DB $06 ; Class-06 - A numeric expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L16E5 ; Address: $16E5; Address: CLOSE
;; P-FORMAT
L1B06: DB $0A ; Class-0A - A string expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1793 ; Address: $1793; Address: CAT-ETC
;; P-MOVE
L1B0A: DB $0A ; Class-0A - A string expression must follow.
DB $2C ; Separator: ','
DB $0A ; Class-0A - A string expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1793 ; Address: $1793; Address: CAT-ETC
;; P-ERASE
L1B10: DB $0A ; Class-0A - A string expression must follow.
DB $00 ; Class-00 - No further operands.
DEFW L1793 ; Address: $1793; Address: CAT-ETC
;; P-CAT
L1B14: DB $00 ; Class-00 - No further operands.
DEFW L1793 ; Address: $1793; Address: CAT-ETC
; * Note that a comma is required as a separator with the OPEN command
; but the Interface 1 programmers relaxed this allowing ';' as an
; alternative for their channels creating a confusing mixture of
; allowable syntax as it is this ROM which opens or re-opens the
; normal channels.
; -------------------------------
; Main parser (BASIC interpreter)
; -------------------------------
; This routine is called once from MAIN-2 when the BASIC line is to
; be entered or re-entered into the Program area and the syntax
; requires checking.
;; LINE-SCAN
L1B17: RES 7,(IY+$01) ; update FLAGS - signal checking syntax
CALL L19FB ; routine E-LINE-NO >>
; fetches the line number if in range.
XOR A ; clear the accumulator.
LD ($5C47),A ; set statement number SUBPPC to zero.
DEC A ; set accumulator to $FF.
LD ($5C3A),A ; set ERR_NR to 'OK' - 1.
JR L1B29 ; forward to continue at STMT-L-1.
; --------------
; Statement loop
; --------------
;
;
;; STMT-LOOP
L1B28: RST 20H ; NEXT-CHAR
; -> the entry point from above or LINE-RUN
;; STMT-L-1
L1B29: CALL L16BF ; routine SET-WORK clears workspace etc.
INC (IY+$0D) ; increment statement number SUBPPC
JP M,L1C8A ; to REPORT-C to raise
; 'Nonsense in BASIC' if over 127.
RST 18H ; GET-CHAR
LD B,$00 ; set B to zero for later indexing.
; early so any other reason ???
CP $0D ; is character carriage return ?
; i.e. an empty statement.
JR Z,L1BB3 ; forward to LINE-END if so.
CP $3A ; is it statement end marker ':' ?
; i.e. another type of empty statement.
JR Z,L1B28 ; back to STMT-LOOP if so.
LD HL,L1B76 ; address: STMT-RET
PUSH HL ; is now pushed as a return address
LD C,A ; transfer the current character to C.
; advance CH_ADD to a position after command and test if it is a command.
RST 20H ; NEXT-CHAR to advance pointer
LD A,C ; restore current character
SUB $CE ; subtract 'DEF FN' - first command
JP C,L1C8A ; jump to REPORT-C if less than a command
; raising
; 'Nonsense in BASIC'
LD C,A ; put the valid command code back in C.
; register B is zero.
LD HL,L1A48 ; address: offst-tbl
ADD HL,BC ; index into table with one of 50 commands.
LD C,(HL) ; pick up displacement to syntax table entry.
ADD HL,BC ; add to address the relevant entry.
JR L1B55 ; forward to continue at GET-PARAM
; ----------------------
; The main scanning loop
; ----------------------
; not documented properly
;
;; SCAN-LOOP
L1B52: LD HL,($5C74) ; fetch temporary address from T_ADDR
; during subsequent loops.
; -> the initial entry point with HL addressing start of syntax table entry.
;; GET-PARAM
L1B55: LD A,(HL) ; pick up the parameter.
INC HL ; address next one.
LD ($5C74),HL ; save pointer in system variable T_ADDR
LD BC,L1B52 ; address: SCAN-LOOP
PUSH BC ; is now pushed on stack as looping address.
LD C,A ; store parameter in C.
CP $20 ; is it greater than ' ' ?
JR NC,L1B6F ; forward to SEPARATOR to check that correct
; separator appears in statement if so.
LD HL,L1C01 ; address: class-tbl.
LD B,$00 ; prepare to index into the class table.
ADD HL,BC ; index to find displacement to routine.
LD C,(HL) ; displacement to BC
ADD HL,BC ; add to address the CLASS routine.
PUSH HL ; push the address on the stack.
RST 18H ; GET-CHAR - HL points to place in statement.
DEC B ; reset the zero flag - the initial state
; for all class routines.
RET ; and make an indirect jump to routine
; and then SCAN-LOOP (also on stack).
; Note. one of the class routines will eventually drop the return address
; off the stack breaking out of the above seemingly endless loop.
; ----------------
; Verify separator
; ----------------
; This routine is called once to verify that the mandatory separator
; present in the parameter table is also present in the correct
; location following the command. For example, the 'THEN' token after
; the 'IF' token and expression.
;; SEPARATOR
L1B6F: RST 18H ; GET-CHAR
CP C ; does it match the character in C ?
JP NZ,L1C8A ; jump forward to REPORT-C if not
; 'Nonsense in BASIC'.
RST 20H ; NEXT-CHAR advance to next character
RET ; return.
; ------------------------------
; Come here after interpretation
; ------------------------------
;
;
;; STMT-RET
L1B76: CALL L1F54 ; routine BREAK-KEY is tested after every
; statement.
JR C,L1B7D ; step forward to STMT-R-1 if not pressed.
;; REPORT-L
L1B7B: RST 08H ; ERROR-1
DB $14 ; Error Report: BREAK into program
;; STMT-R-1
L1B7D IF BAS48_ONLY=1
BIT 7,(IY+0X0A)
ELSE
CALL L3B4D ; Spectrum 128 patch
NOP
ENDIF
L1B81: JR NZ,L1BF4 ; forward to STMT-NEXT if a program line.
LD HL,($5C42) ; fetch line number from NEWPPC
BIT 7,H ; will be set if minus two - direct command(s)
JR Z,L1B9E ; forward to LINE-NEW if a jump is to be
; made to a new program line/statement.
; --------------------
; Run a direct command
; --------------------
; A direct command is to be run or, if continuing from above,
; the next statement of a direct command is to be considered.
;; LINE-RUN
L1B8A: LD HL,$FFFE ; The dummy value minus two
LD ($5C45),HL ; is set/reset as line number in PPC.
LD HL,($5C61) ; point to end of line + 1 - WORKSP.
DEC HL ; now point to $80 end-marker.
LD DE,($5C59) ; address the start of line E_LINE.
DEC DE ; now location before - for GET-CHAR.
LD A,($5C44) ; load statement to A from NSPPC.
JR L1BD1 ; forward to NEXT-LINE.
; ------------------------------
; Find start address of new line
; ------------------------------
; The branch was to here if a jump is to made to a new line number
; and statement.
; That is the previous statement was a GO TO, GO SUB, RUN, RETURN, NEXT etc..
;; LINE-NEW
L1B9E: CALL L196E ; routine LINE-ADDR gets address of line
; returning zero flag set if line found.
LD A,($5C44) ; fetch new statement from NSPPC
JR Z,L1BBF ; forward to LINE-USE if line matched.
; continue as must be a direct command.
AND A ; test statement which should be zero
JR NZ,L1BEC ; forward to REPORT-N if not.
; 'Statement lost'
;
LD B,A ; save statement in B. ?
LD A,(HL) ; fetch high byte of line number.
AND $C0 ; test if using direct command
; a program line is less than $3F
LD A,B ; retrieve statement.
; (we can assume it is zero).
JR Z,L1BBF ; forward to LINE-USE if was a program line
; Alternatively a direct statement has finished correctly.
;; REPORT-0
L1BB0: RST 08H ; ERROR-1
DB $FF ; Error Report: OK
; ------------------
; Handle REM command
; ------------------
; The REM command routine.
; The return address STMT-RET is dropped and the rest of line ignored.
;; REM
L1BB2: POP BC ; drop return address STMT-RET and
; continue ignoring rest of line.
; ------------
; End of line?
; ------------
;
;
;; LINE-END
L1BB3: CALL L2530 ; routine SYNTAX-Z (UNSTACK-Z?)
RET Z ; return if checking syntax.
LD HL,($5C55) ; fetch NXTLIN to HL.
LD A,$C0 ; test against the
AND (HL) ; system limit $3F.
RET NZ ; return if more as must be
; end of program.
; (or direct command)
XOR A ; set statement to zero.
; and continue to set up the next following line and then consider this new one.
; ---------------------
; General line checking
; ---------------------
; The branch was here from LINE-NEW if BASIC is branching.
; or a continuation from above if dealing with a new sequential line.
; First make statement zero number one leaving others unaffected.
;; LINE-USE
L1BBF: CP $01 ; will set carry if zero.
ADC A,$00 ; add in any carry.
LD D,(HL) ; high byte of line number to D.
INC HL ; advance pointer.
LD E,(HL) ; low byte of line number to E.
LD ($5C45),DE ; set system variable PPC.
INC HL ; advance pointer.
LD E,(HL) ; low byte of line length to E.
INC HL ; advance pointer.
LD D,(HL) ; high byte of line length to D.
EX DE,HL ; swap pointer to DE before
ADD HL,DE ; adding to address the end of line.
INC HL ; advance to start of next line.
; -----------------------------
; Update NEXT LINE but consider
; previous line or edit line.
; -----------------------------
; The pointer will be the next line if continuing from above or to
; edit line end-marker ($80) if from LINE-RUN.
;; NEXT-LINE
L1BD1: LD ($5C55),HL ; store pointer in system variable NXTLIN
EX DE,HL ; bring back pointer to previous or edit line
LD ($5C5D),HL ; and update CH_ADD with character address.
LD D,A ; store statement in D.
LD E,$00 ; set E to zero to suppress token searching
; if EACH-STMT is to be called.
LD (IY+$0A),$FF ; set statement NSPPC to $FF signalling
; no jump to be made.
DEC D ; decrement and test statement
LD (IY+$0D),D ; set SUBPPC to decremented statement number.
JP Z,L1B28 ; to STMT-LOOP if result zero as statement is
; at start of line and address is known.
INC D ; else restore statement.
CALL L198B ; routine EACH-STMT finds the D'th statement
; address as E does not contain a token.
JR Z,L1BF4 ; forward to STMT-NEXT if address found.
;; REPORT-N
L1BEC: RST 08H ; ERROR-1
DB $16 ; Error Report: Statement lost
; -----------------
; End of statement?
; -----------------
; This combination of routines is called from 20 places when
; the end of a statement should have been reached and all preceding
; syntax is in order.
;; CHECK-END
L1BEE: CALL L2530 ; routine SYNTAX-Z
RET NZ ; return immediately in runtime
POP BC ; drop address of calling routine.
POP BC ; drop address STMT-RET.
; and continue to find next statement.
; --------------------
; Go to next statement
; --------------------
; Acceptable characters at this point are carriage return and ':'.
; If so go to next statement which in the first case will be on next line.
;; STMT-NEXT
L1BF4 IF BAS48_ONLY=1
RST 0X18
CP 0X0D
ELSE
CALL L3B5D ; Spectrum 128 patch
ENDIF
L1BF7: JR Z,L1BB3 ; back to LINE-END if so.
CP $3A ; is it ':' ?
JP Z,L1B28 ; jump back to STMT-LOOP to consider
; further statements
JP L1C8A ; jump to REPORT-C with any other character
; 'Nonsense in BASIC'.
; Note. the two-byte sequence 'rst 08; DB $0b' could replace the above jp.
; -------------------
; Command class table
; -------------------
;
;; class-tbl
L1C01: DB L1C10 - $ ; 0F offset to Address: CLASS-00
DB L1C1F - $ ; 1D offset to Address: CLASS-01
DB L1C4E - $ ; 4B offset to Address: CLASS-02
DB L1C0D - $ ; 09 offset to Address: CLASS-03
DB L1C6C - $ ; 67 offset to Address: CLASS-04
DB L1C11 - $ ; 0B offset to Address: CLASS-05
DB L1C82 - $ ; 7B offset to Address: CLASS-06
DB L1C96 - $ ; 8E offset to Address: CLASS-07
DB L1C7A - $ ; 71 offset to Address: CLASS-08
DB L1CBE - $ ; B4 offset to Address: CLASS-09
DB L1C8C - $ ; 81 offset to Address: CLASS-0A
DB L1CDB - $ ; CF offset to Address: CLASS-0B
; --------------------------------
; Command classes---00, 03, and 05
; --------------------------------
; class-03 e.g RUN or RUN 200 ; optional operand
; class-00 e.g CONTINUE ; no operand
; class-05 e.g PRINT ; variable syntax checked by routine
;; CLASS-03
L1C0D: CALL L1CDE ; routine FETCH-NUM
;; CLASS-00
L1C10: CP A ; reset zero flag.
; if entering here then all class routines are entered with zero reset.
;; CLASS-05
L1C11: POP BC ; drop address SCAN-LOOP.
CALL Z,L1BEE ; if zero set then call routine CHECK-END >>>
; as should be no further characters.
EX DE,HL ; save HL to DE.
LD HL,($5C74) ; fetch T_ADDR
LD C,(HL) ; fetch low byte of routine
INC HL ; address next.
LD B,(HL) ; fetch high byte of routine.
EX DE,HL ; restore HL from DE
PUSH BC ; push the address
RET ; and make an indirect jump to the command.
; --------------------------------
; Command classes---01, 02, and 04
; --------------------------------
; class-01 e.g LET A = 2*3 ; a variable is reqd
; This class routine is also called from INPUT and READ to find the
; destination variable for an assignment.
;; CLASS-01
L1C1F: CALL L28B2 ; routine LOOK-VARS returns carry set if not
; found in runtime.
; ----------------------
; Variable in assignment
; ----------------------
;
;
;; VAR-A-1
L1C22: LD (IY+$37),$00 ; set FLAGX to zero
JR NC,L1C30 ; forward to VAR-A-2 if found or checking
; syntax.
SET 1,(IY+$37) ; FLAGX - Signal a new variable
JR NZ,L1C46 ; to VAR-A-3 if not assigning to an array
; e.g. LET a$(3,3) = "X"
;; REPORT-2
L1C2E: RST 08H ; ERROR-1
DB $01 ; Error Report: Variable not found
;; VAR-A-2
L1C30: CALL Z,L2996 ; routine STK-VAR considers a subscript/slice
BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ?
JR NZ,L1C46 ; to VAR-A-3 if numeric
XOR A ; default to array/slice - to be retained.
CALL L2530 ; routine SYNTAX-Z
CALL NZ,L2BF1 ; routine STK-FETCH is called in runtime
; may overwrite A with 1.
LD HL,$5C71 ; address system variable FLAGX
OR (HL) ; set bit 0 if simple variable to be reclaimed
LD (HL),A ; update FLAGX
EX DE,HL ; start of string/subscript to DE
;; VAR-A-3
L1C46: LD ($5C72),BC ; update STRLEN
LD ($5C4D),HL ; and DEST of assigned string.
RET ; return.
; -------------------------------------------------
; class-02 e.g. LET a = 1 + 1 ; an expression must follow
;; CLASS-02
L1C4E: POP BC ; drop return address SCAN-LOOP
CALL L1C56 ; routine VAL-FET-1 is called to check
; expression and assign result in runtime
CALL L1BEE ; routine CHECK-END checks nothing else
; is present in statement.
RET ; Return
; -------------
; Fetch a value
; -------------
;
;
;; VAL-FET-1
L1C56: LD A,($5C3B) ; initial FLAGS to A
;; VAL-FET-2
L1C59: PUSH AF ; save A briefly
CALL L24FB ; routine SCANNING evaluates expression.
POP AF ; restore A
LD D,(IY+$01) ; post-SCANNING FLAGS to D
XOR D ; xor the two sets of flags
AND $40 ; pick up bit 6 of xored FLAGS should be zero
JR NZ,L1C8A ; forward to REPORT-C if not zero
; 'Nonsense in BASIC' - results don't agree.
BIT 7,D ; test FLAGS - is syntax being checked ?
JP NZ,L2AFF ; jump forward to LET to make the assignment
; in runtime.
RET ; but return from here if checking syntax.
; ------------------
; Command class---04
; ------------------
; class-04 e.g. FOR i ; a single character variable must follow
;; CLASS-04
L1C6C: CALL L28B2 ; routine LOOK-VARS
PUSH AF ; preserve flags.
LD A,C ; fetch type - should be 011xxxxx
OR $9F ; combine with 10011111.
INC A ; test if now $FF by incrementing.
JR NZ,L1C8A ; forward to REPORT-C if result not zero.
POP AF ; else restore flags.
JR L1C22 ; back to VAR-A-1
; --------------------------------
; Expect numeric/string expression
; --------------------------------
; This routine is used to get the two coordinates of STRING$, ATTR and POINT.
; It is also called from PRINT-ITEM to get the two numeric expressions that
; follow the AT ( in PRINT AT, INPUT AT).
;; NEXT-2NUM
L1C79: RST 20H ; NEXT-CHAR advance past 'AT' or '('.
; --------
; class-08 e.g POKE 65535,2 ; two numeric expressions separated by comma
;; CLASS-08
;; EXPT-2NUM
L1C7A: CALL L1C82 ; routine EXPT-1NUM is called for first
; numeric expression
CP $2C ; is character ',' ?
JR NZ,L1C8A ; to REPORT-C if not required separator.
; 'Nonsense in BASIC'.
RST 20H ; NEXT-CHAR
; ->
; class-06 e.g. GOTO a*1000 ; a numeric expression must follow
;; CLASS-06
;; EXPT-1NUM
L1C82: CALL L24FB ; routine SCANNING
BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ?
RET NZ ; return if result is numeric.
;; REPORT-C
L1C8A: RST 08H ; ERROR-1
DB $0B ; Error Report: Nonsense in BASIC
; ---------------------------------------------------------------
; class-0A e.g. ERASE "????" ; a string expression must follow.
; ; these only occur in unimplemented commands
; ; although the routine expt-exp is called
; ; from SAVE-ETC
;; CLASS-0A
;; EXPT-EXP
L1C8C: CALL L24FB ; routine SCANNING
BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ?
RET Z ; return if string result.
JR L1C8A ; back to REPORT-C if numeric.
; ---------------------
; Set permanent colours
; class 07
; ---------------------
; class-07 e.g PAPER 6 ; a single class for a collection of
; ; similar commands. Clever.
;
; Note. these commands should ensure that current channel is 'S'
;; CLASS-07
L1C96: BIT 7,(IY+$01) ; test FLAGS - checking syntax only ?
RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use
CALL NZ,L0D4D ; routine TEMPS is called in runtime.
POP AF ; drop return address SCAN-LOOP
LD A,($5C74) ; T_ADDR_lo to accumulator.
; points to '$07' entry + 1
; e.g. for INK points to $EC now
; Note if you move alter the syntax table next line may have to be altered.
; Note. For ZASM assembler replace following expression with SUB $13.
L1CA5 SUB LOW (L1AEB)-$D8 ; % 256 ; convert $EB to $D8 ('INK') etc.
; ( is SUB $13 in standard ROM )
CALL L21FC ; routine CO-TEMP-4
CALL L1BEE ; routine CHECK-END check that nothing else
; in statement.
; return here in runtime.
LD HL,($5C8F) ; pick up ATTR_T and MASK_T
LD ($5C8D),HL ; and store in ATTR_P and MASK_P
LD HL,$5C91 ; point to P_FLAG.
LD A,(HL) ; pick up in A
RLCA ; rotate to left
XOR (HL) ; combine with HL
AND $AA ; 10101010
XOR (HL) ; only permanent bits affected
LD (HL),A ; reload into P_FLAG.
RET ; return.
; ------------------
; Command class---09
; ------------------
; e.g. PLOT PAPER 0; 128,88 ; two coordinates preceded by optional
; ; embedded colour items.
;
; Note. this command should ensure that current channel is actually 'S'.
;; CLASS-09
L1CBE: CALL L2530 ; routine SYNTAX-Z
JR Z,L1CD6 ; forward to CL-09-1 if checking syntax.
RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use
CALL L0D4D ; routine TEMPS is called.
LD HL,$5C90 ; point to MASK_T
LD A,(HL) ; fetch mask to accumulator.
OR $F8 ; or with 11111000 paper/bright/flash 8
LD (HL),A ; mask back to MASK_T system variable.
RES 6,(IY+$57) ; reset P_FLAG - signal NOT PAPER 9 ?
RST 18H ; GET-CHAR
;; CL-09-1
L1CD6: CALL L21E2 ; routine CO-TEMP-2 deals with any embedded
; colour items.
JR L1C7A ; exit via EXPT-2NUM to check for x,y.
; Note. if either of the numeric expressions contain STR$ then the flag setting
; above will be undone when the channel flags are reset during STR$.
; e.g.
; 10 BORDER 3 : PLOT VAL STR$ 128, VAL STR$ 100
; credit John Elliott.
; ------------------
; Command class---0B
; ------------------
; Again a single class for four commands.
; This command just jumps back to SAVE-ETC to handle the four tape commands.
; The routine itself works out which command has called it by examining the
; address in T_ADDR_lo. Note therefore that the syntax table has to be
; located where these and other sequential command addresses are not split
; over a page boundary.
;; CLASS-0B
L1CDB: JP L0605 ; jump way back to SAVE-ETC
; --------------
; Fetch a number
; --------------
; This routine is called from CLASS-03 when a command may be followed by
; an optional numeric expression e.g. RUN. If the end of statement has
; been reached then zero is used as the default.
; Also called from LIST-4.
;; FETCH-NUM
L1CDE: CP $0D ; is character a carriage return ?
JR Z,L1CE6 ; forward to USE-ZERO if so
CP $3A ; is it ':' ?
JR NZ,L1C82 ; forward to EXPT-1NUM if not.
; else continue and use zero.
; ----------------
; Use zero routine
; ----------------
; This routine is called four times to place the value zero on the
; calculator stack as a default value in runtime.
;; USE-ZERO
L1CE6: CALL L2530 ; routine SYNTAX-Z (UNSTACK-Z?)
RET Z ;
RST 28H ;; FP-CALC
DB $A0 ;;stk-zero ;0.
DB $38 ;;end-calc
RET ; return.
; -------------------
; Handle STOP command
; -------------------
; Command Syntax: STOP
; One of the shortest and least used commands. As with 'OK' not an error.
;; REPORT-9
;; STOP
L1CEE: RST 08H ; ERROR-1
DB $08 ; Error Report: STOP statement
; -----------------
; Handle IF command
; -----------------
; e.g. IF score>100 THEN PRINT "You Win"
; The parser has already checked the expression the result of which is on
; the calculator stack. The presence of the 'THEN' separator has also been
; checked and CH-ADD points to the command after THEN.
;
;; IF
L1CF0: POP BC ; drop return address - STMT-RET
CALL L2530 ; routine SYNTAX-Z
JR Z,L1D00 ; forward to IF-1 if checking syntax
; to check syntax of PRINT "You Win"
RST 28H ;; FP-CALC score>100 (1=TRUE 0=FALSE)
DB $02 ;;delete .
DB $38 ;;end-calc
EX DE,HL ; make HL point to deleted value
CALL L34E9 ; routine TEST-ZERO
JP C,L1BB3 ; jump to LINE-END if FALSE (0)
;; IF-1
L1D00: JP L1B29 ; to STMT-L-1, if true (1) to execute command
; after 'THEN' token.
; ------------------
; Handle FOR command
; ------------------
; e.g. FOR i = 0 TO 1 STEP 0.1
; Using the syntax tables, the parser has already checked for a start and
; limit value and also for the intervening separator.
; the two values v,l are on the calculator stack.
; CLASS-04 has also checked the variable and the name is in STRLEN_lo.
; The routine begins by checking for an optional STEP.
;; FOR
L1D03: CP $CD ; is there a 'STEP' ?
JR NZ,L1D10 ; to F-USE-1 if not to use 1 as default.
RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM
CALL L1BEE ; routine CHECK-END
JR L1D16 ; to F-REORDER
; ---
;; F-USE-1
L1D10: CALL L1BEE ; routine CHECK-END
RST 28H ;; FP-CALC v,l.
DB $A1 ;;stk-one v,l,1=s.
DB $38 ;;end-calc
;; F-REORDER
L1D16: RST 28H ;; FP-CALC v,l,s.
DB $C0 ;;st-mem-0 v,l,s.
DB $02 ;;delete v,l.
DB $01 ;;exchange l,v.
DB $E0 ;;get-mem-0 l,v,s.
DB $01 ;;exchange l,s,v.
DB $38 ;;end-calc
CALL L2AFF ; routine LET assigns the initial value v to
; the variable altering type if necessary.
LD ($5C68),HL ; The system variable MEM is made to point to
; the variable instead of its normal
; location MEMBOT
DEC HL ; point to single-character name
LD A,(HL) ; fetch name
SET 7,(HL) ; set bit 7 at location
LD BC,$0006 ; add six to HL
ADD HL,BC ; to address where limit should be.
RLCA ; test bit 7 of original name.
JR C,L1D34 ; forward to F-L-S if already a FOR/NEXT
; variable
LD C,$0D ; otherwise an additional 13 bytes are needed.
; 5 for each value, two for line number and
; 1 byte for looping statement.
CALL L1655 ; routine MAKE-ROOM creates them.
INC HL ; make HL address limit.
;; F-L-S
L1D34: PUSH HL ; save position.
RST 28H ;; FP-CALC l,s.
DB $02 ;;delete l.
DB $02 ;;delete .
DB $38 ;;end-calc
; DE points to STKEND, l.
POP HL ; restore variable position
EX DE,HL ; swap pointers
LD C,$0A ; ten bytes to move
LDIR ; Copy 'deleted' values to variable.
LD HL,($5C45) ; Load with current line number from PPC
EX DE,HL ; exchange pointers.
LD (HL),E ; save the looping line
INC HL ; in the next
LD (HL),D ; two locations.
LD D,(IY+$0D) ; fetch statement from SUBPPC system variable.
INC D ; increment statement.
INC HL ; and pointer
LD (HL),D ; and store the looping statement.
;
CALL L1DDA ; routine NEXT-LOOP considers an initial
RET NC ; iteration. Return to STMT-RET if a loop is
; possible to execute next statement.
; no loop is possible so execution continues after the matching 'NEXT'
LD B,(IY+$38) ; get single-character name from STRLEN_lo
LD HL,($5C45) ; get the current line from PPC
LD ($5C42),HL ; and store it in NEWPPC
LD A,($5C47) ; fetch current statement from SUBPPC
NEG ; Negate as counter decrements from zero
; initially and we are in the middle of a
; line.
LD D,A ; Store result in D.
LD HL,($5C5D) ; get current address from CH_ADD
LD E,$F3 ; search will be for token 'NEXT'
;; F-LOOP
L1D64: PUSH BC ; save variable name.
LD BC,($5C55) ; fetch NXTLIN
CALL L1D86 ; routine LOOK-PROG searches for 'NEXT' token.
LD ($5C55),BC ; update NXTLIN
POP BC ; and fetch the letter
JR C,L1D84 ; forward to REPORT-I if the end of program
; was reached by LOOK-PROG.
; 'FOR without NEXT'
RST 20H ; NEXT-CHAR fetches character after NEXT
OR $20 ; ensure it is upper-case.
CP B ; compare with FOR variable name
JR Z,L1D7C ; forward to F-FOUND if it matches.
; but if no match i.e. nested FOR/NEXT loops then continue search.
RST 20H ; NEXT-CHAR
JR L1D64 ; back to F-LOOP
; ---
;; F-FOUND
L1D7C: RST 20H ; NEXT-CHAR
LD A,$01 ; subtract the negated counter from 1
SUB D ; to give the statement after the NEXT
LD ($5C44),A ; set system variable NSPPC
RET ; return to STMT-RET to branch to new
; line and statement. ->
; ---
;; REPORT-I
L1D84: RST 08H ; ERROR-1
DB $11 ; Error Report: FOR without NEXT
; ---------
; LOOK-PROG
; ---------
; Find DATA, DEF FN or NEXT.
; This routine searches the program area for one of the above three keywords.
; On entry, HL points to start of search area.
; The token is in E, and D holds a statement count, decremented from zero.
;; LOOK-PROG
L1D86: LD A,(HL) ; fetch current character
CP $3A ; is it ':' a statement separator ?
JR Z,L1DA3 ; forward to LOOK-P-2 if so.
; The starting point was PROG - 1 or the end of a line.
;; LOOK-P-1
L1D8B: INC HL ; increment pointer to address
LD A,(HL) ; the high byte of line number
AND $C0 ; test for program end marker $80 or a
; variable
SCF ; Set Carry Flag
RET NZ ; return with carry set if at end
; of program. ->
LD B,(HL) ; high byte of line number to B
INC HL ;
LD C,(HL) ; low byte to C.
LD ($5C42),BC ; set system variable NEWPPC.
INC HL ;
LD C,(HL) ; low byte of line length to C.
INC HL ;
LD B,(HL) ; high byte to B.
PUSH HL ; save address
ADD HL,BC ; add length to position.
LD B,H ; and save result
LD C,L ; in BC.
POP HL ; restore address.
LD D,$00 ; initialize statement counter to zero.
;; LOOK-P-2
L1DA3: PUSH BC ; save address of next line
CALL L198B ; routine EACH-STMT searches current line.
POP BC ; restore address.
RET NC ; return if match was found. ->
JR L1D8B ; back to LOOK-P-1 for next line.
; -------------------
; Handle NEXT command
; -------------------
; e.g. NEXT i
; The parameter tables have already evaluated the presence of a variable
;; NEXT
L1DAB: BIT 1,(IY+$37) ; test FLAGX - handling a new variable ?
JP NZ,L1C2E ; jump back to REPORT-2 if so
; 'Variable not found'
; now test if found variable is a simple variable uninitialized by a FOR.
LD HL,($5C4D) ; load address of variable from DEST
BIT 7,(HL) ; is it correct type ?
JR Z,L1DD8 ; forward to REPORT-1 if not
; 'NEXT without FOR'
INC HL ; step past variable name
LD ($5C68),HL ; and set MEM to point to three 5-byte values
; value, limit, step.
RST 28H ;; FP-CALC add step and re-store
DB $E0 ;;get-mem-0 v.
DB $E2 ;;get-mem-2 v,s.
DB $0F ;;addition v+s.
DB $C0 ;;st-mem-0 v+s.
DB $02 ;;delete .
DB $38 ;;end-calc
CALL L1DDA ; routine NEXT-LOOP tests against limit.
RET C ; return if no more iterations possible.
LD HL,($5C68) ; find start of variable contents from MEM.
LD DE,$000F ; add 3*5 to
ADD HL,DE ; address the looping line number
LD E,(HL) ; low byte to E
INC HL ;
LD D,(HL) ; high byte to D
INC HL ; address looping statement
LD H,(HL) ; and store in H
EX DE,HL ; swap registers
JP L1E73 ; exit via GO-TO-2 to execute another loop.
; ---
;; REPORT-1
L1DD8: RST 08H ; ERROR-1
DB $00 ; Error Report: NEXT without FOR
; -----------------
; Perform NEXT loop
; -----------------
; This routine is called from the FOR command to test for an initial
; iteration and from the NEXT command to test for all subsequent iterations.
; the system variable MEM addresses the variable's contents which, in the
; latter case, have had the step, possibly negative, added to the value.
;; NEXT-LOOP
L1DDA: RST 28H ;; FP-CALC
DB $E1 ;;get-mem-1 l.
DB $E0 ;;get-mem-0 l,v.
DB $E2 ;;get-mem-2 l,v,s.
DB $36 ;;less-0 l,v,(1/0) negative step ?
DB $00 ;;jump-true l,v.(1/0)
DB $02 ;;to L1DE2, NEXT-1 if step negative
DB $01 ;;exchange v,l.
;; NEXT-1
L1DE2: DB $03 ;;subtract l-v OR v-l.
DB $37 ;;greater-0 (1/0)
DB $00 ;;jump-true .
DB $04 ;;to L1DE9, NEXT-2 if no more iterations.
DB $38 ;;end-calc .
AND A ; clear carry flag signalling another loop.
RET ; return
; ---
;; NEXT-2
L1DE9: DB $38 ;;end-calc .
SCF ; set carry flag signalling looping exhausted.
RET ; return
; -------------------
; Handle READ command
; -------------------
; e.g. READ a, b$, c$(1000 TO 3000)
; A list of comma-separated variables is assigned from a list of
; comma-separated expressions.
; As it moves along the first list, the character address CH_ADD is stored
; in X_PTR while CH_ADD is used to read the second list.
;; READ-3
L1DEC: RST 20H ; NEXT-CHAR
; -> Entry point.
;; READ
L1DED: CALL L1C1F ; routine CLASS-01 checks variable.
CALL L2530 ; routine SYNTAX-Z
JR Z,L1E1E ; forward to READ-2 if checking syntax
RST 18H ; GET-CHAR
LD ($5C5F),HL ; save character position in X_PTR.
LD HL,($5C57) ; load HL with Data Address DATADD, which is
; the start of the program or the address
; after the last expression that was read or
; the address of the line number of the
; last RESTORE command.
LD A,(HL) ; fetch character
CP $2C ; is it a comma ?
JR Z,L1E0A ; forward to READ-1 if so.
; else all data in this statement has been read so look for next DATA token
LD E,$E4 ; token 'DATA'
CALL L1D86 ; routine LOOK-PROG
JR NC,L1E0A ; forward to READ-1 if DATA found
; else report the error.
;; REPORT-E
L1E08: RST 08H ; ERROR-1
DB $0D ; Error Report: Out of DATA
;; READ-1
L1E0A: CALL L0077 ; routine TEMP-PTR1 advances updating CH_ADD
; with new DATADD position.
CALL L1C56 ; routine VAL-FET-1 assigns value to variable
; checking type match and adjusting CH_ADD.
RST 18H ; GET-CHAR fetches adjusted character position
LD ($5C57),HL ; store back in DATADD
LD HL,($5C5F) ; fetch X_PTR the original READ CH_ADD
LD (IY+$26),$00 ; now nullify X_PTR_hi
CALL L0078 ; routine TEMP-PTR2 restores READ CH_ADD
;; READ-2
L1E1E: RST 18H ; GET-CHAR
CP $2C ; is it ',' indicating more variables to read ?
JR Z,L1DEC ; back to READ-3 if so
CALL L1BEE ; routine CHECK-END
RET ; return from here in runtime to STMT-RET.
; -------------------
; Handle DATA command
; -------------------
; In runtime this 'command' is passed by but the syntax is checked when such
; a statement is found while parsing a line.
; e.g. DATA 1, 2, "text", score-1, a$(location, room, object), FN r(49),
; wages - tax, TRUE, The meaning of life
;; DATA
L1E27: CALL L2530 ; routine SYNTAX-Z to check status
JR NZ,L1E37 ; forward to DATA-2 if in runtime
;; DATA-1
L1E2C: CALL L24FB ; routine SCANNING to check syntax of
; expression
CP $2C ; is it a comma ?
CALL NZ,L1BEE ; routine CHECK-END checks that statement
; is complete. Will make an early exit if
; so. >>>
RST 20H ; NEXT-CHAR
JR L1E2C ; back to DATA-1
; ---
;; DATA-2
L1E37: LD A,$E4 ; set token to 'DATA' and continue into
; the the PASS-BY routine.
; ----------------------------------
; Check statement for DATA or DEF FN
; ----------------------------------
; This routine is used to backtrack to a command token and then
; forward to the next statement in runtime.
;; PASS-BY
L1E39: LD B,A ; Give BC enough space to find token.
CPDR ; Compare decrement and repeat. (Only use).
; Work backwards till keyword is found which
; is start of statement before any quotes.
; HL points to location before keyword.
LD DE,$0200 ; count 1+1 statements, dummy value in E to
; inhibit searching for a token.
JP L198B ; to EACH-STMT to find next statement
; -----------------------------------------------------------------------
; A General Note on Invalid Line Numbers.
; =======================================
; One of the revolutionary concepts of Sinclair BASIC was that it supported
; virtual line numbers. That is the destination of a GO TO, RESTORE etc. need
; not exist. It could be a point before or after an actual line number.
; Zero suffices for a before but the after should logically be infinity.
; Since the maximum actual line limit is 9999 then the system limit, 16383
; when variables kick in, would serve fine as a virtual end point.
; However, ironically, only the LOAD command gets it right. It will not
; autostart a program that has been saved with a line higher than 16383.
; All the other commands deal with the limit unsatisfactorily.
; LIST, RUN, GO TO, GO SUB and RESTORE have problems and the latter may
; crash the machine when supplied with an inappropriate virtual line number.
; This is puzzling as very careful consideration must have been given to
; this point when the new variable types were allocated their masks and also
; when the routine NEXT-ONE was successfully re-written to reflect this.
; An enigma.
; -------------------------------------------------------------------------
; ----------------------
; Handle RESTORE command
; ----------------------
; The restore command sets the system variable for the data address to
; point to the location before the supplied line number or first line
; thereafter.
; This alters the position where subsequent READ commands look for data.
; Note. If supplied with inappropriate high numbers the system may crash
; in the LINE-ADDR routine as it will pass the program/variables end-marker
; and then lose control of what it is looking for - variable or line number.
; - observation, Steven Vickers, 1984, Pitman.
;; RESTORE
L1E42: CALL L1E99 ; routine FIND-INT2 puts integer in BC.
; Note. B should be checked against limit $3F
; and an error generated if higher.
; this entry point is used from RUN command with BC holding zero
;; REST-RUN
L1E45: LD H,B ; transfer the line
LD L,C ; number to the HL register.
CALL L196E ; routine LINE-ADDR to fetch the address.
DEC HL ; point to the location before the line.
LD ($5C57),HL ; update system variable DATADD.
RET ; return to STMT-RET (or RUN)
; ------------------------
; Handle RANDOMIZE command
; ------------------------
; This command sets the SEED for the RND function to a fixed value.
; With the parameter zero, a random start point is used depending on
; how long the computer has been switched on.
;; RANDOMIZE
L1E4F: CALL L1E99 ; routine FIND-INT2 puts parameter in BC.
LD A,B ; test this
OR C ; for zero.
JR NZ,L1E5A ; forward to RAND-1 if not zero.
LD BC,($5C78) ; use the lower two bytes at FRAMES1.
;; RAND-1
L1E5A: LD ($5C76),BC ; place in SEED system variable.
RET ; return to STMT-RET
; -----------------------
; Handle CONTINUE command
; -----------------------
; The CONTINUE command transfers the OLD (but incremented) values of
; line number and statement to the equivalent "NEW VALUE" system variables
; by using the last part of GO TO and exits indirectly to STMT-RET.
;; CONTINUE
L1E5F: LD HL,($5C6E) ; fetch OLDPPC line number.
LD D,(IY+$36) ; fetch OSPPC statement.
JR L1E73 ; forward to GO-TO-2
; --------------------
; Handle GO TO command
; --------------------
; The GO TO command routine is also called by GO SUB and RUN routines
; to evaluate the parameters of both commands.
; It updates the system variables used to fetch the next line/statement.
; It is at STMT-RET that the actual change in control takes place.
; Unlike some BASICs the line number need not exist.
; Note. the high byte of the line number is incorrectly compared with $F0
; instead of $3F. This leads to commands with operands greater than 32767
; being considered as having been run from the editing area and the
; error report 'Statement Lost' is given instead of 'OK'.
; - Steven Vickers, 1984.
;; GO-TO
L1E67: CALL L1E99 ; routine FIND-INT2 puts operand in BC
LD H,B ; transfer line
LD L,C ; number to HL.
LD D,$00 ; set statement to 0 - first.
LD A,H ; compare high byte only
CP $F0 ; to $F0 i.e. 61439 in full.
JR NC,L1E9F ; forward to REPORT-B if above.
; This call entry point is used to update the system variables e.g. by RETURN.
;; GO-TO-2
L1E73: LD ($5C42),HL ; save line number in NEWPPC
LD (IY+$0A),D ; and statement in NSPPC
RET ; to STMT-RET (or GO-SUB command)
; ------------------
; Handle OUT command
; ------------------
; Syntax has been checked and the two comma-separated values are on the
; calculator stack.
;; OUT
L1E7A: CALL L1E85 ; routine TWO-PARAM fetches values
; to BC and A.
OUT (C),A ; perform the operation.
RET ; return to STMT-RET.
; -------------------
; Handle POKE command
; -------------------
; This routine alters a single byte in the 64K address space.
; Happily no check is made as to whether ROM or RAM is addressed.
; Sinclair BASIC requires no poking of system variables.
;; POKE
L1E80: CALL L1E85 ; routine TWO-PARAM fetches values
; to BC and A.
LD (BC),A ; load memory location with A.
RET ; return to STMT-RET.
; ------------------------------------
; Fetch two parameters from calculator stack
; ------------------------------------
; This routine fetches a byte and word from the calculator stack
; producing an error if either is out of range.
;; TWO-PARAM
L1E85: CALL L2DD5 ; routine FP-TO-A
JR C,L1E9F ; forward to REPORT-B if overflow occurred
JR Z,L1E8E ; forward to TWO-P-1 if positive
NEG ; negative numbers are made positive
;; TWO-P-1
L1E8E: PUSH AF ; save the value
CALL L1E99 ; routine FIND-INT2 gets integer to BC
POP AF ; restore the value
RET ; return
; -------------
; Find integers
; -------------
; The first of these routines fetches a 8-bit integer (range 0-255) from the
; calculator stack to the accumulator and is used for colours, streams,
; durations and coordinates.
; The second routine fetches 16-bit integers to the BC register pair
; and is used to fetch command and function arguments involving line numbers
; or memory addresses and also array subscripts and tab arguments.
; ->
;; FIND-INT1
L1E94: CALL L2DD5 ; routine FP-TO-A
JR L1E9C ; forward to FIND-I-1 for common exit routine.
; ---
; ->
;; FIND-INT2
L1E99: CALL L2DA2 ; routine FP-TO-BC
;; FIND-I-1
L1E9C: JR C,L1E9F ; to REPORT-Bb with overflow.
RET Z ; return if positive.
;; REPORT-Bb
L1E9F: RST 08H ; ERROR-1
DB $0A ; Error Report: Integer out of range
; ------------------
; Handle RUN command
; ------------------
; This command runs a program starting at an optional line.
; It performs a 'RESTORE 0' then CLEAR
;; RUN
L1EA1: CALL L1E67 ; routine GO-TO puts line number in
; system variables.
LD BC,$0000 ; prepare to set DATADD to first line.
CALL L1E45 ; routine REST-RUN does the 'restore'.
; Note BC still holds zero.
JR L1EAF ; forward to CLEAR-RUN to clear variables
; without disturbing RAMTOP and
; exit indirectly to STMT-RET
; --------------------
; Handle CLEAR command
; --------------------
; This command reclaims the space used by the variables.
; It also clears the screen and the GO SUB stack.
; With an integer expression, it sets the uppermost memory
; address within the BASIC system.
; "Contrary to the manual, CLEAR doesn't execute a RESTORE" -
; Steven Vickers, Pitman Pocket Guide to the Spectrum, 1984.
;; CLEAR
L1EAC: CALL L1E99 ; routine FIND-INT2 fetches to BC.
;; CLEAR-RUN
L1EAF: LD A,B ; test for
OR C ; zero.
JR NZ,L1EB7 ; skip to CLEAR-1 if not zero.
LD BC,($5CB2) ; use the existing value of RAMTOP if zero.
;; CLEAR-1
L1EB7: PUSH BC ; save ramtop value.
LD DE,($5C4B) ; fetch VARS
LD HL,($5C59) ; fetch E_LINE
DEC HL ; adjust to point at variables end-marker.
CALL L19E5 ; routine RECLAIM-1 reclaims the space used by
; the variables.
CALL L0D6B ; routine CLS to clear screen.
LD HL,($5C65) ; fetch STKEND the start of free memory.
LD DE,$0032 ; allow for another 50 bytes.
ADD HL,DE ; add the overhead to HL.
POP DE ; restore the ramtop value.
SBC HL,DE ; if HL is greater than the value then jump
JR NC,L1EDA ; forward to REPORT-M
; 'RAMTOP no good'
LD HL,($5CB4) ; now P-RAMT ($7FFF on 16K RAM machine)
AND A ; exact this time.
SBC HL,DE ; new ramtop must be lower or the same.
JR NC,L1EDC ; skip to CLEAR-2 if in actual RAM.
;; REPORT-M
L1EDA: RST 08H ; ERROR-1
DB $15 ; Error Report: RAMTOP no good
;; CLEAR-2
L1EDC: EX DE,HL ; transfer ramtop value to HL.
LD ($5CB2),HL ; update system variable RAMTOP.
POP DE ; pop the return address STMT-RET.
POP BC ; pop the Error Address.
LD (HL),$3E ; now put the GO SUB end-marker at RAMTOP.
DEC HL ; leave a location beneath it.
LD SP,HL ; initialize the machine stack pointer.
PUSH BC ; push the error address.
LD ($5C3D),SP ; make ERR_SP point to location.
EX DE,HL ; put STMT-RET in HL.
JP (HL) ; and go there directly.
; ---------------------
; Handle GO SUB command
; ---------------------
; The GO SUB command diverts BASIC control to a new line number
; in a very similar manner to GO TO but
; the current line number and current statement + 1
; are placed on the GO SUB stack as a RETURN point.
;; GO-SUB
L1EED: POP DE ; drop the address STMT-RET
LD H,(IY+$0D) ; fetch statement from SUBPPC and
INC H ; increment it
EX (SP),HL ; swap - error address to HL,
; H (statement) at top of stack,
; L (unimportant) beneath.
INC SP ; adjust to overwrite unimportant byte
LD BC,($5C45) ; fetch the current line number from PPC
PUSH BC ; and PUSH onto GO SUB stack.
; the empty machine-stack can be rebuilt
PUSH HL ; push the error address.
LD ($5C3D),SP ; make system variable ERR_SP point to it.
PUSH DE ; push the address STMT-RET.
CALL L1E67 ; call routine GO-TO to update the system
; variables NEWPPC and NSPPC.
; then make an indirect exit to STMT-RET via
LD BC,$0014 ; a 20-byte overhead memory check.
; ----------------------
; Check available memory
; ----------------------
; This routine is used on many occasions when extending a dynamic area
; upwards or the GO SUB stack downwards.
;; TEST-ROOM
L1F05: LD HL,($5C65) ; fetch STKEND
ADD HL,BC ; add the supplied test value
JR C,L1F15 ; forward to REPORT-4 if over $FFFF
EX DE,HL ; was less so transfer to DE
LD HL,$0050 ; test against another 80 bytes
ADD HL,DE ; anyway
JR C,L1F15 ; forward to REPORT-4 if this passes $FFFF
SBC HL,SP ; if less than the machine stack pointer
RET C ; then return - OK.
;; REPORT-4
L1F15: LD L,$03 ; prepare 'Out of Memory'
JP L0055 ; jump back to ERROR-3 at $0055
; Note. this error can't be trapped at $0008
; ------------------------------
; THE 'FREE MEMORY' USER ROUTINE
; ------------------------------
; This routine is not used by the ROM but allows users to evaluate
; approximate free memory with PRINT 65536 - USR 7962.
;; free-mem
L1F1A: LD BC,$0000 ; allow no overhead.
CALL L1F05 ; routine TEST-ROOM.
LD B,H ; transfer the result
LD C,L ; to the BC register.
RET ; the USR function returns value of BC.
; --------------------
; THE 'RETURN' COMMAND
; --------------------
; As with any command, there are two values on the machine stack at the time
; it is invoked. The machine stack is below the GOSUB stack. Both grow
; downwards, the machine stack by two bytes, the GOSUB stack by 3 bytes.
; The highest location is a statement byte followed by a two-byte line number.
;; RETURN
L1F23: POP BC ; drop the address STMT-RET.
POP HL ; now the error address.
POP DE ; now a possible BASIC return line.
LD A,D ; the high byte $00 - $27 is
CP $3E ; compared with the traditional end-marker $3E.
JR Z,L1F36 ; forward to REPORT-7 with a match.
; 'RETURN without GOSUB'
; It was not the end-marker so a single statement byte remains at the base of
; the calculator stack. It can't be popped off.
DEC SP ; adjust stack pointer to create room for two
; bytes.
EX (SP),HL ; statement to H, error address to base of
; new machine stack.
EX DE,HL ; statement to D, BASIC line number to HL.
LD ($5C3D),SP ; adjust ERR_SP to point to new stack pointer
PUSH BC ; now re-stack the address STMT-RET
JP L1E73 ; to GO-TO-2 to update statement and line
; system variables and exit indirectly to the
; address just pushed on stack.
; ---
;; REPORT-7
L1F36: PUSH DE ; replace the end-marker.
PUSH HL ; now restore the error address
; as will be required in a few clock cycles.
RST 08H ; ERROR-1
DB $06 ; Error Report: RETURN without GOSUB
; --------------------
; Handle PAUSE command
; --------------------
; The pause command takes as its parameter the number of interrupts
; for which to wait. PAUSE 50 pauses for about a second.
; PAUSE 0 pauses indefinitely.
; Both forms can be finished by pressing a key.
;; PAUSE
L1F3A: CALL L1E99 ; routine FIND-INT2 puts value in BC
;; PAUSE-1
L1F3D: HALT ; wait for interrupt.
DEC BC ; decrease counter.
LD A,B ; test if
OR C ; result is zero.
JR Z,L1F4F ; forward to PAUSE-END if so.
LD A,B ; test if
AND C ; now $FFFF
INC A ; that is, initially zero.
JR NZ,L1F49 ; skip forward to PAUSE-2 if not.
INC BC ; restore counter to zero.
;; PAUSE-2
L1F49: BIT 5,(IY+$01) ; test FLAGS - has a new key been pressed ?
JR Z,L1F3D ; back to PAUSE-1 if not.
;; PAUSE-END
L1F4F: RES 5,(IY+$01) ; update FLAGS - signal no new key
RET ; and return.
; -------------------
; Check for BREAK key
; -------------------
; This routine is called from COPY-LINE, when interrupts are disabled,
; to test if BREAK (SHIFT - SPACE) is being pressed.
; It is also called at STMT-RET after every statement.
;; BREAK-KEY
L1F54: LD A,$7F ; Input address: $7FFE
IN A,($FE) ; read lower right keys
RRA ; rotate bit 0 - SPACE
RET C ; return if not reset
LD A,$FE ; Input address: $FEFE
IN A,($FE) ; read lower left keys
RRA ; rotate bit 0 - SHIFT
RET ; carry will be set if not pressed.
; return with no carry if both keys
; pressed.
; ---------------------
; Handle DEF FN command
; ---------------------
; e.g DEF FN r$(a$,a) = a$(a TO )
; this 'command' is ignored in runtime but has its syntax checked
; during line-entry.
;; DEF-FN
L1F60: CALL L2530 ; routine SYNTAX-Z
JR Z,L1F6A ; forward to DEF-FN-1 if parsing
LD A,$CE ; else load A with 'DEF FN' and
JP L1E39 ; jump back to PASS-BY
; ---
; continue here if checking syntax.
;; DEF-FN-1
L1F6A: SET 6,(IY+$01) ; set FLAGS - Assume numeric result
CALL L2C8D ; call routine ALPHA
JR NC,L1F89 ; if not then to DEF-FN-4 to jump to
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR
CP $24 ; is it '$' ?
JR NZ,L1F7D ; to DEF-FN-2 if not as numeric.
RES 6,(IY+$01) ; set FLAGS - Signal string result
RST 20H ; get NEXT-CHAR
;; DEF-FN-2
L1F7D: CP $28 ; is it '(' ?
JR NZ,L1FBD ; to DEF-FN-7 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR
CP $29 ; is it ')' ?
JR Z,L1FA6 ; to DEF-FN-6 if null argument
;; DEF-FN-3
L1F86: CALL L2C8D ; routine ALPHA checks that it is the expected
; alphabetic character.
;; DEF-FN-4
L1F89: JP NC,L1C8A ; to REPORT-C if not
; 'Nonsense in BASIC'.
EX DE,HL ; save pointer in DE
RST 20H ; NEXT-CHAR re-initializes HL from CH_ADD
; and advances.
CP $24 ; '$' ? is it a string argument.
JR NZ,L1F94 ; forward to DEF-FN-5 if not.
EX DE,HL ; save pointer to '$' in DE
RST 20H ; NEXT-CHAR re-initializes HL and advances
;; DEF-FN-5
L1F94: EX DE,HL ; bring back pointer.
LD BC,$0006 ; the function requires six hidden bytes for
; each parameter passed.
; The first byte will be $0E
; then 5-byte numeric value
; or 5-byte string pointer.
CALL L1655 ; routine MAKE-ROOM creates space in program
; area.
INC HL ; adjust HL (set by LDDR)
INC HL ; to point to first location.
LD (HL),$0E ; insert the 'hidden' marker.
; Note. these invisible storage locations hold nothing meaningful for the
; moment. They will be used every time the corresponding function is
; evaluated in runtime.
; Now consider the following character fetched earlier.
CP $2C ; is it ',' ? (more than one parameter)
JR NZ,L1FA6 ; to DEF-FN-6 if not
RST 20H ; else NEXT-CHAR
JR L1F86 ; and back to DEF-FN-3
; ---
;; DEF-FN-6
L1FA6: CP $29 ; should close with a ')'
JR NZ,L1FBD ; to DEF-FN-7 if not
; 'Nonsense in BASIC'
RST 20H ; get NEXT-CHAR
CP $3D ; is it '=' ?
JR NZ,L1FBD ; to DEF-FN-7 if not 'Nonsense...'
RST 20H ; address NEXT-CHAR
LD A,($5C3B) ; get FLAGS which has been set above
PUSH AF ; and preserve
CALL L24FB ; routine SCANNING checks syntax of expression
; and also sets flags.
POP AF ; restore previous flags
XOR (IY+$01) ; xor with FLAGS - bit 6 should be same
; therefore will be reset.
AND $40 ; isolate bit 6.
;; DEF-FN-7
L1FBD: JP NZ,L1C8A ; jump back to REPORT-C if the expected result
; is not the same type.
; 'Nonsense in BASIC'
CALL L1BEE ; routine CHECK-END will return early if
; at end of statement and move onto next
; else produce error report. >>>
; There will be no return to here.
; -------------------------------
; Returning early from subroutine
; -------------------------------
; All routines are capable of being run in two modes - syntax checking mode
; and runtime mode. This routine is called often to allow a routine to return
; early if checking syntax.
;; UNSTACK-Z
L1FC3: CALL L2530 ; routine SYNTAX-Z sets zero flag if syntax
; is being checked.
POP HL ; drop the return address.
RET Z ; return to previous call in chain if checking
; syntax.
JP (HL) ; jump to return address as BASIC program is
; actually running.
; ---------------------
; Handle LPRINT command
; ---------------------
; A simple form of 'PRINT #3' although it can output to 16 streams.
; Probably for compatibility with other BASICs particularly ZX81 BASIC.
; An extra UDG might have been better.
;; LPRINT
L1FC9: LD A,$03 ; the printer channel
JR L1FCF ; forward to PRINT-1
; ---------------------
; Handle PRINT commands
; ---------------------
; The Spectrum's main stream output command.
; The default stream is stream 2 which is normally the upper screen
; of the computer. However the stream can be altered in range 0 - 15.
;; PRINT
L1FCD: LD A,$02 ; the stream for the upper screen.
; The LPRINT command joins here.
;; PRINT-1
L1FCF: CALL L2530 ; routine SYNTAX-Z checks if program running
CALL NZ,L1601 ; routine CHAN-OPEN if so
CALL L0D4D ; routine TEMPS sets temporary colours.
CALL L1FDF ; routine PRINT-2 - the actual item
CALL L1BEE ; routine CHECK-END gives error if not at end
; of statement
RET ; and return >>>
; ------------------------------------
; this subroutine is called from above
; and also from INPUT.
;; PRINT-2
L1FDF: RST 18H ; GET-CHAR gets printable character
CALL L2045 ; routine PR-END-Z checks if more printing
JR Z,L1FF2 ; to PRINT-4 if not e.g. just 'PRINT :'
; This tight loop deals with combinations of positional controls and
; print items. An early return can be made from within the loop
; if the end of a print sequence is reached.
;; PRINT-3
L1FE5: CALL L204E ; routine PR-POSN-1 returns zero if more
; but returns early at this point if
; at end of statement!
;
JR Z,L1FE5 ; to PRINT-3 if consecutive positioners
CALL L1FFC ; routine PR-ITEM-1 deals with strings etc.
CALL L204E ; routine PR-POSN-1 for more position codes
JR Z,L1FE5 ; loop back to PRINT-3 if so
;; PRINT-4
L1FF2: CP $29 ; return now if this is ')' from input-item.
; (see INPUT.)
RET Z ; or continue and print carriage return in
; runtime
; ---------------------
; Print carriage return
; ---------------------
; This routine which continues from above prints a carriage return
; in run-time. It is also called once from PRINT-POSN.
;; PRINT-CR
L1FF5: CALL L1FC3 ; routine UNSTACK-Z
LD A,$0D ; prepare a carriage return
RST 10H ; PRINT-A
RET ; return
; -----------
; Print items
; -----------
; This routine deals with print items as in
; PRINT AT 10,0;"The value of A is ";a
; It returns once a single item has been dealt with as it is part
; of a tight loop that considers sequences of positional and print items
;; PR-ITEM-1
L1FFC: RST 18H ; GET-CHAR
CP $AC ; is character 'AT' ?
JR NZ,L200E ; forward to PR-ITEM-2 if not.
CALL L1C79 ; routine NEXT-2NUM check for two comma
; separated numbers placing them on the
; calculator stack in runtime.
CALL L1FC3 ; routine UNSTACK-Z quits if checking syntax.
CALL L2307 ; routine STK-TO-BC get the numbers in B and C.
LD A,$16 ; prepare the 'at' control.
JR L201E ; forward to PR-AT-TAB to print the sequence.
; ---
;; PR-ITEM-2
L200E: CP $AD ; is character 'TAB' ?
JR NZ,L2024 ; to PR-ITEM-3 if not
RST 20H ; NEXT-CHAR to address next character
CALL L1C82 ; routine EXPT-1NUM
CALL L1FC3 ; routine UNSTACK-Z quits if checking syntax.
CALL L1E99 ; routine FIND-INT2 puts integer in BC.
LD A,$17 ; prepare the 'tab' control.
;; PR-AT-TAB
L201E: RST 10H ; PRINT-A outputs the control
LD A,C ; first value to A
RST 10H ; PRINT-A outputs it.
LD A,B ; second value
RST 10H ; PRINT-A
RET ; return - item finished >>>
; ---
; Now consider paper 2; #2; a$
;; PR-ITEM-3
L2024: CALL L21F2 ; routine CO-TEMP-3 will print any colour
RET NC ; items - return if success.
CALL L2070 ; routine STR-ALTER considers new stream
RET NC ; return if altered.
CALL L24FB ; routine SCANNING now to evaluate expression
CALL L1FC3 ; routine UNSTACK-Z if not runtime.
BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ?
CALL Z,L2BF1 ; routine STK-FETCH if string.
; note no flags affected.
JP NZ,L2DE3 ; to PRINT-FP to print if numeric >>>
; It was a string expression - start in DE, length in BC
; Now enter a loop to print it
;; PR-STRING
L203C: LD A,B ; this tests if the
OR C ; length is zero and sets flag accordingly.
DEC BC ; this doesn't but decrements counter.
RET Z ; return if zero.
LD A,(DE) ; fetch character.
INC DE ; address next location.
RST 10H ; PRINT-A.
JR L203C ; loop back to PR-STRING.
; ---------------
; End of printing
; ---------------
; This subroutine returns zero if no further printing is required
; in the current statement.
; The first terminator is found in escaped input items only,
; the others in print_items.
;; PR-END-Z
L2045: CP $29 ; is character a ')' ?
RET Z ; return if so - e.g. INPUT (p$); a$
;; PR-ST-END
L2048: CP $0D ; is it a carriage return ?
RET Z ; return also - e.g. PRINT a
CP $3A ; is character a ':' ?
RET ; return - zero flag will be set if so.
; e.g. PRINT a :
; --------------
; Print position
; --------------
; This routine considers a single positional character ';', ',', '''
;; PR-POSN-1
L204E: RST 18H ; GET-CHAR
CP $3B ; is it ';' ?
; i.e. print from last position.
JR Z,L2067 ; forward to PR-POSN-3 if so.
; i.e. do nothing.
CP $2C ; is it ',' ?
; i.e. print at next tabstop.
JR NZ,L2061 ; forward to PR-POSN-2 if anything else.
CALL L2530 ; routine SYNTAX-Z
JR Z,L2067 ; forward to PR-POSN-3 if checking syntax.
LD A,$06 ; prepare the 'comma' control character.
RST 10H ; PRINT-A outputs to current channel in
; run-time.
JR L2067 ; skip to PR-POSN-3.
; ---
; check for newline.
;; PR-POSN-2
L2061: CP $27 ; is character a "'" ? (newline)
RET NZ ; return if no match >>>
CALL L1FF5 ; routine PRINT-CR outputs a carriage return
; in runtime only.
;; PR-POSN-3
L2067: RST 20H ; NEXT-CHAR to A.
CALL L2045 ; routine PR-END-Z checks if at end.
JR NZ,L206E ; to PR-POSN-4 if not.
POP BC ; drop return address if at end.
;; PR-POSN-4
L206E: CP A ; reset the zero flag.
RET ; and return to loop or quit.
; ------------
; Alter stream
; ------------
; This routine is called from PRINT ITEMS above, and also LIST as in
; LIST #15
;; STR-ALTER
L2070: CP $23 ; is character '#' ?
SCF ; set carry flag.
RET NZ ; return if no match.
RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM gets stream number
AND A ; prepare to exit early with carry reset
CALL L1FC3 ; routine UNSTACK-Z exits early if parsing
CALL L1E94 ; routine FIND-INT1 gets number off stack
CP $10 ; must be range 0 - 15 decimal.
JP NC,L160E ; jump back to REPORT-Oa if not
; 'Invalid stream'.
CALL L1601 ; routine CHAN-OPEN
AND A ; clear carry - signal item dealt with.
RET ; return
; --------------------
; Handle INPUT command
; --------------------
; This command
;
;; INPUT
L2089: CALL L2530 ; routine SYNTAX-Z to check if in runtime.
JR Z,L2096 ; forward to INPUT-1 if checking syntax.
LD A,$01 ; select channel 'K' the keyboard for input.
CALL L1601 ; routine CHAN-OPEN opens it.
CALL L0D6E ; routine CLS-LOWER clears the lower screen
; and sets DF_SZ to two.
;; INPUT-1
L2096: LD (IY+$02),$01 ; update TV_FLAG - signal lower screen in use
; ensuring that the correct set of system
; variables are updated and that the border
; colour is used.
CALL L20C1 ; routine IN-ITEM-1 to handle the input.
CALL L1BEE ; routine CHECK-END will make an early exit
; if checking syntax. >>>
; keyboard input has been made and it remains to adjust the upper
; screen in case the lower two lines have been extended upwards.
LD BC,($5C88) ; fetch S_POSN current line/column of
; the upper screen.
LD A,($5C6B) ; fetch DF_SZ the display file size of
; the lower screen.
CP B ; test that lower screen does not overlap
JR C,L20AD ; forward to INPUT-2 if not.
; the two screens overlap so adjust upper screen.
LD C,$21 ; set column of upper screen to leftmost.
LD B,A ; and line to one above lower screen.
; continue forward to update upper screen
; print position.
;; INPUT-2
L20AD: LD ($5C88),BC ; set S_POSN update upper screen line/column.
LD A,$19 ; subtract from twenty five
SUB B ; the new line number.
LD ($5C8C),A ; and place result in SCR_CT - scroll count.
RES 0,(IY+$02) ; update TV_FLAG - signal main screen in use.
CALL L0DD9 ; routine CL-SET sets the print position
; system variables for the upper screen.
JP L0D6E ; jump back to CLS-LOWER and make
; an indirect exit >>.
; ---------------------
; INPUT ITEM subroutine
; ---------------------
; This subroutine deals with the input items and print items.
; from the current input channel.
; It is only called from the above INPUT routine but was obviously
; once called from somewhere else in another context.
;; IN-ITEM-1
L20C1: CALL L204E ; routine PR-POSN-1 deals with a single
; position item at each call.
JR Z,L20C1 ; back to IN-ITEM-1 until no more in a
; sequence.
CP $28 ; is character '(' ?
JR NZ,L20D8 ; forward to IN-ITEM-2 if not.
; any variables within braces will be treated as part, or all, of the prompt
; instead of being used as destination variables.
RST 20H ; NEXT-CHAR
CALL L1FDF ; routine PRINT-2 to output the dynamic
; prompt.
RST 18H ; GET-CHAR
CP $29 ; is character a matching ')' ?
JP NZ,L1C8A ; jump back to REPORT-C if not.
; 'Nonsense in BASIC'.
RST 20H ; NEXT-CHAR
JP L21B2 ; forward to IN-NEXT-2
; ---
;; IN-ITEM-2
L20D8: CP $CA ; is the character the token 'LINE' ?
JR NZ,L20ED ; forward to IN-ITEM-3 if not.
RST 20H ; NEXT-CHAR - variable must come next.
CALL L1C1F ; routine CLASS-01 returns destination
; address of variable to be assigned.
; or generates an error if no variable
; at this position.
SET 7,(IY+$37) ; update FLAGX - signal handling INPUT LINE
BIT 6,(IY+$01) ; test FLAGS - numeric or string result ?
JP NZ,L1C8A ; jump back to REPORT-C if not string
; 'Nonsense in BASIC'.
JR L20FA ; forward to IN-PROMPT to set up workspace.
; ---
; the jump was here for other variables.
;; IN-ITEM-3
L20ED: CALL L2C8D ; routine ALPHA checks if character is
; a suitable variable name.
JP NC,L21AF ; forward to IN-NEXT-1 if not
CALL L1C1F ; routine CLASS-01 returns destination
; address of variable to be assigned.
RES 7,(IY+$37) ; update FLAGX - signal not INPUT LINE.
;; IN-PROMPT
L20FA: CALL L2530 ; routine SYNTAX-Z
JP Z,L21B2 ; forward to IN-NEXT-2 if checking syntax.
CALL L16BF ; routine SET-WORK clears workspace.
LD HL,$5C71 ; point to system variable FLAGX
RES 6,(HL) ; signal string result.
SET 5,(HL) ; signal in Input Mode for editor.
LD BC,$0001 ; initialize space required to one for
; the carriage return.
BIT 7,(HL) ; test FLAGX - INPUT LINE in use ?
JR NZ,L211C ; forward to IN-PR-2 if so as that is
; all the space that is required.
LD A,($5C3B) ; load accumulator from FLAGS
AND $40 ; mask to test BIT 6 of FLAGS and clear
; the other bits in A.
; numeric result expected ?
JR NZ,L211A ; forward to IN-PR-1 if so
LD C,$03 ; increase space to three bytes for the
; pair of surrounding quotes.
;; IN-PR-1
L211A: OR (HL) ; if numeric result, set bit 6 of FLAGX.
LD (HL),A ; and update system variable
;; IN-PR-2
L211C: RST 30H ; BC-SPACES opens 1 or 3 bytes in workspace
LD (HL),$0D ; insert carriage return at last new location.
LD A,C ; fetch the length, one or three.
RRCA ; lose bit 0.
RRCA ; test if quotes required.
JR NC,L2129 ; forward to IN-PR-3 if not.
LD A,$22 ; load the '"' character
LD (DE),A ; place quote in first new location at DE.
DEC HL ; decrease HL - from carriage return.
LD (HL),A ; and place a quote in second location.
;; IN-PR-3
L2129: LD ($5C5B),HL ; set keyboard cursor K_CUR to HL
BIT 7,(IY+$37) ; test FLAGX - is this INPUT LINE ??
JR NZ,L215E ; forward to IN-VAR-3 if so as input will
; be accepted without checking its syntax.
LD HL,($5C5D) ; fetch CH_ADD
PUSH HL ; and save on stack.
LD HL,($5C3D) ; fetch ERR_SP
PUSH HL ; and save on stack
;; IN-VAR-1
L213A: LD HL,L213A ; address: IN-VAR-1 - this address
PUSH HL ; is saved on stack to handle errors.
BIT 4,(IY+$30) ; test FLAGS2 - is K channel in use ?
JR Z,L2148 ; forward to IN-VAR-2 if not using the
; keyboard for input. (??)
LD ($5C3D),SP ; set ERR_SP to point to IN-VAR-1 on stack.
;; IN-VAR-2
L2148: LD HL,($5C61) ; set HL to WORKSP - start of workspace.
CALL L11A7 ; routine REMOVE-FP removes floating point
; forms when looping in error condition.
LD (IY+$00),$FF ; set ERR_NR to 'OK' cancelling the error.
; but X_PTR causes flashing error marker
; to be displayed at each call to the editor.
CALL L0F2C ; routine EDITOR allows input to be entered
; or corrected if this is second time around.
; if we pass to next then there are no system errors
RES 7,(IY+$01) ; update FLAGS - signal checking syntax
CALL L21B9 ; routine IN-ASSIGN checks syntax using
; the VAL-FET-2 and powerful SCANNING routines.
; any syntax error and its back to IN-VAR-1.
; but with the flashing error marker showing
; where the error is.
; Note. the syntax of string input has to be
; checked as the user may have removed the
; bounding quotes or escaped them as with
; "hat" + "stand" for example.
; proceed if syntax passed.
JR L2161 ; jump forward to IN-VAR-4
; ---
; the jump was to here when using INPUT LINE.
;; IN-VAR-3
L215E: CALL L0F2C ; routine EDITOR is called for input
; when ENTER received rejoin other route but with no syntax check.
; INPUT and INPUT LINE converge here.
;; IN-VAR-4
L2161: LD (IY+$22),$00 ; set K_CUR_hi to a low value so that the cursor
; no longer appears in the input line.
CALL L21D6 ; routine IN-CHAN-K tests if the keyboard
; is being used for input.
JR NZ,L2174 ; forward to IN-VAR-5 if using another input
; channel.
; continue here if using the keyboard.
CALL L111D ; routine ED-COPY overprints the edit line
; to the lower screen. The only visible
; affect is that the cursor disappears.
; if you're inputting more than one item in
; a statement then that becomes apparent.
LD BC,($5C82) ; fetch line and column from ECHO_E
CALL L0DD9 ; routine CL-SET sets S-POSNL to those
; values.
; if using another input channel rejoin here.
;; IN-VAR-5
L2174: LD HL,$5C71 ; point HL to FLAGX
RES 5,(HL) ; signal not in input mode
BIT 7,(HL) ; is this INPUT LINE ?
RES 7,(HL) ; cancel the bit anyway.
JR NZ,L219B ; forward to IN-VAR-6 if INPUT LINE.
POP HL ; drop the looping address
POP HL ; drop the the address of previous
; error handler.
LD ($5C3D),HL ; set ERR_SP to point to it.
POP HL ; drop original CH_ADD which points to
; INPUT command in BASIC line.
LD ($5C5F),HL ; save in X_PTR while input is assigned.
SET 7,(IY+$01) ; update FLAGS - Signal running program
CALL L21B9 ; routine IN-ASSIGN is called again
; this time the variable will be assigned
; the input value without error.
; Note. the previous example now
; becomes "hatstand"
LD HL,($5C5F) ; fetch stored CH_ADD value from X_PTR.
LD (IY+$26),$00 ; set X_PTR_hi so that iy is no longer relevant.
LD ($5C5D),HL ; put restored value back in CH_ADD
JR L21B2 ; forward to IN-NEXT-2 to see if anything
; more in the INPUT list.
; ---
; the jump was to here with INPUT LINE only
;; IN-VAR-6
L219B: LD HL,($5C63) ; STKBOT points to the end of the input.
LD DE,($5C61) ; WORKSP points to the beginning.
SCF ; prepare for true subtraction.
SBC HL,DE ; subtract to get length
LD B,H ; transfer it to
LD C,L ; the BC register pair.
CALL L2AB2 ; routine STK-STO-$ stores parameters on
; the calculator stack.
CALL L2AFF ; routine LET assigns it to destination.
JR L21B2 ; forward to IN-NEXT-2 as print items
; not allowed with INPUT LINE.
; Note. that "hat" + "stand" will, for
; example, be unchanged as also would
; 'PRINT "Iris was here"'.
; ---
; the jump was to here when ALPHA found more items while looking for
; a variable name.
;; IN-NEXT-1
L21AF: CALL L1FFC ; routine PR-ITEM-1 considers further items.
;; IN-NEXT-2
L21B2: CALL L204E ; routine PR-POSN-1 handles a position item.
JP Z,L20C1 ; jump back to IN-ITEM-1 if the zero flag
; indicates more items are present.
RET ; return.
; ---------------------------
; INPUT ASSIGNMENT Subroutine
; ---------------------------
; This subroutine is called twice from the INPUT command when normal
; keyboard input is assigned. On the first occasion syntax is checked
; using SCANNING. The final call with the syntax flag reset is to make
; the assignment.
;; IN-ASSIGN
L21B9: LD HL,($5C61) ; fetch WORKSP start of input
LD ($5C5D),HL ; set CH_ADD to first character
RST 18H ; GET-CHAR ignoring leading white-space.
CP $E2 ; is it 'STOP'
JR Z,L21D0 ; forward to IN-STOP if so.
LD A,($5C71) ; load accumulator from FLAGX
CALL L1C59 ; routine VAL-FET-2 makes assignment
; or goes through the motions if checking
; syntax. SCANNING is used.
RST 18H ; GET-CHAR
CP $0D ; is it carriage return ?
RET Z ; return if so
; either syntax is OK
; or assignment has been made.
; if another character was found then raise an error.
; User doesn't see report but the flashing error marker
; appears in the lower screen.
;; REPORT-Cb
L21CE: RST 08H ; ERROR-1
DB $0B ; Error Report: Nonsense in BASIC
;; IN-STOP
L21D0: CALL L2530 ; routine SYNTAX-Z (UNSTACK-Z?)
RET Z ; return if checking syntax
; as user wouldn't see error report.
; but generate visible error report
; on second invocation.
;; REPORT-H
L21D4: RST 08H ; ERROR-1
DB $10 ; Error Report: STOP in INPUT
; ------------------
; Test for channel K
; ------------------
; This subroutine is called once from the keyboard
; INPUT command to check if the input routine in
; use is the one for the keyboard.
;; IN-CHAN-K
L21D6: LD HL,($5C51) ; fetch address of current channel CURCHL
INC HL ;
INC HL ; advance past
INC HL ; input and
INC HL ; output streams
LD A,(HL) ; fetch the channel identifier.
CP $4B ; test for 'K'
RET ; return with zero set if keyboard is use.
; --------------------
; Colour Item Routines
; --------------------
;
; These routines have 3 entry points -
; 1) CO-TEMP-2 to handle a series of embedded Graphic colour items.
; 2) CO-TEMP-3 to handle a single embedded print colour item.
; 3) CO TEMP-4 to handle a colour command such as FLASH 1
;
; "Due to a bug, if you bring in a peripheral channel and later use a colour
; statement, colour controls will be sent to it by mistake." - Steven Vickers
; Pitman Pocket Guide, 1984.
;
; To be fair, this only applies if the last channel was other than 'K', 'S'
; or 'P', which are all that are supported by this ROM, but if that last
; channel was a microdrive file, network channel etc. then
; PAPER 6; CLS will not turn the screen yellow and
; CIRCLE INK 2; 128,88,50 will not draw a red circle.
;
; This bug does not apply to embedded PRINT items as it is quite permissible
; to mix stream altering commands and colour items.
; The fix therefore would be to ensure that CLASS-07 and CLASS-09 make
; channel 'S' the current channel when not checking syntax.
; -----------------------------------------------------------------
;; CO-TEMP-1
L21E1: RST 20H ; NEXT-CHAR
; -> Entry point from CLASS-09. Embedded Graphic colour items.
; e.g. PLOT INK 2; PAPER 8; 128,88
; Loops till all colour items output, finally addressing the coordinates.
;; CO-TEMP-2
L21E2: CALL L21F2 ; routine CO-TEMP-3 to output colour control.
RET C ; return if nothing more to output. ->
RST 18H ; GET-CHAR
CP $2C ; is it ',' separator ?
JR Z,L21E1 ; back if so to CO-TEMP-1
CP $3B ; is it ';' separator ?
JR Z,L21E1 ; back to CO-TEMP-1 for more.
JP L1C8A ; to REPORT-C (REPORT-Cb is within range)
; 'Nonsense in BASIC'
; -------------------
; CO-TEMP-3
; -------------------
; -> this routine evaluates and outputs a colour control and parameter.
; It is called from above and also from PR-ITEM-3 to handle a single embedded
; print item e.g. PRINT PAPER 6; "Hi". In the latter case, the looping for
; multiple items is within the PR-ITEM routine.
; It is quite permissible to send these to any stream.
;; CO-TEMP-3
L21F2: CP $D9 ; is it 'INK' ?
RET C ; return if less.
CP $DF ; compare with 'OUT'
CCF ; Complement Carry Flag
RET C ; return if greater than 'OVER', $DE.
PUSH AF ; save the colour token.
RST 20H ; address NEXT-CHAR
POP AF ; restore token and continue.
; -> this entry point used by CLASS-07. e.g. the command PAPER 6.
;; CO-TEMP-4
L21FC: SUB $C9 ; reduce to control character $10 (INK)
; thru $15 (OVER).
PUSH AF ; save control.
CALL L1C82 ; routine EXPT-1NUM stacks addressed
; parameter on calculator stack.
POP AF ; restore control.
AND A ; clear carry
CALL L1FC3 ; routine UNSTACK-Z returns if checking syntax.
PUSH AF ; save again
CALL L1E94 ; routine FIND-INT1 fetches parameter to A.
LD D,A ; transfer now to D
POP AF ; restore control.
RST 10H ; PRINT-A outputs the control to current
; channel.
LD A,D ; transfer parameter to A.
RST 10H ; PRINT-A outputs parameter.
RET ; return. ->
; -------------------------------------------------------------------------
;
; {fl}{br}{ paper }{ ink } The temporary colour attributes
; ___ ___ ___ ___ ___ ___ ___ ___ system variable.
; ATTR_T | | | | | | | | |
; | | | | | | | | |
; 23695 |___|___|___|___|___|___|___|___|
; 7 6 5 4 3 2 1 0
;
;
; {fl}{br}{ paper }{ ink } The temporary mask used for
; ___ ___ ___ ___ ___ ___ ___ ___ transparent colours. Any bit
; MASK_T | | | | | | | | | that is 1 shows that the
; | | | | | | | | | corresponding attribute is
; 23696 |___|___|___|___|___|___|___|___| taken not from ATTR-T but from
; 7 6 5 4 3 2 1 0 what is already on the screen.
;
;
; {paper9 }{ ink9 }{ inv1 }{ over1} The print flags. Even bits are
; ___ ___ ___ ___ ___ ___ ___ ___ temporary flags. The odd bits
; P_FLAG | | | | | | | | | are the permanent flags.
; | p | t | p | t | p | t | p | t |
; 23697 |___|___|___|___|___|___|___|___|
; 7 6 5 4 3 2 1 0
;
; -----------------------------------------------------------------------
; ------------------------------------
; The colour system variable handler.
; ------------------------------------
; This is an exit branch from PO-1-OPER, PO-2-OPER
; A holds control $10 (INK) to $15 (OVER)
; D holds parameter 0-9 for ink/paper 0,1 or 8 for bright/flash,
; 0 or 1 for over/inverse.
;; CO-TEMP-5
L2211: SUB $11 ; reduce range $FF-$04
ADC A,$00 ; add in carry if INK
JR Z,L2234 ; forward to CO-TEMP-7 with INK and PAPER.
SUB $02 ; reduce range $FF-$02
ADC A,$00 ; add carry if FLASH
JR Z,L2273 ; forward to CO-TEMP-C with FLASH and BRIGHT.
CP $01 ; is it 'INVERSE' ?
LD A,D ; fetch parameter for INVERSE/OVER
LD B,$01 ; prepare OVER mask setting bit 0.
JR NZ,L2228 ; forward to CO-TEMP-6 if OVER
RLCA ; shift bit 0
RLCA ; to bit 2
LD B,$04 ; set bit 2 of mask for inverse.
;; CO-TEMP-6
L2228: LD C,A ; save the A
LD A,D ; re-fetch parameter
CP $02 ; is it less than 2
JR NC,L2244 ; to REPORT-K if not 0 or 1.
; 'Invalid colour'.
LD A,C ; restore A
LD HL,$5C91 ; address system variable P_FLAG
JR L226C ; forward to exit via routine CO-CHANGE
; ---
; the branch was here with INK/PAPER and carry set for INK.
;; CO-TEMP-7
L2234: LD A,D ; fetch parameter
LD B,$07 ; set ink mask 00000111
JR C,L223E ; forward to CO-TEMP-8 with INK
RLCA ; shift bits 0-2
RLCA ; to
RLCA ; bits 3-5
LD B,$38 ; set paper mask 00111000
; both paper and ink rejoin here
;; CO-TEMP-8
L223E: LD C,A ; value to C
LD A,D ; fetch parameter
CP $0A ; is it less than 10d ?
JR C,L2246 ; forward to CO-TEMP-9 if so.
; ink 10 etc. is not allowed.
;; REPORT-K
L2244: RST 08H ; ERROR-1
DB $13 ; Error Report: Invalid colour
;; CO-TEMP-9
L2246: LD HL,$5C8F ; address system variable ATTR_T initially.
CP $08 ; compare with 8
JR C,L2258 ; forward to CO-TEMP-B with 0-7.
LD A,(HL) ; fetch temporary attribute as no change.
JR Z,L2257 ; forward to CO-TEMP-A with INK/PAPER 8
; it is either ink 9 or paper 9 (contrasting)
OR B ; or with mask to make white
CPL ; make black and change other to dark
AND $24 ; 00100100
JR Z,L2257 ; forward to CO-TEMP-A if black and
; originally light.
LD A,B ; else just use the mask (white)
;; CO-TEMP-A
L2257: LD C,A ; save A in C
;; CO-TEMP-B
L2258: LD A,C ; load colour to A
CALL L226C ; routine CO-CHANGE addressing ATTR-T
LD A,$07 ; put 7 in accumulator
CP D ; compare with parameter
SBC A,A ; $00 if 0-7, $FF if 8
CALL L226C ; routine CO-CHANGE addressing MASK-T
; mask returned in A.
; now consider P-FLAG.
RLCA ; 01110000 or 00001110
RLCA ; 11100000 or 00011100
AND $50 ; 01000000 or 00010000 (AND 01010000)
LD B,A ; transfer to mask
LD A,$08 ; load A with 8
CP D ; compare with parameter
SBC A,A ; $FF if was 9, $00 if 0-8
; continue while addressing P-FLAG
; setting bit 4 if ink 9
; setting bit 6 if paper 9
; -----------------------
; Handle change of colour
; -----------------------
; This routine addresses a system variable ATTR_T, MASK_T or P-FLAG in HL.
; colour value in A, mask in B.
;; CO-CHANGE
L226C: XOR (HL) ; impress bits specified
AND B ; by mask
XOR (HL) ; on system variable.
LD (HL),A ; update system variable.
INC HL ; address next location.
LD A,B ; put current value of mask in A
RET ; return.
; ---
; the branch was here with flash and bright
;; CO-TEMP-C
L2273: SBC A,A ; set zero flag for bright.
LD A,D ; fetch original parameter 0,1 or 8
RRCA ; rotate bit 0 to bit 7
LD B,$80 ; mask for flash 10000000
JR NZ,L227D ; forward to CO-TEMP-D if flash
RRCA ; rotate bit 7 to bit 6
LD B,$40 ; mask for bright 01000000
;; CO-TEMP-D
L227D: LD C,A ; store value in C
LD A,D ; fetch parameter
CP $08 ; compare with 8
JR Z,L2287 ; forward to CO-TEMP-E if 8
CP $02 ; test if 0 or 1
JR NC,L2244 ; back to REPORT-K if not
; 'Invalid colour'
;; CO-TEMP-E
L2287: LD A,C ; value to A
LD HL,$5C8F ; address ATTR_T
CALL L226C ; routine CO-CHANGE addressing ATTR_T
LD A,C ; fetch value
RRCA ; for flash8/bright8 complete
RRCA ; rotations to put set bit in
RRCA ; bit 7 (flash) bit 6 (bright)
JR L226C ; back to CO-CHANGE addressing MASK_T
; and indirect return.
; ---------------------
; Handle BORDER command
; ---------------------
; Command syntax example: BORDER 7
; This command routine sets the border to one of the eight colours.
; The colours used for the lower screen are based on this.
;; BORDER
L2294: CALL L1E94 ; routine FIND-INT1
CP $08 ; must be in range 0 (black) to 7 (white)
JR NC,L2244 ; back to REPORT-K if not
; 'Invalid colour'.
OUT ($FE),A ; outputting to port effects an immediate
; change.
RLCA ; shift the colour to
RLCA ; the paper bits setting the
RLCA ; ink colour black.
BIT 5,A ; is the number light coloured ?
; i.e. in the range green to white.
JR NZ,L22A6 ; skip to BORDER-1 if so
XOR $07 ; make the ink white.
;; BORDER-1
L22A6: LD ($5C48),A ; update BORDCR with new paper/ink
RET ; return.
; -----------------
; Get pixel address
; -----------------
;
;
;; PIXEL-ADD
L22AA: LD A,$AF ; load with 175 decimal.
SUB B ; subtract the y value.
JP C,L24F9 ; jump forward to REPORT-Bc if greater.
; 'Integer out of range'
; the high byte is derived from Y only.
; the first 3 bits are always 010
; the next 2 bits denote in which third of the screen the byte is.
; the last 3 bits denote in which of the 8 scan lines within a third
; the byte is located. There are 24 discrete values.
LD B,A ; the line number from top of screen to B.
AND A ; clear carry (already clear)
RRA ; 0xxxxxxx
SCF ; set carry flag
RRA ; 10xxxxxx
AND A ; clear carry flag
RRA ; 010xxxxx
XOR B ;
AND $F8 ; keep the top 5 bits 11111000
XOR B ; 010xxbbb
LD H,A ; transfer high byte to H.
; the low byte is derived from both X and Y.
LD A,C ; the x value 0-255.
RLCA ;
RLCA ;
RLCA ;
XOR B ; the y value
AND $C7 ; apply mask 11000111
XOR B ; restore unmasked bits xxyyyxxx
RLCA ; rotate to xyyyxxxx
RLCA ; required position. yyyxxxxx
LD L,A ; low byte to L.
; finally form the pixel position in A.
LD A,C ; x value to A
AND $07 ; mod 8
RET ; return
; ----------------
; Point Subroutine
; ----------------
; The point subroutine is called from s-point via the scanning functions
; table.
;; POINT-SUB
L22CB: CALL L2307 ; routine STK-TO-BC
CALL L22AA ; routine PIXEL-ADD finds address of pixel.
LD B,A ; pixel position to B, 0-7.
INC B ; increment to give rotation count 1-8.
LD A,(HL) ; fetch byte from screen.
;; POINT-LP
L22D4: RLCA ; rotate and loop back
DJNZ L22D4 ; to POINT-LP until pixel at right.
AND $01 ; test to give zero or one.
JP L2D28 ; jump forward to STACK-A to save result.
; -------------------
; Handle PLOT command
; -------------------
; Command Syntax example: PLOT 128,88
;
;; PLOT
L22DC: CALL L2307 ; routine STK-TO-BC
CALL L22E5 ; routine PLOT-SUB
JP L0D4D ; to TEMPS
; -------------------
; The Plot subroutine
; -------------------
; A screen byte holds 8 pixels so it is necessary to rotate a mask
; into the correct position to leave the other 7 pixels unaffected.
; However all 64 pixels in the character cell take any embedded colour
; items.
; A pixel can be reset (inverse 1), toggled (over 1), or set ( with inverse
; and over switches off). With both switches on, the byte is simply put
; back on the screen though the colours may change.
;; PLOT-SUB
L22E5: LD ($5C7D),BC ; store new x/y values in COORDS
CALL L22AA ; routine PIXEL-ADD gets address in HL,
; count from left 0-7 in B.
LD B,A ; transfer count to B.
INC B ; increase 1-8.
LD A,$FE ; 11111110 in A.
;; PLOT-LOOP
L22F0: RRCA ; rotate mask.
DJNZ L22F0 ; to PLOT-LOOP until B circular rotations.
LD B,A ; load mask to B
LD A,(HL) ; fetch screen byte to A
LD C,(IY+$57) ; P_FLAG to C
BIT 0,C ; is it to be OVER 1 ?
JR NZ,L22FD ; forward to PL-TST-IN if so.
; was over 0
AND B ; combine with mask to blank pixel.
;; PL-TST-IN
L22FD: BIT 2,C ; is it inverse 1 ?
JR NZ,L2303 ; to PLOT-END if so.
XOR B ; switch the pixel
CPL ; restore other 7 bits
;; PLOT-END
L2303: LD (HL),A ; load byte to the screen.
JP L0BDB ; exit to PO-ATTR to set colours for cell.
; ------------------------------
; Put two numbers in BC register
; ------------------------------
;
;
;; STK-TO-BC
L2307: CALL L2314 ; routine STK-TO-A
LD B,A ;
PUSH BC ;
CALL L2314 ; routine STK-TO-A
LD E,C ;
POP BC ;
LD D,C ;
LD C,A ;
RET ;
; -----------------------
; Put stack in A register
; -----------------------
; This routine puts the last value on the calculator stack into the accumulator
; deleting the last value.
;; STK-TO-A
L2314: CALL L2DD5 ; routine FP-TO-A compresses last value into
; accumulator. e.g. PI would become 3.
; zero flag set if positive.
JP C,L24F9 ; jump forward to REPORT-Bc if >= 255.5.
LD C,$01 ; prepare a positive sign byte.
RET Z ; return if FP-TO-BC indicated positive.
LD C,$FF ; prepare negative sign byte and
RET ; return.
; ---------------------
; Handle CIRCLE command
; ---------------------
;
; syntax has been partly checked using the class for draw command.
;; CIRCLE
L2320: RST 18H ; GET-CHAR
CP $2C ; is it required comma ?
JP NZ,L1C8A ; jump to REPORT-C if not
RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM fetches radius
CALL L1BEE ; routine CHECK-END will return here if
; nothing follows command.
RST 28H ;; FP-CALC
DB $2A ;;abs ; make radius positive
DB $3D ;;re-stack ; in full floating point form
DB $38 ;;end-calc
LD A,(HL) ; fetch first floating point byte
CP $81 ; compare to one
JR NC,L233B ; forward to C-R-GRE-1 if circle radius
; is greater than one.
RST 28H ;; FP-CALC
DB $02 ;;delete ; delete the radius from stack.
DB $38 ;;end-calc
JR L22DC ; to PLOT to just plot x,y.
; ---
;; C-R-GRE-1
L233B: RST 28H ;; FP-CALC ; x, y, r
DB $A3 ;;stk-pi/2 ; x, y, r, pi/2.
DB $38 ;;end-calc
LD (HL),$83 ; ; x, y, r, 2*PI
RST 28H ;; FP-CALC
DB $C5 ;;st-mem-5 ; store 2*PI in mem-5
DB $02 ;;delete ; x, y, z.
DB $38 ;;end-calc
CALL L247D ; routine CD-PRMS1
PUSH BC ;
RST 28H ;; FP-CALC
DB $31 ;;duplicate
DB $E1 ;;get-mem-1
DB $04 ;;multiply
DB $38 ;;end-calc
LD A,(HL) ;
CP $80 ;
JR NC,L235A ; to C-ARC-GE1
RST 28H ;; FP-CALC
DB $02 ;;delete
DB $02 ;;delete
DB $38 ;;end-calc
POP BC ;
JP L22DC ; JUMP to PLOT
; ---
;; C-ARC-GE1
L235A: RST 28H ;; FP-CALC
DB $C2 ;;st-mem-2
DB $01 ;;exchange
DB $C0 ;;st-mem-0
DB $02 ;;delete
DB $03 ;;subtract
DB $01 ;;exchange
DB $E0 ;;get-mem-0
DB $0F ;;addition
DB $C0 ;;st-mem-0
DB $01 ;;exchange
DB $31 ;;duplicate
DB $E0 ;;get-mem-0
DB $01 ;;exchange
DB $31 ;;duplicate
DB $E0 ;;get-mem-0
DB $A0 ;;stk-zero
DB $C1 ;;st-mem-1
DB $02 ;;delete
DB $38 ;;end-calc
INC (IY+$62) ; MEM-2-1st
CALL L1E94 ; routine FIND-INT1
LD L,A ;
PUSH HL ;
CALL L1E94 ; routine FIND-INT1
POP HL ;
LD H,A ;
LD ($5C7D),HL ; COORDS
POP BC ;
JP L2420 ; to DRW-STEPS
; -------------------
; Handle DRAW command
; -------------------
;
;
;; DRAW
L2382: RST 18H ; GET-CHAR
CP $2C ;
JR Z,L238D ; to DR-3-PRMS
CALL L1BEE ; routine CHECK-END
JP L2477 ; to LINE-DRAW
; ---
;; DR-3-PRMS
L238D: RST 20H ; NEXT-CHAR
CALL L1C82 ; routine EXPT-1NUM
CALL L1BEE ; routine CHECK-END
RST 28H ;; FP-CALC
DB $C5 ;;st-mem-5
DB $A2 ;;stk-half
DB $04 ;;multiply
DB $1F ;;sin
DB $31 ;;duplicate
DB $30 ;;not
DB $30 ;;not
DB $00 ;;jump-true
DB $06 ;;to L23A3, DR-SIN-NZ
DB $02 ;;delete
DB $38 ;;end-calc
JP L2477 ; to LINE-DRAW
; ---
;; DR-SIN-NZ
L23A3: DB $C0 ;;st-mem-0
DB $02 ;;delete
DB $C1 ;;st-mem-1
DB $02 ;;delete
DB $31 ;;duplicate
DB $2A ;;abs
DB $E1 ;;get-mem-1
DB $01 ;;exchange
DB $E1 ;;get-mem-1
DB $2A ;;abs
DB $0F ;;addition
DB $E0 ;;get-mem-0
DB $05 ;;division
DB $2A ;;abs
DB $E0 ;;get-mem-0
DB $01 ;;exchange
DB $3D ;;re-stack
DB $38 ;;end-calc
LD A,(HL) ;
CP $81 ;
JR NC,L23C1 ; to DR-PRMS
RST 28H ;; FP-CALC
DB $02 ;;delete
DB $02 ;;delete
DB $38 ;;end-calc
JP L2477 ; to LINE-DRAW
; ---
;; DR-PRMS
L23C1: CALL L247D ; routine CD-PRMS1
PUSH BC ;
RST 28H ;; FP-CALC
DB $02 ;;delete
DB $E1 ;;get-mem-1
DB $01 ;;exchange
DB $05 ;;division
DB $C1 ;;st-mem-1
DB $02 ;;delete
DB $01 ;;exchange
DB $31 ;;duplicate
DB $E1 ;;get-mem-1
DB $04 ;;multiply
DB $C2 ;;st-mem-2
DB $02 ;;delete
DB $01 ;;exchange
DB $31 ;;duplicate
DB $E1 ;;get-mem-1
DB $04 ;;multiply
DB $E2 ;;get-mem-2
DB $E5 ;;get-mem-5
DB $E0 ;;get-mem-0
DB $03 ;;subtract
DB $A2 ;;stk-half
DB $04 ;;multiply
DB $31 ;;duplicate
DB $1F ;;sin
DB $C5 ;;st-mem-5
DB $02 ;;delete
DB $20 ;;cos
DB $C0 ;;st-mem-0
DB $02 ;;delete
DB $C2 ;;st-mem-2
DB $02 ;;delete
DB $C1 ;;st-mem-1
DB $E5 ;;get-mem-5
DB $04 ;;multiply
DB $E0 ;;get-mem-0
DB $E2 ;;get-mem-2
DB $04 ;;multiply
DB $0F ;;addition
DB $E1 ;;get-mem-1
DB $01 ;;exchange
DB $C1 ;;st-mem-1
DB $02 ;;delete
DB $E0 ;;get-mem-0
DB $04 ;;multiply
DB $E2 ;;get-mem-2
DB $E5 ;;get-mem-5
DB $04 ;;multiply
DB $03 ;;subtract
DB $C2 ;;st-mem-2
DB $2A ;;abs
DB $E1 ;;get-mem-1
DB $2A ;;abs
DB $0F ;;addition
DB $02 ;;delete
DB $38 ;;end-calc
LD A,(DE) ;
CP $81 ;
POP BC ;
JP C,L2477 ; to LINE-DRAW
PUSH BC ;
RST 28H ;; FP-CALC
DB $01 ;;exchange
DB $38 ;;end-calc
LD A,($5C7D) ; COORDS-x
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $C0 ;;st-mem-0
DB $0F ;;addition
DB $01 ;;exchange
DB $38 ;;end-calc
LD A,($5C7E) ; COORDS-y
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $C5 ;;st-mem-5
DB $0F ;;addition
DB $E0 ;;get-mem-0
DB $E5 ;;get-mem-5
DB $38 ;;end-calc
POP BC ;
;; DRW-STEPS
L2420: DEC B ;
JR Z,L245F ; to ARC-END
JR L2439 ; to ARC-START
; ---
;; ARC-LOOP
L2425: RST 28H ;; FP-CALC
DB $E1 ;;get-mem-1
DB $31 ;;duplicate
DB $E3 ;;get-mem-3
DB $04 ;;multiply
DB $E2 ;;get-mem-2
DB $E4 ;;get-mem-4
DB $04 ;;multiply
DB $03 ;;subtract
DB $C1 ;;st-mem-1
DB $02 ;;delete
DB $E4 ;;get-mem-4
DB $04 ;;multiply
DB $E2 ;;get-mem-2
DB $E3 ;;get-mem-3
DB $04 ;;multiply
DB $0F ;;addition
DB $C2 ;;st-mem-2
DB $02 ;;delete
DB $38 ;;end-calc
;; ARC-START
L2439: PUSH BC ;
RST 28H ;; FP-CALC
DB $C0 ;;st-mem-0
DB $02 ;;delete
DB $E1 ;;get-mem-1
DB $0F ;;addition
DB $31 ;;duplicate
DB $38 ;;end-calc
LD A,($5C7D) ; COORDS-x
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $03 ;;subtract
DB $E0 ;;get-mem-0
DB $E2 ;;get-mem-2
DB $0F ;;addition
DB $C0 ;;st-mem-0
DB $01 ;;exchange
DB $E0 ;;get-mem-0
DB $38 ;;end-calc
LD A,($5C7E) ; COORDS-y
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $03 ;;subtract
DB $38 ;;end-calc
CALL L24B7 ; routine DRAW-LINE
POP BC ;
DJNZ L2425 ; to ARC-LOOP
;; ARC-END
L245F: RST 28H ;; FP-CALC
DB $02 ;;delete
DB $02 ;;delete
DB $01 ;;exchange
DB $38 ;;end-calc
LD A,($5C7D) ; COORDS-x
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $03 ;;subtract
DB $01 ;;exchange
DB $38 ;;end-calc
LD A,($5C7E) ; COORDS-y
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $03 ;;subtract
DB $38 ;;end-calc
;; LINE-DRAW
L2477: CALL L24B7 ; routine DRAW-LINE
JP L0D4D ; to TEMPS
; ------------------
; Initial parameters
; ------------------
;
;
;; CD-PRMS1
L247D: RST 28H ;; FP-CALC
DB $31 ;;duplicate
DB $28 ;;sqr
DB $34 ;;stk-data
DB $32 ;;Exponent: $82, Bytes: 1
DB $00 ;;(+00,+00,+00)
DB $01 ;;exchange
DB $05 ;;division
DB $E5 ;;get-mem-5
DB $01 ;;exchange
DB $05 ;;division
DB $2A ;;abs
DB $38 ;;end-calc
CALL L2DD5 ; routine FP-TO-A
JR C,L2495 ; to USE-252
AND $FC ;
ADD A,$04 ;
JR NC,L2497 ; to DRAW-SAVE
;; USE-252
L2495: LD A,$FC ;
;; DRAW-SAVE
L2497: PUSH AF ;
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $E5 ;;get-mem-5
DB $01 ;;exchange
DB $05 ;;division
DB $31 ;;duplicate
DB $1F ;;sin
DB $C4 ;;st-mem-4
DB $02 ;;delete
DB $31 ;;duplicate
DB $A2 ;;stk-half
DB $04 ;;multiply
DB $1F ;;sin
DB $C1 ;;st-mem-1
DB $01 ;;exchange
DB $C0 ;;st-mem-0
DB $02 ;;delete
DB $31 ;;duplicate
DB $04 ;;multiply
DB $31 ;;duplicate
DB $0F ;;addition
DB $A1 ;;stk-one
DB $03 ;;subtract
DB $1B ;;negate
DB $C3 ;;st-mem-3
DB $02 ;;delete
DB $38 ;;end-calc
POP BC ;
RET ;
; ------------
; Line drawing
; ------------
;
;
;; DRAW-LINE
L24B7: CALL L2307 ; routine STK-TO-BC
LD A,C ;
CP B ;
JR NC,L24C4 ; to DL-X-GE-Y
LD L,C ;
PUSH DE ;
XOR A ;
LD E,A ;
JR L24CB ; to DL-LARGER
; ---
;; DL-X-GE-Y
L24C4: OR C ;
RET Z ;
LD L,B ;
LD B,C ;
PUSH DE ;
LD D,$00 ;
;; DL-LARGER
L24CB: LD H,B ;
LD A,B ;
RRA ;
;; D-L-LOOP
L24CE: ADD A,L ;
JR C,L24D4 ; to D-L-DIAG
CP H ;
JR C,L24DB ; to D-L-HR-VT
;; D-L-DIAG
L24D4: SUB H ;
LD C,A ;
EXX ;
POP BC ;
PUSH BC ;
JR L24DF ; to D-L-STEP
; ---
;; D-L-HR-VT
L24DB: LD C,A ;
PUSH DE ;
EXX ;
POP BC ;
;; D-L-STEP
L24DF: LD HL,($5C7D) ; COORDS
LD A,B ;
ADD A,H ;
LD B,A ;
LD A,C ;
INC A ;
ADD A,L ;
JR C,L24F7 ; to D-L-RANGE
JR Z,L24F9 ; to REPORT-Bc
;; D-L-PLOT
L24EC: DEC A ;
LD C,A ;
CALL L22E5 ; routine PLOT-SUB
EXX ;
LD A,C ;
DJNZ L24CE ; to D-L-LOOP
POP DE ;
RET ;
; ---
;; D-L-RANGE
L24F7: JR Z,L24EC ; to D-L-PLOT
;; REPORT-Bc
L24F9: RST 08H ; ERROR-1
DB $0A ; Error Report: Integer out of range
;***********************************
;** Part 8. EXPRESSION EVALUATION **
;***********************************
;
; It is a this stage of the ROM that the Spectrum ceases altogether to be
; just a colourful novelty. One remarkable feature is that in all previous
; commands when the Spectrum is expecting a number or a string then an
; expression of the same type can be substituted ad infinitum.
; This is the routine that evaluates that expression.
; This is what causes 2 + 2 to give the answer 4.
; That is quite easy to understand. However you don't have to make it much
; more complex to start a remarkable juggling act.
; e.g. PRINT 2 * (VAL "2+2" + TAN 3)
; In fact, provided there is enough free RAM, the Spectrum can evaluate
; an expression of unlimited complexity.
; Apart from a couple of minor glitches, which you can now correct, the
; system is remarkably robust.
; ---------------------------------
; Scan expression or sub-expression
; ---------------------------------
;
;
;; SCANNING
L24FB: RST 18H ; GET-CHAR
LD B,$00 ; priority marker zero is pushed on stack
; to signify end of expression when it is
; popped off again.
PUSH BC ; put in on stack.
; and proceed to consider the first character
; of the expression.
;; S-LOOP-1
L24FF: LD C,A ; store the character while a look up is done.
LD HL,L2596 ; Address: scan-func
CALL L16DC ; routine INDEXER is called to see if it is
; part of a limited range '+', '(', 'ATTR' etc.
LD A,C ; fetch the character back
JP NC,L2684 ; jump forward to S-ALPHNUM if not in primary
; operators and functions to consider in the
; first instance a digit or a variable and
; then anything else. >>>
LD B,$00 ; but here if it was found in table so
LD C,(HL) ; fetch offset from table and make B zero.
ADD HL,BC ; add the offset to position found
JP (HL) ; and jump to the routine e.g. S-BIN
; making an indirect exit from there.
; -------------------------------------------------------------------------
; The four service subroutines for routines in the scannings function table
; -------------------------------------------------------------------------
; PRINT """Hooray!"" he cried."
;; S-QUOTE-S
L250F: CALL L0074 ; routine CH-ADD+1 points to next character
; and fetches that character.
INC BC ; increase length counter.
CP $0D ; is it carriage return ?
; inside a quote.
JP Z,L1C8A ; jump back to REPORT-C if so.
; 'Nonsense in BASIC'.
CP $22 ; is it a quote '"' ?
JR NZ,L250F ; back to S-QUOTE-S if not for more.
CALL L0074 ; routine CH-ADD+1
CP $22 ; compare with possible adjacent quote
RET ; return. with zero set if two together.
; ---
; This subroutine is used to get two coordinate expressions for the three
; functions SCREEN$, ATTR and POINT that have two fixed parameters and
; therefore require surrounding braces.
;; S-2-COORD
L2522: RST 20H ; NEXT-CHAR
CP $28 ; is it the opening '(' ?
JR NZ,L252D ; forward to S-RPORT-C if not
; 'Nonsense in BASIC'.
CALL L1C79 ; routine NEXT-2NUM gets two comma-separated
; numeric expressions. Note. this could cause
; many more recursive calls to SCANNING but
; the parent function will be evaluated fully
; before rejoining the main juggling act.
RST 18H ; GET-CHAR
CP $29 ; is it the closing ')' ?
;; S-RPORT-C
L252D: JP NZ,L1C8A ; jump back to REPORT-C if not.
; 'Nonsense in BASIC'.
; ------------
; Check syntax
; ------------
; This routine is called on a number of occasions to check if syntax is being
; checked or if the program is being run. To test the flag inline would use
; four bytes of code, but a call instruction only uses 3 bytes of code.
;; SYNTAX-Z
L2530: BIT 7,(IY+$01) ; test FLAGS - checking syntax only ?
RET ; return.
; ----------------
; Scanning SCREEN$
; ----------------
; This function returns the code of a bit-mapped character at screen
; position at line C, column B. It is unable to detect the mosaic characters
; which are not bit-mapped but detects the ASCII 32 - 127 range.
; The bit-mapped UDGs are ignored which is curious as it requires only a
; few extra bytes of code. As usual, anything to do with CHARS is weird.
; If no match is found a null string is returned.
; No actual check on ranges is performed - that's up to the BASIC programmer.
; No real harm can come from SCREEN$(255,255) although the BASIC manual
; says that invalid values will be trapped.
; Interestingly, in the Pitman pocket guide, 1984, Vickers says that the
; range checking will be performed.
;; S-SCRN$-S
L2535: CALL L2307 ; routine STK-TO-BC.
LD HL,($5C36) ; fetch address of CHARS.
LD DE,$0100 ; fetch offset to chr$ 32
ADD HL,DE ; and find start of bitmaps.
; Note. not inc h. ??
LD A,C ; transfer line to A.
RRCA ; multiply
RRCA ; by
RRCA ; thirty-two.
AND $E0 ; and with 11100000
XOR B ; combine with column $00 - $1F
LD E,A ; to give the low byte of top line
LD A,C ; column to A range 00000000 to 00011111
AND $18 ; and with 00011000
XOR $40 ; xor with 01000000 (high byte screen start)
LD D,A ; register DE now holds start address of cell.
LD B,$60 ; there are 96 characters in ASCII set.
;; S-SCRN-LP
L254F: PUSH BC ; save count
PUSH DE ; save screen start address
PUSH HL ; save bitmap start
LD A,(DE) ; first byte of screen to A
XOR (HL) ; xor with corresponding character byte
JR Z,L255A ; forward to S-SC-MTCH if they match
; if inverse result would be $FF
; if any other then mismatch
INC A ; set to $00 if inverse
JR NZ,L2573 ; forward to S-SCR-NXT if a mismatch
DEC A ; restore $FF
; a match has been found so seven more to test.
;; S-SC-MTCH
L255A: LD C,A ; load C with inverse mask $00 or $FF
LD B,$07 ; count seven more bytes
;; S-SC-ROWS
L255D: INC D ; increment screen address.
INC HL ; increment bitmap address.
LD A,(DE) ; byte to A
XOR (HL) ; will give $00 or $FF (inverse)
XOR C ; xor with inverse mask
JR NZ,L2573 ; forward to S-SCR-NXT if no match.
DJNZ L255D ; back to S-SC-ROWS until all eight matched.
; continue if a match of all eight bytes was found
POP BC ; discard the
POP BC ; saved
POP BC ; pointers
LD A,$80 ; the endpoint of character set
SUB B ; subtract the counter
; to give the code 32-127
LD BC,$0001 ; make one space in workspace.
RST 30H ; BC-SPACES creates the space sliding
; the calculator stack upwards.
LD (DE),A ; start is addressed by DE, so insert code
JR L257D ; forward to S-SCR-STO
; ---
; the jump was here if no match and more bitmaps to test.
;; S-SCR-NXT
L2573: POP HL ; restore the last bitmap start
LD DE,$0008 ; and prepare to add 8.
ADD HL,DE ; now addresses next character bitmap.
POP DE ; restore screen address
POP BC ; and character counter in B
DJNZ L254F ; back to S-SCRN-LP if more characters.
LD C,B ; B is now zero, so BC now zero.
;; S-SCR-STO
L257D: JP L2AB2 ; to STK-STO-$ to store the string in
; workspace or a string with zero length.
; (value of DE doesn't matter in last case)
; Note. this exit seems correct but the general-purpose routine S-STRING
; that calls this one will also stack any of its string results so this
; leads to a double storing of the result in this case.
; The instruction at L257D should just be a RET.
; credit Stephen Kelly and others, 1982.
; -------------
; Scanning ATTR
; -------------
; This function subroutine returns the attributes of a screen location -
; a numeric result.
; Again it's up to the BASIC programmer to supply valid values of line/column.
;; S-ATTR-S
L2580: CALL L2307 ; routine STK-TO-BC fetches line to C,
; and column to B.
LD A,C ; line to A $00 - $17 (max 00010111)
RRCA ; rotate
RRCA ; bits
RRCA ; left.
LD C,A ; store in C as an intermediate value.
AND $E0 ; pick up bits 11100000 ( was 00011100 )
XOR B ; combine with column $00 - $1F
LD L,A ; low byte now correct.
LD A,C ; bring back intermediate result from C
AND $03 ; mask to give correct third of
; screen $00 - $02
XOR $58 ; combine with base address.
LD H,A ; high byte correct.
LD A,(HL) ; pick up the colour attribute.
JP L2D28 ; forward to STACK-A to store result
; and make an indirect exit.
; -----------------------
; Scanning function table
; -----------------------
; This table is used by INDEXER routine to find the offsets to
; four operators and eight functions. e.g. $A8 is the token 'FN'.
; This table is used in the first instance for the first character of an
; expression or by a recursive call to SCANNING for the first character of
; any sub-expression. It eliminates functions that have no argument or
; functions that can have more than one argument and therefore require
; braces. By eliminating and dealing with these now it can later take a
; simplistic approach to all other functions and assume that they have
; one argument.
; Similarly by eliminating BIN and '.' now it is later able to assume that
; all numbers begin with a digit and that the presence of a number or
; variable can be detected by a call to ALPHANUM.
; By default all expressions are positive and the spurious '+' is eliminated
; now as in print +2. This should not be confused with the operator '+'.
; Note. this does allow a degree of nonsense to be accepted as in
; PRINT +"3 is the greatest.".
; An acquired programming skill is the ability to include brackets where
; they are not necessary.
; A bracket at the start of a sub-expression may be spurious or necessary
; to denote that the contained expression is to be evaluated as an entity.
; In either case this is dealt with by recursive calls to SCANNING.
; An expression that begins with a quote requires special treatment.
;; scan-func
L2596: DB $22, L25B3-$-1 ; $1C offset to S-QUOTE
DB '(', L25E8-$-1 ; $4F offset to S-BRACKET
DB '.', L268D-$-1 ; $F2 offset to S-DECIMAL
DB '+', L25AF-$-1 ; $12 offset to S-U-PLUS
DB $A8, L25F5-$-1 ; $56 offset to S-FN
DB $A5, L25F8-$-1 ; $57 offset to S-RND
DB $A7, L2627-$-1 ; $84 offset to S-PI
DB $A6, L2634-$-1 ; $8F offset to S-INKEY$
DB $C4, L268D-$-1 ; $E6 offset to S-BIN
DB $AA, L2668-$-1 ; $BF offset to S-SCREEN$
DB $AB, L2672-$-1 ; $C7 offset to S-ATTR
DB $A9, L267B-$-1 ; $CE offset to S-POINT
DB $00 ; zero end marker
; --------------------------
; Scanning function routines
; --------------------------
; These are the 11 subroutines accessed by the above table.
; S-BIN and S-DECIMAL are the same
; The 1-byte offset limits their location to within 255 bytes of their
; entry in the table.
; ->
;; S-U-PLUS
L25AF: RST 20H ; NEXT-CHAR just ignore
JP L24FF ; to S-LOOP-1
; ---
; ->
;; S-QUOTE
L25B3: RST 18H ; GET-CHAR
INC HL ; address next character (first in quotes)
PUSH HL ; save start of quoted text.
LD BC,$0000 ; initialize length of string to zero.
CALL L250F ; routine S-QUOTE-S
JR NZ,L25D9 ; forward to S-Q-PRMS if
;; S-Q-AGAIN
L25BE: CALL L250F ; routine S-QUOTE-S copies string until a
; quote is encountered
JR Z,L25BE ; back to S-Q-AGAIN if two quotes WERE
; together.
; but if just an isolated quote then that terminates the string.
CALL L2530 ; routine SYNTAX-Z
JR Z,L25D9 ; forward to S-Q-PRMS if checking syntax.
RST 30H ; BC-SPACES creates the space for true
; copy of string in workspace.
POP HL ; re-fetch start of quoted text.
PUSH DE ; save start in workspace.
;; S-Q-COPY
L25CB: LD A,(HL) ; fetch a character from source.
INC HL ; advance source address.
LD (DE),A ; place in destination.
INC DE ; advance destination address.
CP $22 ; was it a '"' just copied ?
JR NZ,L25CB ; back to S-Q-COPY to copy more if not
LD A,(HL) ; fetch adjacent character from source.
INC HL ; advance source address.
CP $22 ; is this '"' ? - i.e. two quotes together ?
JR Z,L25CB ; to S-Q-COPY if so including just one of the
; pair of quotes.
; proceed when terminating quote encountered.
;; S-Q-PRMS
L25D9: DEC BC ; decrease count by 1.
POP DE ; restore start of string in workspace.
;; S-STRING
L25DB: LD HL,$5C3B ; Address FLAGS system variable.
RES 6,(HL) ; signal string result.
BIT 7,(HL) ; is syntax being checked.
CALL NZ,L2AB2 ; routine STK-STO-$ is called in runtime.
JP L2712 ; jump forward to S-CONT-2 ===>
; ---
; ->
;; S-BRACKET
L25E8: RST 20H ; NEXT-CHAR
CALL L24FB ; routine SCANNING is called recursively.
CP $29 ; is it the closing ')' ?
JP NZ,L1C8A ; jump back to REPORT-C if not
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR
JP L2712 ; jump forward to S-CONT-2 ===>
; ---
; ->
;; S-FN
L25F5: JP L27BD ; jump forward to S-FN-SBRN.
; ---
; ->
;; S-RND
L25F8: CALL L2530 ; routine SYNTAX-Z
JR Z,L2625 ; forward to S-RND-END if checking syntax.
LD BC,($5C76) ; fetch system variable SEED
CALL L2D2B ; routine STACK-BC places on calculator stack
RST 28H ;; FP-CALC ;s.
DB $A1 ;;stk-one ;s,1.
DB $0F ;;addition ;s+1.
DB $34 ;;stk-data ;
DB $37 ;;Exponent: $87,
;;Bytes: 1
DB $16 ;;(+00,+00,+00) ;s+1,75.
DB $04 ;;multiply ;(s+1)*75 = v
DB $34 ;;stk-data ;v.
DB $80 ;;Bytes: 3
DB $41 ;;Exponent $91
DB $00,$00,$80 ;;(+00) ;v,65537.
DB $32 ;;n-mod-m ;remainder, result.
DB $02 ;;delete ;remainder.
DB $A1 ;;stk-one ;remainder, 1.
DB $03 ;;subtract ;remainder - 1. = rnd
DB $31 ;;duplicate ;rnd,rnd.
DB $38 ;;end-calc
CALL L2DA2 ; routine FP-TO-BC
LD ($5C76),BC ; store in SEED for next starting point.
LD A,(HL) ; fetch exponent
AND A ; is it zero ?
JR Z,L2625 ; forward if so to S-RND-END
SUB $10 ; reduce exponent by 2^16
LD (HL),A ; place back
;; S-RND-END
L2625: JR L2630 ; forward to S-PI-END
; ---
; the number PI 3.14159...
; ->
;; S-PI
L2627: CALL L2530 ; routine SYNTAX-Z
JR Z,L2630 ; to S-PI-END if checking syntax.
RST 28H ;; FP-CALC
DB $A3 ;;stk-pi/2 pi/2.
DB $38 ;;end-calc
INC (HL) ; increment the exponent leaving pi
; on the calculator stack.
;; S-PI-END
L2630: RST 20H ; NEXT-CHAR
JP L26C3 ; jump forward to S-NUMERIC
; ---
; ->
;; S-INKEY$
L2634: LD BC,$105A ; priority $10, operation code $1A ('read-in')
; +$40 for string result, numeric operand.
; set this up now in case we need to use the
; calculator.
RST 20H ; NEXT-CHAR
CP $23 ; '#' ?
JP Z,L270D ; to S-PUSH-PO if so to use the calculator
; single operation
; to read from network/RS232 etc. .
; else read a key from the keyboard.
LD HL,$5C3B ; fetch FLAGS
RES 6,(HL) ; signal string result.
BIT 7,(HL) ; checking syntax ?
JR Z,L2665 ; forward to S-INK$-EN if so
;===============================
IF BAS48_ONLY=1
CALL L028E
ELSE
JP L3B6C ; Spectrum 128 patch
ENDIF
;===============================
L2649: LD C,$00 ; the length of an empty string
JR NZ,L2660 ; to S-IK$-STK to store empty string if
; no key returned.
CALL L031E ; routine K-TEST get main code in A
JR NC,L2660 ; to S-IK$-STK to stack null string if
; invalid
DEC D ; D is expected to be FLAGS so set bit 3 $FF
; 'L' Mode so no keywords.
LD E,A ; main key to A
; C is MODE 0 'KLC' from above still.
CALL L0333 ; routine K-DECODE
L2657: PUSH AF ; save the code
LD BC,$0001 ; make room for one character
RST 30H ; BC-SPACES
POP AF ; bring the code back
LD (DE),A ; put the key in workspace
LD C,$01 ; set C length to one
;; S-IK$-STK
L2660: LD B,$00 ; set high byte of length to zero
CALL L2AB2 ; routine STK-STO-$
;; S-INK$-EN
L2665: JP L2712 ; to S-CONT-2 ===>
; ---
; ->
;; S-SCREEN$
L2668: CALL L2522 ; routine S-2-COORD
CALL NZ,L2535 ; routine S-SCRN$-S
RST 20H ; NEXT-CHAR
JP L25DB ; forward to S-STRING to stack result
; ---
; ->
;; S-ATTR
L2672: CALL L2522 ; routine S-2-COORD
CALL NZ,L2580 ; routine S-ATTR-S
RST 20H ; NEXT-CHAR
JR L26C3 ; forward to S-NUMERIC
; ---
; ->
;; S-POINT
L267B: CALL L2522 ; routine S-2-COORD
CALL NZ,L22CB ; routine POINT-SUB
RST 20H ; NEXT-CHAR
JR L26C3 ; forward to S-NUMERIC
; -----------------------------
; ==> The branch was here if not in table.
;; S-ALPHNUM
L2684: CALL L2C88 ; routine ALPHANUM checks if variable or
; a digit.
JR NC,L26DF ; forward to S-NEGATE if not to consider
; a '-' character then functions.
CP $41 ; compare 'A'
JR NC,L26C9 ; forward to S-LETTER if alpha ->
; else must have been numeric so continue
; into that routine.
; This important routine is called during runtime and from LINE-SCAN
; when a BASIC line is checked for syntax. It is this routine that
; inserts, during syntax checking, the invisible floating point numbers
; after the numeric expression. During runtime it just picks these
; numbers up. It also handles BIN format numbers.
; ->
;; S-BIN
;; S-DECIMAL
L268D: CALL L2530 ; routine SYNTAX-Z
JR NZ,L26B5 ; to S-STK-DEC in runtime
; this route is taken when checking syntax.
CALL L2C9B ; routine DEC-TO-FP to evaluate number
RST 18H ; GET-CHAR to fetch HL
LD BC,$0006 ; six locations required
CALL L1655 ; routine MAKE-ROOM
INC HL ; to first new location
LD (HL),$0E ; insert number marker
INC HL ; address next
EX DE,HL ; make DE destination.
LD HL,($5C65) ; STKEND points to end of stack.
LD C,$05 ; result is five locations lower
AND A ; prepare for true subtraction
SBC HL,BC ; point to start of value.
LD ($5C65),HL ; update STKEND as we are taking number.
LDIR ; Copy five bytes to program location
EX DE,HL ; transfer pointer to HL
DEC HL ; adjust
CALL L0077 ; routine TEMP-PTR1 sets CH-ADD
JR L26C3 ; to S-NUMERIC to record nature of result
; ---
; branch here in runtime.
;; S-STK-DEC
L26B5: RST 18H ; GET-CHAR positions HL at digit.
;; S-SD-SKIP
L26B6: INC HL ; advance pointer
LD A,(HL) ; until we find
CP $0E ; chr 14d - the number indicator
JR NZ,L26B6 ; to S-SD-SKIP until a match
; it has to be here.
INC HL ; point to first byte of number
CALL L33B4 ; routine STACK-NUM stacks it
LD ($5C5D),HL ; update system variable CH_ADD
;; S-NUMERIC
L26C3: SET 6,(IY+$01) ; update FLAGS - Signal numeric result
JR L26DD ; forward to S-CONT-1 ===>
; actually S-CONT-2 is destination but why
; waste a byte on a jump when a JR will do.
; actually a JR L2712 can be used. Rats.
; end of functions accessed from scanning functions table.
; --------------------------
; Scanning variable routines
; --------------------------
;
;
;; S-LETTER
L26C9: CALL L28B2 ; routine LOOK-VARS
JP C,L1C2E ; jump back to REPORT-2 if not found
; 'Variable not found'
; but a variable is always 'found' if syntax
; is being checked.
CALL Z,L2996 ; routine STK-VAR considers a subscript/slice
LD A,($5C3B) ; fetch FLAGS value
CP $C0 ; compare 11000000
JR C,L26DD ; step forward to S-CONT-1 if string ===>
INC HL ; advance pointer
CALL L33B4 ; routine STACK-NUM
;; S-CONT-1
L26DD: JR L2712 ; forward to S-CONT-2 ===>
; ----------------------------------------
; -> the scanning branch was here if not alphanumeric.
; All the remaining functions will be evaluated by a single call to the
; calculator. The correct priority for the operation has to be placed in
; the B register and the operation code, calculator literal in the C register.
; the operation code has bit 7 set if result is numeric and bit 6 is
; set if operand is numeric. so
; $C0 = numeric result, numeric operand. e.g. 'sin'
; $80 = numeric result, string operand. e.g. 'code'
; $40 = string result, numeric operand. e.g. 'str$'
; $00 = string result, string operand. e.g. 'val$'
;; S-NEGATE
L26DF: LD BC,$09DB ; prepare priority 09, operation code $C0 +
; 'negate' ($1B) - bits 6 and 7 set for numeric
; result and numeric operand.
CP $2D ; is it '-' ?
JR Z,L270D ; forward if so to S-PUSH-PO
LD BC,$1018 ; prepare priority $10, operation code 'val$' -
; bits 6 and 7 reset for string result and
; string operand.
CP $AE ; is it 'VAL$' ?
JR Z,L270D ; forward if so to S-PUSH-PO
SUB $AF ; subtract token 'CODE' value to reduce
; functions 'CODE' to 'NOT' although the
; upper range is, as yet, unchecked.
; valid range would be $00 - $14.
JP C,L1C8A ; jump back to REPORT-C with anything else
; 'Nonsense in BASIC'
LD BC,$04F0 ; prepare priority $04, operation $C0 +
; 'not' ($30)
CP $14 ; is it 'NOT'
JR Z,L270D ; forward to S-PUSH-PO if so
JP NC,L1C8A ; to REPORT-C if higher
; 'Nonsense in BASIC'
LD B,$10 ; priority $10 for all the rest
ADD A,$DC ; make range $DC - $EF
; $C0 + 'code'($1C) thru 'chr$' ($2F)
LD C,A ; transfer 'function' to C
CP $DF ; is it 'sin' ?
JR NC,L2707 ; forward to S-NO-TO-$ with 'sin' through
; 'chr$' as operand is numeric.
; all the rest 'cos' through 'chr$' give a numeric result except 'str$'
; and 'chr$'.
RES 6,C ; signal string operand for 'code', 'val' and
; 'len'.
;; S-NO-TO-$
L2707: CP $EE ; compare 'str$'
JR C,L270D ; forward to S-PUSH-PO if lower as result
; is numeric.
RES 7,C ; reset bit 7 of op code for 'str$', 'chr$'
; as result is string.
; >> This is where they were all headed for.
;; S-PUSH-PO
L270D: PUSH BC ; push the priority and calculator operation
; code.
RST 20H ; NEXT-CHAR
JP L24FF ; jump back to S-LOOP-1 to go round the loop
; again with the next character.
; --------------------------------
; ===> there were many branches forward to here
;; S-CONT-2
L2712: RST 18H ; GET-CHAR
;; S-CONT-3
L2713: CP $28 ; is it '(' ?
JR NZ,L2723 ; forward to S-OPERTR if not >
BIT 6,(IY+$01) ; test FLAGS - numeric or string result ?
JR NZ,L2734 ; forward to S-LOOP if numeric to evaluate >
; if a string preceded '(' then slice it.
CALL L2A52 ; routine SLICING
RST 20H ; NEXT-CHAR
JR L2713 ; back to S-CONT-3
; ---------------------------
; the branch was here when possibility of an operator '(' has been excluded.
;; S-OPERTR
L2723: LD B,$00 ; prepare to add
LD C,A ; possible operator to C
LD HL,L2795 ; Address: $2795 - tbl-of-ops
CALL L16DC ; routine INDEXER
JR NC,L2734 ; forward to S-LOOP if not in table
; but if found in table the priority has to be looked up.
LD C,(HL) ; operation code to C ( B is still zero )
LD HL,L27B0 - $C3 ; $26ED is base of table
ADD HL,BC ; index into table.
LD B,(HL) ; priority to B.
; ------------------
; Scanning main loop
; ------------------
; the juggling act
;; S-LOOP
L2734: POP DE ; fetch last priority and operation
LD A,D ; priority to A
CP B ; compare with this one
JR C,L2773 ; forward to S-TIGHTER to execute the
; last operation before this one as it has
; higher priority.
; the last priority was greater or equal this one.
AND A ; if it is zero then so is this
JP Z,L0018 ; jump to exit via get-char pointing at
; next character.
; This may be the character after the
; expression or, if exiting a recursive call,
; the next part of the expression to be
; evaluated.
PUSH BC ; save current priority/operation
; as it has lower precedence than the one
; now in DE.
; the 'USR' function is special in that it is overloaded to give two types
; of result.
LD HL,$5C3B ; address FLAGS
LD A,E ; new operation to A register
CP $ED ; is it $C0 + 'usr-no' ($2D) ?
JR NZ,L274C ; forward to S-STK-LST if not
BIT 6,(HL) ; string result expected ?
; (from the lower priority operand we've
; just pushed on stack )
JR NZ,L274C ; forward to S-STK-LST if numeric
; as operand bits match.
LD E,$99 ; reset bit 6 and substitute $19 'usr-$'
; for string operand.
;; S-STK-LST
L274C: PUSH DE ; now stack this priority/operation
CALL L2530 ; routine SYNTAX-Z
JR Z,L275B ; forward to S-SYNTEST if checking syntax.
LD A,E ; fetch the operation code
AND $3F ; mask off the result/operand bits to leave
; a calculator literal.
LD B,A ; transfer to B register
; now use the calculator to perform the single operation - operand is on
; the calculator stack.
; Note. although the calculator is performing a single operation most
; functions e.g. TAN are written using other functions and literals and
; these in turn are written using further strings of calculator literals so
; another level of magical recursion joins the juggling act for a while
; as the calculator too is calling itself.
RST 28H ;; FP-CALC
DB $3B ;;fp-calc-2
L2758: DB $38 ;;end-calc
JR L2764 ; forward to S-RUNTEST
; ---
; the branch was here if checking syntax only.
;; S-SYNTEST
L275B: LD A,E ; fetch the operation code to accumulator
XOR (IY+$01) ; compare with bits of FLAGS
AND $40 ; bit 6 will be zero now if operand
; matched expected result.
;; S-RPORT-C2
L2761: JP NZ,L1C8A ; to REPORT-C if mismatch
; 'Nonsense in BASIC'
; else continue to set flags for next
; the branch is to here in runtime after a successful operation.
;; S-RUNTEST
L2764: POP DE ; fetch the last operation from stack
LD HL,$5C3B ; address FLAGS
SET 6,(HL) ; set default to numeric result in FLAGS
BIT 7,E ; test the operational result
JR NZ,L2770 ; forward to S-LOOPEND if numeric
RES 6,(HL) ; reset bit 6 of FLAGS to show string result.
;; S-LOOPEND
L2770: POP BC ; fetch the previous priority/operation
JR L2734 ; back to S-LOOP to perform these
; ---
; the branch was here when a stacked priority/operator had higher priority
; than the current one.
;; S-TIGHTER
L2773: PUSH DE ; save high priority op on stack again
LD A,C ; fetch lower priority operation code
BIT 6,(IY+$01) ; test FLAGS - Numeric or string result ?
JR NZ,L2790 ; forward to S-NEXT if numeric result
; if this is lower priority yet has string then must be a comparison.
; Since these can only be evaluated in context and were defaulted to
; numeric in operator look up they must be changed to string equivalents.
AND $3F ; mask to give true calculator literal
ADD A,$08 ; augment numeric literals to string
; equivalents.
; 'no-&-no' => 'str-&-no'
; 'no-l-eql' => 'str-l-eql'
; 'no-gr-eq' => 'str-gr-eq'
; 'nos-neql' => 'strs-neql'
; 'no-grtr' => 'str-grtr'
; 'no-less' => 'str-less'
; 'nos-eql' => 'strs-eql'
; 'addition' => 'strs-add'
LD C,A ; put modified comparison operator back
CP $10 ; is it now 'str-&-no' ?
JR NZ,L2788 ; forward to S-NOT-AND if not.
SET 6,C ; set numeric operand bit
JR L2790 ; forward to S-NEXT
; ---
;; S-NOT-AND
L2788: JR C,L2761 ; back to S-RPORT-C2 if less
; 'Nonsense in BASIC'.
; e.g. a$ * b$
CP $17 ; is it 'strs-add' ?
JR Z,L2790 ; forward to to S-NEXT if so
; (bit 6 and 7 are reset)
SET 7,C ; set numeric (Boolean) result for all others
;; S-NEXT
L2790: PUSH BC ; now save this priority/operation on stack
RST 20H ; NEXT-CHAR
JP L24FF ; jump back to S-LOOP-1
; ------------------
; Table of operators
; ------------------
; This table is used to look up the calculator literals associated with
; the operator character. The thirteen calculator operations $03 - $0F
; have bits 6 and 7 set to signify a numeric result.
; Some of these codes and bits may be altered later if the context suggests
; a string comparison or operation.
; that is '+', '=', '>', '<', '<=', '>=' or '<>'.
;; tbl-of-ops
L2795: DB '+', $CF ; $C0 + 'addition'
DB '-', $C3 ; $C0 + 'subtract'
DB '*', $C4 ; $C0 + 'multiply'
DB '/', $C5 ; $C0 + 'division'
DB '^', $C6 ; $C0 + 'to-power'
DB '=', $CE ; $C0 + 'nos-eql'
DB '>', $CC ; $C0 + 'no-grtr'
DB '<', $CD ; $C0 + 'no-less'
DB $C7, $C9 ; '<=' $C0 + 'no-l-eql'
DB $C8, $CA ; '>=' $C0 + 'no-gr-eql'
DB $C9, $CB ; '<>' $C0 + 'nos-neql'
DB $C5, $C7 ; 'OR' $C0 + 'or'
DB $C6, $C8 ; 'AND' $C0 + 'no-&-no'
DB $00 ; zero end-marker.
; -------------------
; Table of priorities
; -------------------
; This table is indexed with the operation code obtained from the above
; table $C3 - $CF to obtain the priority for the respective operation.
;; tbl-priors
L27B0: DB $06 ; '-' opcode $C3
DB $08 ; '*' opcode $C4
DB $08 ; '/' opcode $C5
DB $0A ; '^' opcode $C6
DB $02 ; 'OR' opcode $C7
DB $03 ; 'AND' opcode $C8
DB $05 ; '<=' opcode $C9
DB $05 ; '>=' opcode $CA
DB $05 ; '<>' opcode $CB
DB $05 ; '>' opcode $CC
DB $05 ; '<' opcode $CD
DB $05 ; '=' opcode $CE
DB $06 ; '+' opcode $CF
; ----------------------
; Scanning function (FN)
; ----------------------
; This routine deals with user-defined functions.
; The definition can be anywhere in the program area but these are best
; placed near the start of the program as we shall see.
; The evaluation process is quite complex as the Spectrum has to parse two
; statements at the same time. Syntax of both has been checked previously
; and hidden locations have been created immediately after each argument
; of the DEF FN statement. Each of the arguments of the FN function is
; evaluated by SCANNING and placed in the hidden locations. Then the
; expression to the right of the DEF FN '=' is evaluated by SCANNING and for
; any variables encountered, a search is made in the DEF FN variable list
; in the program area before searching in the normal variables area.
;
; Recursion is not allowed: i.e. the definition of a function should not use
; the same function, either directly or indirectly ( through another function).
; You'll normally get error 4, ('Out of memory'), although sometimes the sytem
; will crash. - Vickers, Pitman 1984.
;
; As the definition is just an expression, there would seem to be no means
; of breaking out of such recursion.
; However, by the clever use of string expressions and VAL, such recursion is
; possible.
; e.g. DEF FN a(n) = VAL "n+FN a(n-1)+0" ((n<1) * 10 + 1 TO )
; will evaluate the full 11-character expression for all values where n is
; greater than zero but just the 11th character, "0", when n drops to zero
; thereby ending the recursion producing the correct result.
; Recursive string functions are possible using VAL$ instead of VAL and the
; null string as the final addend.
; - from a turn of the century newsgroup discussion initiated by Mike Wynne.
;; S-FN-SBRN
L27BD: CALL L2530 ; routine SYNTAX-Z
JR NZ,L27F7 ; forward to SF-RUN in runtime
RST 20H ; NEXT-CHAR
CALL L2C8D ; routine ALPHA check for letters A-Z a-z
JP NC,L1C8A ; jump back to REPORT-C if not
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR
CP $24 ; is it '$' ?
PUSH AF ; save character and flags
JR NZ,L27D0 ; forward to SF-BRKT-1 with numeric function
RST 20H ; NEXT-CHAR
;; SF-BRKT-1
L27D0: CP $28 ; is '(' ?
JR NZ,L27E6 ; forward to SF-RPRT-C if not
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR
CP $29 ; is it ')' ?
JR Z,L27E9 ; forward to SF-FLAG-6 if no arguments.
;; SF-ARGMTS
L27D9: CALL L24FB ; routine SCANNING checks each argument
; which may be an expression.
RST 18H ; GET-CHAR
CP $2C ; is it a ',' ?
JR NZ,L27E4 ; forward if not to SF-BRKT-2 to test bracket
RST 20H ; NEXT-CHAR if a comma was found
JR L27D9 ; back to SF-ARGMTS to parse all arguments.
; ---
;; SF-BRKT-2
L27E4: CP $29 ; is character the closing ')' ?
;; SF-RPRT-C
L27E6: JP NZ,L1C8A ; jump to REPORT-C
; 'Nonsense in BASIC'
; at this point any optional arguments have had their syntax checked.
;; SF-FLAG-6
L27E9: RST 20H ; NEXT-CHAR
LD HL,$5C3B ; address system variable FLAGS
RES 6,(HL) ; signal string result
POP AF ; restore test against '$'.
JR Z,L27F4 ; forward to SF-SYN-EN if string function.
SET 6,(HL) ; signal numeric result
;; SF-SYN-EN
L27F4: JP L2712 ; jump back to S-CONT-2 to continue scanning.
; ---
; the branch was here in runtime.
;; SF-RUN
L27F7: RST 20H ; NEXT-CHAR fetches name
AND $DF ; AND 11101111 - reset bit 5 - upper-case.
LD B,A ; save in B
RST 20H ; NEXT-CHAR
SUB $24 ; subtract '$'
LD C,A ; save result in C
JR NZ,L2802 ; forward if not '$' to SF-ARGMT1
RST 20H ; NEXT-CHAR advances to bracket
;; SF-ARGMT1
L2802: RST 20H ; NEXT-CHAR advances to start of argument
PUSH HL ; save address
LD HL,($5C53) ; fetch start of program area from PROG
DEC HL ; the search starting point is the previous
; location.
;; SF-FND-DF
L2808: LD DE,$00CE ; search is for token 'DEF FN' in E,
; statement count in D.
PUSH BC ; save C the string test, and B the letter.
CALL L1D86 ; routine LOOK-PROG will search for token.
POP BC ; restore BC.
JR NC,L2814 ; forward to SF-CP-DEF if a match was found.
;; REPORT-P
L2812: RST 08H ; ERROR-1
DB $18 ; Error Report: FN without DEF
;; SF-CP-DEF
L2814: PUSH HL ; save address of DEF FN
CALL L28AB ; routine FN-SKPOVR skips over white-space etc.
; without disturbing CH-ADD.
AND $DF ; make fetched character upper-case.
CP B ; compare with FN name
JR NZ,L2825 ; forward to SF-NOT-FD if no match.
; the letters match so test the type.
CALL L28AB ; routine FN-SKPOVR skips white-space
SUB $24 ; subtract '$' from fetched character
CP C ; compare with saved result of same operation
; on FN name.
JR Z,L2831 ; forward to SF-VALUES with a match.
; the letters matched but one was string and the other numeric.
;; SF-NOT-FD
L2825: POP HL ; restore search point.
DEC HL ; make location before
LD DE,$0200 ; the search is to be for the end of the
; current definition - 2 statements forward.
PUSH BC ; save the letter/type
CALL L198B ; routine EACH-STMT steps past rejected
; definition.
POP BC ; restore letter/type
JR L2808 ; back to SF-FND-DF to continue search
; ---
; Success!
; the branch was here with matching letter and numeric/string type.
;; SF-VALUES
L2831: AND A ; test A ( will be zero if string '$' - '$' )
CALL Z,L28AB ; routine FN-SKPOVR advances HL past '$'.
POP DE ; discard pointer to 'DEF FN'.
POP DE ; restore pointer to first FN argument.
LD ($5C5D),DE ; save in CH_ADD
CALL L28AB ; routine FN-SKPOVR advances HL past '('
PUSH HL ; save start address in DEF FN ***
CP $29 ; is character a ')' ?
JR Z,L2885 ; forward to SF-R-BR-2 if no arguments.
;; SF-ARG-LP
L2843: INC HL ; point to next character.
LD A,(HL) ; fetch it.
CP $0E ; is it the number marker
LD D,$40 ; signal numeric in D.
JR Z,L2852 ; forward to SF-ARG-VL if numeric.
DEC HL ; back to letter
CALL L28AB ; routine FN-SKPOVR skips any white-space
INC HL ; advance past the expected '$' to
; the 'hidden' marker.
LD D,$00 ; signal string.
;; SF-ARG-VL
L2852: INC HL ; now address first of 5-byte location.
PUSH HL ; save address in DEF FN statement
PUSH DE ; save D - result type
CALL L24FB ; routine SCANNING evaluates expression in
; the FN statement setting FLAGS and leaving
; result as last value on calculator stack.
POP AF ; restore saved result type to A
XOR (IY+$01) ; xor with FLAGS
AND $40 ; and with 01000000 to test bit 6
JR NZ,L288B ; forward to REPORT-Q if type mismatch.
; 'Parameter error'
POP HL ; pop the start address in DEF FN statement
EX DE,HL ; transfer to DE ?? pop straight into de ?
LD HL,($5C65) ; set HL to STKEND location after value
LD BC,$0005 ; five bytes to move
SBC HL,BC ; decrease HL by 5 to point to start.
LD ($5C65),HL ; set STKEND 'removing' value from stack.
LDIR ; copy value into DEF FN statement
EX DE,HL ; set HL to location after value in DEF FN
DEC HL ; step back one
CALL L28AB ; routine FN-SKPOVR gets next valid character
CP $29 ; is it ')' end of arguments ?
JR Z,L2885 ; forward to SF-R-BR-2 if so.
; a comma separator has been encountered in the DEF FN argument list.
PUSH HL ; save position in DEF FN statement
RST 18H ; GET-CHAR from FN statement
CP $2C ; is it ',' ?
JR NZ,L288B ; forward to REPORT-Q if not
; 'Parameter error'
RST 20H ; NEXT-CHAR in FN statement advances to next
; argument.
POP HL ; restore DEF FN pointer
CALL L28AB ; routine FN-SKPOVR advances to corresponding
; argument.
JR L2843 ; back to SF-ARG-LP looping until all
; arguments are passed into the DEF FN
; hidden locations.
; ---
; the branch was here when all arguments passed.
;; SF-R-BR-2
L2885: PUSH HL ; save location of ')' in DEF FN
RST 18H ; GET-CHAR gets next character in FN
CP $29 ; is it a ')' also ?
JR Z,L288D ; forward to SF-VALUE if so.
;; REPORT-Q
L288B: RST 08H ; ERROR-1
DB $19 ; Error Report: Parameter error
;; SF-VALUE
L288D: POP DE ; location of ')' in DEF FN to DE.
EX DE,HL ; now to HL, FN ')' pointer to DE.
LD ($5C5D),HL ; initialize CH_ADD to this value.
; At this point the start of the DEF FN argument list is on the machine stack.
; We also have to consider that this defined function may form part of the
; definition of another defined function (though not itself).
; As this defined function may be part of a hierarchy of defined functions
; currently being evaluated by recursive calls to SCANNING, then we have to
; preserve the original value of DEFADD and not assume that it is zero.
LD HL,($5C0B) ; get original DEFADD address
EX (SP),HL ; swap with DEF FN address on stack ***
LD ($5C0B),HL ; set DEFADD to point to this argument list
; during scanning.
PUSH DE ; save FN ')' pointer.
RST 20H ; NEXT-CHAR advances past ')' in define
RST 20H ; NEXT-CHAR advances past '=' to expression
CALL L24FB ; routine SCANNING evaluates but searches
; initially for variables at DEFADD
POP HL ; pop the FN ')' pointer
LD ($5C5D),HL ; set CH_ADD to this
POP HL ; pop the original DEFADD value
LD ($5C0B),HL ; and re-insert into DEFADD system variable.
RST 20H ; NEXT-CHAR advances to character after ')'
JP L2712 ; to S-CONT-2 - to continue current
; invocation of scanning
; --------------------
; Used to parse DEF FN
; --------------------
; e.g. DEF FN s $ ( x ) = b $ ( TO x ) : REM exaggerated
;
; This routine is used 10 times to advance along a DEF FN statement
; skipping spaces and colour control codes. It is similar to NEXT-CHAR
; which is, at the same time, used to skip along the corresponding FN function
; except the latter has to deal with AT and TAB characters in string
; expressions. These cannot occur in a program area so this routine is
; simpler as both colour controls and their parameters are less than space.
;; FN-SKPOVR
L28AB: INC HL ; increase pointer
LD A,(HL) ; fetch addressed character
CP $21 ; compare with space + 1
JR C,L28AB ; back to FN-SKPOVR if less
RET ; return pointing to a valid character.
; ---------
; LOOK-VARS
; ---------
;
;
;; LOOK-VARS
L28B2: SET 6,(IY+$01) ; update FLAGS - presume numeric result
RST 18H ; GET-CHAR
CALL L2C8D ; routine ALPHA tests for A-Za-z
JP NC,L1C8A ; jump to REPORT-C if not.
; 'Nonsense in BASIC'
PUSH HL ; save pointer to first letter ^1
AND $1F ; mask lower bits, 1 - 26 decimal 000xxxxx
LD C,A ; store in C.
RST 20H ; NEXT-CHAR
PUSH HL ; save pointer to second character ^2
CP $28 ; is it '(' - an array ?
JR Z,L28EF ; forward to V-RUN/SYN if so.
SET 6,C ; set 6 signaling string if solitary 010
CP $24 ; is character a '$' ?
JR Z,L28DE ; forward to V-STR-VAR
SET 5,C ; signal numeric 011
CALL L2C88 ; routine ALPHANUM sets carry if second
; character is alphanumeric.
JR NC,L28E3 ; forward to V-TEST-FN if just one character
; it is more than one character but re-test current character so that 6 reset
; Note. this is a rare lack of elegance. Bit 6 could be reset once before
; entering the loop. Another puzzle is that this loop renders the similar
; loop at V-PASS redundant.
;; V-CHAR
L28D4: CALL L2C88 ; routine ALPHANUM
JR NC,L28EF ; to V-RUN/SYN when no more
RES 6,C ; make long named type 001
RST 20H ; NEXT-CHAR
JR L28D4 ; loop back to V-CHAR
; ---
;; V-STR-VAR
L28DE: RST 20H ; NEXT-CHAR advances past '$'
RES 6,(IY+$01) ; update FLAGS - signal string result.
;; V-TEST-FN
L28E3: LD A,($5C0C) ; load A with DEFADD_hi
AND A ; and test for zero.
JR Z,L28EF ; forward to V-RUN/SYN if a defined function
; is not being evaluated.
; Note.
CALL L2530 ; routine SYNTAX-Z
JP NZ,L2951 ; JUMP to STK-F-ARG in runtime and then
; back to this point if no variable found.
;; V-RUN/SYN
L28EF: LD B,C ; save flags in B
CALL L2530 ; routine SYNTAX-Z
JR NZ,L28FD ; to V-RUN to look for the variable in runtime
; if checking syntax the letter is not returned
LD A,C ; copy letter/flags to A
AND $E0 ; and with 11100000 to get rid of the letter
SET 7,A ; use spare bit to signal checking syntax.
LD C,A ; and transfer to C.
JR L2934 ; forward to V-SYNTAX
; ---
; but in runtime search for the variable.
;; V-RUN
L28FD: LD HL,($5C4B) ; set HL to start of variables from VARS
;; V-EACH
L2900: LD A,(HL) ; get first character
AND $7F ; and with 01111111
; ignoring bit 7 which distinguishes
; arrays or for/next variables.
JR Z,L2932 ; to V-80-BYTE if zero as must be 10000000
; the variables end-marker.
CP C ; compare with supplied value.
JR NZ,L292A ; forward to V-NEXT if no match.
RLA ; destructively test
ADD A,A ; bits 5 and 6 of A
; jumping if bit 5 reset or 6 set
JP P,L293F ; to V-FOUND-2 strings and arrays
JR C,L293F ; to V-FOUND-2 simple and for next
; leaving long name variables.
POP DE ; pop pointer to 2nd. char
PUSH DE ; save it again
PUSH HL ; save variable first character pointer
;; V-MATCHES
L2912: INC HL ; address next character in vars area
;; V-SPACES
L2913: LD A,(DE) ; pick up letter from prog area
INC DE ; and advance address
CP $20 ; is it a space
JR Z,L2913 ; back to V-SPACES until non-space
OR $20 ; convert to range 1 - 26.
CP (HL) ; compare with addressed variables character
JR Z,L2912 ; loop back to V-MATCHES if a match on an
; intermediate letter.
OR $80 ; now set bit 7 as last character of long
; names are inverted.
CP (HL) ; compare again
JR NZ,L2929 ; forward to V-GET-PTR if no match
; but if they match check that this is also last letter in prog area
LD A,(DE) ; fetch next character
CALL L2C88 ; routine ALPHANUM sets carry if not alphanum
JR NC,L293E ; forward to V-FOUND-1 with a full match.
;; V-GET-PTR
L2929: POP HL ; pop saved pointer to char 1
;; V-NEXT
L292A: PUSH BC ; save flags
CALL L19B8 ; routine NEXT-ONE gets next variable in DE
EX DE,HL ; transfer to HL.
POP BC ; restore the flags
JR L2900 ; loop back to V-EACH
; to compare each variable
; ---
;; V-80-BYTE
L2932: SET 7,B ; will signal not found
; the branch was here when checking syntax
;; V-SYNTAX
L2934: POP DE ; discard the pointer to 2nd. character v2
; in BASIC line/workspace.
RST 18H ; GET-CHAR gets character after variable name.
CP $28 ; is it '(' ?
JR Z,L2943 ; forward to V-PASS
; Note. could go straight to V-END ?
SET 5,B ; signal not an array
JR L294B ; forward to V-END
; ---------------------------
; the jump was here when a long name matched and HL pointing to last character
; in variables area.
;; V-FOUND-1
L293E: POP DE ; discard pointer to first var letter
; the jump was here with all other matches HL points to first var char.
;; V-FOUND-2
L293F: POP DE ; discard pointer to 2nd prog char v2
POP DE ; drop pointer to 1st prog char v1
PUSH HL ; save pointer to last char in vars
RST 18H ; GET-CHAR
;; V-PASS
L2943: CALL L2C88 ; routine ALPHANUM
JR NC,L294B ; forward to V-END if not
; but it never will be as we advanced past long-named variables earlier.
RST 20H ; NEXT-CHAR
JR L2943 ; back to V-PASS
; ---
;; V-END
L294B: POP HL ; pop the pointer to first character in
; BASIC line/workspace.
RL B ; rotate the B register left
; bit 7 to carry
BIT 6,B ; test the array indicator bit.
RET ; return
; -----------------------
; Stack function argument
; -----------------------
; This branch is taken from LOOK-VARS when a defined function is currently
; being evaluated.
; Scanning is evaluating the expression after the '=' and the variable
; found could be in the argument list to the left of the '=' or in the
; normal place after the program. Preference will be given to the former.
; The variable name to be matched is in C.
;; STK-F-ARG
L2951: LD HL,($5C0B) ; set HL to DEFADD
LD A,(HL) ; load the first character
CP $29 ; is it ')' ?
JP Z,L28EF ; JUMP back to V-RUN/SYN, if so, as there are
; no arguments.
; but proceed to search argument list of defined function first if not empty.
;; SFA-LOOP
L295A: LD A,(HL) ; fetch character again.
OR $60 ; or with 01100000 presume a simple variable.
LD B,A ; save result in B.
INC HL ; address next location.
LD A,(HL) ; pick up byte.
CP $0E ; is it the number marker ?
JR Z,L296B ; forward to SFA-CP-VR if so.
; it was a string. White-space may be present but syntax has been checked.
DEC HL ; point back to letter.
CALL L28AB ; routine FN-SKPOVR skips to the '$'
INC HL ; now address the hidden marker.
RES 5,B ; signal a string variable.
;; SFA-CP-VR
L296B: LD A,B ; transfer found variable letter to A.
CP C ; compare with expected.
JR Z,L2981 ; forward to SFA-MATCH with a match.
INC HL ; step
INC HL ; past
INC HL ; the
INC HL ; five
INC HL ; bytes.
CALL L28AB ; routine FN-SKPOVR skips to next character
CP $29 ; is it ')' ?
JP Z,L28EF ; jump back if so to V-RUN/SYN to look in
; normal variables area.
CALL L28AB ; routine FN-SKPOVR skips past the ','
; all syntax has been checked and these
; things can be taken as read.
JR L295A ; back to SFA-LOOP while there are more
; arguments.
; ---
;; SFA-MATCH
L2981: BIT 5,C ; test if numeric
JR NZ,L2991 ; to SFA-END if so as will be stacked
; by scanning
INC HL ; point to start of string descriptor
LD DE,($5C65) ; set DE to STKEND
CALL L33C0 ; routine MOVE-FP puts parameters on stack.
EX DE,HL ; new free location to HL.
LD ($5C65),HL ; use it to set STKEND system variable.
;; SFA-END
L2991: POP DE ; discard
POP DE ; pointers.
XOR A ; clear carry flag.
INC A ; and zero flag.
RET ; return.
; ------------------------
; Stack variable component
; ------------------------
; This is called to evaluate a complex structure that has been found, in
; runtime, by LOOK-VARS in the variables area.
; In this case HL points to the initial letter, bits 7-5
; of which indicate the type of variable.
; 010 - simple string, 110 - string array, 100 - array of numbers.
;
; It is called from CLASS-01 when assigning to a string or array including
; a slice.
; It is called from SCANNING to isolate the required part of the structure.
;
; An important part of the runtime process is to check that the number of
; dimensions of the variable match the number of subscripts supplied in the
; BASIC line.
;
; If checking syntax,
; the B register, which counts dimensions is set to zero (256) to allow
; the loop to continue till all subscripts are checked. While doing this it
; is reading dimension sizes from some arbitrary area of memory. Although
; these are meaningless it is of no concern as the limit is never checked by
; int-exp during syntax checking.
;
; The routine is also called from the syntax path of DIM command to check the
; syntax of both string and numeric arrays definitions except that bit 6 of C
; is reset so both are checked as numeric arrays. This ruse avoids a terminal
; slice being accepted as part of the DIM command.
; All that is being checked is that there are a valid set of comma-separated
; expressions before a terminal ')', although, as above, it will still go
; through the motions of checking dummy dimension sizes.
;; STK-VAR
L2996: XOR A ; clear A
LD B,A ; and B, the syntax dimension counter (256)
BIT 7,C ; checking syntax ?
JR NZ,L29E7 ; forward to SV-COUNT if so.
; runtime evaluation.
BIT 7,(HL) ; will be reset if a simple string.
JR NZ,L29AE ; forward to SV-ARRAYS otherwise
INC A ; set A to 1, simple string.
;; SV-SIMPLE$
L29A1: INC HL ; address length low
LD C,(HL) ; place in C
INC HL ; address length high
LD B,(HL) ; place in B
INC HL ; address start of string
EX DE,HL ; DE = start now.
CALL L2AB2 ; routine STK-STO-$ stacks string parameters
; DE start in variables area,
; BC length, A=1 simple string
; the only thing now is to consider if a slice is required.
RST 18H ; GET-CHAR puts character at CH_ADD in A
JP L2A49 ; jump forward to SV-SLICE? to test for '('
; --------------------------------------------------------
; the branch was here with string and numeric arrays in runtime.
;; SV-ARRAYS
L29AE: INC HL ; step past
INC HL ; the total length
INC HL ; to address Number of dimensions.
LD B,(HL) ; transfer to B overwriting zero.
BIT 6,C ; a numeric array ?
JR Z,L29C0 ; forward to SV-PTR with numeric arrays
DEC B ; ignore the final element of a string array
; the fixed string size.
JR Z,L29A1 ; back to SV-SIMPLE$ if result is zero as has
; been created with DIM a$(10) for instance
; and can be treated as a simple string.
; proceed with multi-dimensioned string arrays in runtime.
EX DE,HL ; save pointer to dimensions in DE
RST 18H ; GET-CHAR looks at the BASIC line
CP $28 ; is character '(' ?
JR NZ,L2A20 ; to REPORT-3 if not
; 'Subscript wrong'
EX DE,HL ; dimensions pointer to HL to synchronize
; with next instruction.
; runtime numeric arrays path rejoins here.
;; SV-PTR
L29C0: EX DE,HL ; save dimension pointer in DE
JR L29E7 ; forward to SV-COUNT with true no of dims
; in B. As there is no initial comma the
; loop is entered at the midpoint.
; ----------------------------------------------------------
; the dimension counting loop which is entered at mid-point.
;; SV-COMMA
L29C3: PUSH HL ; save counter
RST 18H ; GET-CHAR
POP HL ; pop counter
CP $2C ; is character ',' ?
JR Z,L29EA ; forward to SV-LOOP if so
; in runtime the variable definition indicates a comma should appear here
BIT 7,C ; checking syntax ?
JR Z,L2A20 ; forward to REPORT-3 if not
; 'Subscript error'
; proceed if checking syntax of an array?
BIT 6,C ; array of strings
JR NZ,L29D8 ; forward to SV-CLOSE if so
; an array of numbers.
CP $29 ; is character ')' ?
JR NZ,L2A12 ; forward to SV-RPT-C if not
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR moves CH-ADD past the statement
RET ; return ->
; ---
; the branch was here with an array of strings.
;; SV-CLOSE
L29D8: CP $29 ; as above ')' could follow the expression
JR Z,L2A48 ; forward to SV-DIM if so
CP $CC ; is it 'TO' ?
JR NZ,L2A12 ; to SV-RPT-C with anything else
; 'Nonsense in BASIC'
; now backtrack CH_ADD to set up for slicing routine.
; Note. in a BASIC line we can safely backtrack to a colour parameter.
;; SV-CH-ADD
L29E0: RST 18H ; GET-CHAR
DEC HL ; backtrack HL
LD ($5C5D),HL ; to set CH_ADD up for slicing routine
JR L2A45 ; forward to SV-SLICE and make a return
; when all slicing complete.
; ----------------------------------------
; -> the mid-point entry point of the loop
;; SV-COUNT
L29E7: LD HL,$0000 ; initialize data pointer to zero.
;; SV-LOOP
L29EA: PUSH HL ; save the data pointer.
RST 20H ; NEXT-CHAR in BASIC area points to an
; expression.
POP HL ; restore the data pointer.
LD A,C ; transfer name/type to A.
CP $C0 ; is it 11000000 ?
; Note. the letter component is absent if
; syntax checking.
JR NZ,L29FB ; forward to SV-MULT if not an array of
; strings.
; proceed to check string arrays during syntax.
RST 18H ; GET-CHAR
CP $29 ; ')' end of subscripts ?
JR Z,L2A48 ; forward to SV-DIM to consider further slice
CP $CC ; is it 'TO' ?
JR Z,L29E0 ; back to SV-CH-ADD to consider a slice.
; (no need to repeat get-char at L29E0)
; if neither, then an expression is required so rejoin runtime loop ??
; registers HL and DE only point to somewhere meaningful in runtime so
; comments apply to that situation.
;; SV-MULT
L29FB: PUSH BC ; save dimension number.
PUSH HL ; push data pointer/rubbish.
; DE points to current dimension.
CALL L2AEE ; routine DE,(DE+1) gets next dimension in DE
; and HL points to it.
EX (SP),HL ; dim pointer to stack, data pointer to HL (*)
EX DE,HL ; data pointer to DE, dim size to HL.
CALL L2ACC ; routine INT-EXP1 checks integer expression
; and gets result in BC in runtime.
JR C,L2A20 ; to REPORT-3 if > HL
; 'Subscript out of range'
DEC BC ; adjust returned result from 1-x to 0-x
CALL L2AF4 ; routine GET-HL*DE multiplies data pointer by
; dimension size.
ADD HL,BC ; add the integer returned by expression.
POP DE ; pop the dimension pointer. ***
POP BC ; pop dimension counter.
DJNZ L29C3 ; back to SV-COMMA if more dimensions
; Note. during syntax checking, unless there
; are more than 256 subscripts, the branch
; back to SV-COMMA is always taken.
BIT 7,C ; are we checking syntax ?
; then we've got a joker here.
;; SV-RPT-C
L2A12: JR NZ,L2A7A ; forward to SL-RPT-C if so
; 'Nonsense in BASIC'
; more than 256 subscripts in BASIC line.
; but in runtime the number of subscripts are at least the same as dims
PUSH HL ; save data pointer.
BIT 6,C ; is it a string array ?
JR NZ,L2A2C ; forward to SV-ELEM$ if so.
; a runtime numeric array subscript.
LD B,D ; register DE has advanced past all dimensions
LD C,E ; and points to start of data in variable.
; transfer it to BC.
RST 18H ; GET-CHAR checks BASIC line
CP $29 ; must be a ')' ?
JR Z,L2A22 ; skip to SV-NUMBER if so
; else more subscripts in BASIC line than the variable definition.
;; REPORT-3
L2A20: RST 08H ; ERROR-1
DB $02 ; Error Report: Subscript wrong
; continue if subscripts matched the numeric array.
;; SV-NUMBER
L2A22: RST 20H ; NEXT-CHAR moves CH_ADD to next statement
; - finished parsing.
POP HL ; pop the data pointer.
LD DE,$0005 ; each numeric element is 5 bytes.
CALL L2AF4 ; routine GET-HL*DE multiplies.
ADD HL,BC ; now add to start of data in the variable.
RET ; return with HL pointing at the numeric
; array subscript. ->
; ---------------------------------------------------------------
; the branch was here for string subscripts when the number of subscripts
; in the BASIC line was one less than in variable definition.
;; SV-ELEM$
L2A2C: CALL L2AEE ; routine DE,(DE+1) gets final dimension
; the length of strings in this array.
EX (SP),HL ; start pointer to stack, data pointer to HL.
CALL L2AF4 ; routine GET-HL*DE multiplies by element
; size.
POP BC ; the start of data pointer is added
ADD HL,BC ; in - now points to location before.
INC HL ; point to start of required string.
LD B,D ; transfer the length (final dimension size)
LD C,E ; from DE to BC.
EX DE,HL ; put start in DE.
CALL L2AB1 ; routine STK-ST-0 stores the string parameters
; with A=0 - a slice or subscript.
; now check that there were no more subscripts in the BASIC line.
RST 18H ; GET-CHAR
CP $29 ; is it ')' ?
JR Z,L2A48 ; forward to SV-DIM to consider a separate
; subscript or/and a slice.
CP $2C ; a comma is allowed if the final subscript
; is to be sliced e.g a$(2,3,4 TO 6).
JR NZ,L2A20 ; to REPORT-3 with anything else
; 'Subscript error'
;; SV-SLICE
L2A45: CALL L2A52 ; routine SLICING slices the string.
; but a slice of a simple string can itself be sliced.
;; SV-DIM
L2A48: RST 20H ; NEXT-CHAR
;; SV-SLICE?
L2A49: CP $28 ; is character '(' ?
JR Z,L2A45 ; loop back if so to SV-SLICE
RES 6,(IY+$01) ; update FLAGS - Signal string result
RET ; and return.
; ---
; The above section deals with the flexible syntax allowed.
; DIM a$(3,3,10) can be considered as two dimensional array of ten-character
; strings or a 3-dimensional array of characters.
; a$(1,1) will return a 10-character string as will a$(1,1,1 TO 10)
; a$(1,1,1) will return a single character.
; a$(1,1) (1 TO 6) is the same as a$(1,1,1 TO 6)
; A slice can itself be sliced ad infinitum
; b$ () () () () () () (2 TO 10) (2 TO 9) (3) is the same as b$(5)
; -------------------------
; Handle slicing of strings
; -------------------------
; The syntax of string slicing is very natural and it is as well to reflect
; on the permutations possible.
; a$() and a$( TO ) indicate the entire string although just a$ would do
; and would avoid coming here.
; h$(16) indicates the single character at position 16.
; a$( TO 32) indicates the first 32 characters.
; a$(257 TO) indicates all except the first 256 characters.
; a$(19000 TO 19999) indicates the thousand characters at position 19000.
; Also a$(9 TO 5) returns a null string not an error.
; This enables a$(2 TO) to return a null string if the passed string is
; of length zero or 1.
; A string expression in brackets can be sliced. e.g. (STR$ PI) (3 TO )
; We arrived here from SCANNING with CH-ADD pointing to the initial '('
; or from above.
;; SLICING
L2A52: CALL L2530 ; routine SYNTAX-Z
CALL NZ,L2BF1 ; routine STK-FETCH fetches parameters of
; string at runtime, start in DE, length
; in BC. This could be an array subscript.
RST 20H ; NEXT-CHAR
CP $29 ; is it ')' ? e.g. a$()
JR Z,L2AAD ; forward to SL-STORE to store entire string.
PUSH DE ; else save start address of string
XOR A ; clear accumulator to use as a running flag.
PUSH AF ; and save on stack before any branching.
PUSH BC ; save length of string to be sliced.
LD DE,$0001 ; default the start point to position 1.
RST 18H ; GET-CHAR
POP HL ; pop length to HL as default end point
; and limit.
CP $CC ; is it 'TO' ? e.g. a$( TO 10000)
JR Z,L2A81 ; to SL-SECOND to evaluate second parameter.
POP AF ; pop the running flag.
CALL L2ACD ; routine INT-EXP2 fetches first parameter.
PUSH AF ; save flag (will be $FF if parameter>limit)
LD D,B ; transfer the start
LD E,C ; to DE overwriting 0001.
PUSH HL ; save original length.
RST 18H ; GET-CHAR
POP HL ; pop the limit length.
CP $CC ; is it 'TO' after a start ?
JR Z,L2A81 ; to SL-SECOND to evaluate second parameter
CP $29 ; is it ')' ? e.g. a$(365)
;; SL-RPT-C
L2A7A: JP NZ,L1C8A ; jump to REPORT-C with anything else
; 'Nonsense in BASIC'
LD H,D ; copy start
LD L,E ; to end - just a one character slice.
JR L2A94 ; forward to SL-DEFINE.
; ---------------------
;; SL-SECOND
L2A81: PUSH HL ; save limit length.
RST 20H ; NEXT-CHAR
POP HL ; pop the length.
CP $29 ; is character ')' ? e.g a$(7 TO )
JR Z,L2A94 ; to SL-DEFINE using length as end point.
POP AF ; else restore flag.
CALL L2ACD ; routine INT-EXP2 gets second expression.
PUSH AF ; save the running flag.
RST 18H ; GET-CHAR
LD H,B ; transfer second parameter
LD L,C ; to HL. e.g. a$(42 to 99)
CP $29 ; is character a ')' ?
JR NZ,L2A7A ; to SL-RPT-C if not
; 'Nonsense in BASIC'
; we now have start in DE and an end in HL.
;; SL-DEFINE
L2A94: POP AF ; pop the running flag.
EX (SP),HL ; put end point on stack, start address to HL
ADD HL,DE ; add address of string to the start point.
DEC HL ; point to first character of slice.
EX (SP),HL ; start address to stack, end point to HL (*)
AND A ; prepare to subtract.
SBC HL,DE ; subtract start point from end point.
LD BC,$0000 ; default the length result to zero.
JR C,L2AA8 ; forward to SL-OVER if start > end.
INC HL ; increment the length for inclusive byte.
AND A ; now test the running flag.
JP M,L2A20 ; jump back to REPORT-3 if $FF.
; 'Subscript out of range'
LD B,H ; transfer the length
LD C,L ; to BC.
;; SL-OVER
L2AA8: POP DE ; restore start address from machine stack ***
RES 6,(IY+$01) ; update FLAGS - signal string result for
; syntax.
;; SL-STORE
L2AAD: CALL L2530 ; routine SYNTAX-Z (UNSTACK-Z?)
RET Z ; return if checking syntax.
; but continue to store the string in runtime.
; ------------------------------------
; other than from above, this routine is called from STK-VAR to stack
; a known string array element.
; ------------------------------------
;; STK-ST-0
L2AB1: XOR A ; clear to signal a sliced string or element.
; -------------------------
; this routine is called from chr$, scrn$ etc. to store a simple string result.
; --------------------------
;; STK-STO-$
L2AB2: RES 6,(IY+$01) ; update FLAGS - signal string result.
; and continue to store parameters of string.
; ---------------------------------------
; Pass five registers to calculator stack
; ---------------------------------------
; This subroutine puts five registers on the calculator stack.
;; STK-STORE
L2AB6: PUSH BC ; save two registers
CALL L33A9 ; routine TEST-5-SP checks room and puts 5
; in BC.
POP BC ; fetch the saved registers.
LD HL,($5C65) ; make HL point to first empty location STKEND
LD (HL),A ; place the 5 registers.
INC HL ;
LD (HL),E ;
INC HL ;
LD (HL),D ;
INC HL ;
LD (HL),C ;
INC HL ;
LD (HL),B ;
INC HL ;
LD ($5C65),HL ; update system variable STKEND.
RET ; and return.
; -------------------------------------------
; Return result of evaluating next expression
; -------------------------------------------
; This clever routine is used to check and evaluate an integer expression
; which is returned in BC, setting A to $FF, if greater than a limit supplied
; in HL. It is used to check array subscripts, parameters of a string slice
; and the arguments of the DIM command. In the latter case, the limit check
; is not required and H is set to $FF. When checking optional string slice
; parameters, it is entered at the second entry point so as not to disturb
; the running flag A, which may be $00 or $FF from a previous invocation.
;; INT-EXP1
L2ACC: XOR A ; set result flag to zero.
; -> The entry point is here if A is used as a running flag.
;; INT-EXP2
L2ACD: PUSH DE ; preserve DE register throughout.
PUSH HL ; save the supplied limit.
PUSH AF ; save the flag.
CALL L1C82 ; routine EXPT-1NUM evaluates expression
; at CH_ADD returning if numeric result,
; with value on calculator stack.
POP AF ; pop the flag.
CALL L2530 ; routine SYNTAX-Z
JR Z,L2AEB ; forward to I-RESTORE if checking syntax so
; avoiding a comparison with supplied limit.
PUSH AF ; save the flag.
CALL L1E99 ; routine FIND-INT2 fetches value from
; calculator stack to BC producing an error
; if too high.
POP DE ; pop the flag to D.
LD A,B ; test value for zero and reject
OR C ; as arrays and strings begin at 1.
SCF ; set carry flag.
JR Z,L2AE8 ; forward to I-CARRY if zero.
POP HL ; restore the limit.
PUSH HL ; and save.
AND A ; prepare to subtract.
SBC HL,BC ; subtract value from limit.
;; I-CARRY
L2AE8: LD A,D ; move flag to accumulator $00 or $FF.
SBC A,$00 ; will set to $FF if carry set.
;; I-RESTORE
L2AEB: POP HL ; restore the limit.
POP DE ; and DE register.
RET ; return.
; -----------------------
; LD DE,(DE+1) Subroutine
; -----------------------
; This routine just loads the DE register with the contents of the two
; locations following the location addressed by DE.
; It is used to step along the 16-bit dimension sizes in array definitions.
; Note. Such code is made into subroutines to make programs easier to
; write and it would use less space to include the five instructions in-line.
; However, there are so many exchanges going on at the places this is invoked
; that to implement it in-line would make the code hard to follow.
; It probably had a zippier label though as the intention is to simplify the
; program.
;; DE,(DE+1)
L2AEE: EX DE,HL ;
INC HL ;
LD E,(HL) ;
INC HL ;
LD D,(HL) ;
RET ;
; -------------------
; HL=HL*DE Subroutine
; -------------------
; This routine calls the mathematical routine to multiply HL by DE in runtime.
; It is called from STK-VAR and from DIM. In the latter case syntax is not
; being checked so the entry point could have been at the second CALL
; instruction to save a few clock-cycles.
;; GET-HL*DE
L2AF4: CALL L2530 ; routine SYNTAX-Z.
RET Z ; return if checking syntax.
CALL L30A9 ; routine HL-HL*DE.
JP C,L1F15 ; jump back to REPORT-4 if over 65535.
RET ; else return with 16-bit result in HL.
; -----------------
; THE 'LET' COMMAND
; -----------------
; Sinclair BASIC adheres to the ANSI-78 standard and a LET is required in
; assignments e.g. LET a = 1 : LET h$ = "hat".
;
; Long names may contain spaces but not colour controls (when assigned).
; a substring can appear to the left of the equals sign.
; An earlier mathematician Lewis Carroll may have been pleased that
; 10 LET Babies cannot manage crocodiles = Babies are illogical AND
; Nobody is despised who can manage a crocodile AND Illogical persons
; are despised
; does not give the 'Nonsense..' error if the three variables exist.
; I digress.
;; LET
L2AFF: LD HL,($5C4D) ; fetch system variable DEST to HL.
BIT 1,(IY+$37) ; test FLAGX - handling a new variable ?
JR Z,L2B66 ; forward to L-EXISTS if not.
; continue for a new variable. DEST points to start in BASIC line.
; from the CLASS routines.
LD BC,$0005 ; assume numeric and assign an initial 5 bytes
;; L-EACH-CH
L2B0B: INC BC ; increase byte count for each relevant
; character
;; L-NO-SP
L2B0C: INC HL ; increase pointer.
LD A,(HL) ; fetch character.
CP $20 ; is it a space ?
JR Z,L2B0C ; back to L-NO-SP is so.
JR NC,L2B1F ; forward to L-TEST-CH if higher.
CP $10 ; is it $00 - $0F ?
JR C,L2B29 ; forward to L-SPACES if so.
CP $16 ; is it $16 - $1F ?
JR NC,L2B29 ; forward to L-SPACES if so.
; it was $10 - $15 so step over a colour code.
INC HL ; increase pointer.
JR L2B0C ; loop back to L-NO-SP.
; ---
; the branch was to here if higher than space.
;; L-TEST-CH
L2B1F: CALL L2C88 ; routine ALPHANUM sets carry if alphanumeric
JR C,L2B0B ; loop back to L-EACH-CH for more if so.
CP $24 ; is it '$' ?
JP Z,L2BC0 ; jump forward if so, to L-NEW$
; with a new string.
;; L-SPACES
L2B29: LD A,C ; save length lo in A.
LD HL,($5C59) ; fetch E_LINE to HL.
DEC HL ; point to location before, the variables
; end-marker.
CALL L1655 ; routine MAKE-ROOM creates BC spaces
; for name and numeric value.
INC HL ; advance to first new location.
INC HL ; then to second.
EX DE,HL ; set DE to second location.
PUSH DE ; save this pointer.
LD HL,($5C4D) ; reload HL with DEST.
DEC DE ; point to first.
SUB $06 ; subtract six from length_lo.
LD B,A ; save count in B.
JR Z,L2B4F ; forward to L-SINGLE if it was just
; one character.
; HL points to start of variable name after 'LET' in BASIC line.
;; L-CHAR
L2B3E: INC HL ; increase pointer.
LD A,(HL) ; pick up character.
CP $21 ; is it space or higher ?
JR C,L2B3E ; back to L-CHAR with space and less.
OR $20 ; make variable lower-case.
INC DE ; increase destination pointer.
LD (DE),A ; and load to edit line.
DJNZ L2B3E ; loop back to L-CHAR until B is zero.
OR $80 ; invert the last character.
LD (DE),A ; and overwrite that in edit line.
; now consider first character which has bit 6 set
LD A,$C0 ; set A 11000000 is xor mask for a long name.
; %101 is xor/or result
; single character numerics rejoin here with %00000000 in mask.
; %011 will be xor/or result
;; L-SINGLE
L2B4F: LD HL,($5C4D) ; fetch DEST - HL addresses first character.
XOR (HL) ; apply variable type indicator mask (above).
OR $20 ; make lowercase - set bit 5.
POP HL ; restore pointer to 2nd character.
CALL L2BEA ; routine L-FIRST puts A in first character.
; and returns with HL holding
; new E_LINE-1 the $80 vars end-marker.
;; L-NUMERIC
L2B59: PUSH HL ; save the pointer.
; the value of variable is deleted but remains after calculator stack.
RST 28H ;; FP-CALC
DB $02 ;;delete ; delete variable value
DB $38 ;;end-calc
; DE (STKEND) points to start of value.
POP HL ; restore the pointer.
LD BC,$0005 ; start of number is five bytes before.
AND A ; prepare for true subtraction.
SBC HL,BC ; HL points to start of value.
JR L2BA6 ; forward to L-ENTER ==>
; ---
; the jump was to here if the variable already existed.
;; L-EXISTS
L2B66: BIT 6,(IY+$01) ; test FLAGS - numeric or string result ?
JR Z,L2B72 ; skip forward to L-DELETE$ -*->
; if string result.
; A numeric variable could be simple or an array element.
; They are treated the same and the old value is overwritten.
LD DE,$0006 ; six bytes forward points to loc past value.
ADD HL,DE ; add to start of number.
JR L2B59 ; back to L-NUMERIC to overwrite value.
; ---
; -*-> the branch was here if a string existed.
;; L-DELETE$
L2B72: LD HL,($5C4D) ; fetch DEST to HL.
; (still set from first instruction)
LD BC,($5C72) ; fetch STRLEN to BC.
BIT 0,(IY+$37) ; test FLAGX - handling a complete simple
; string ?
JR NZ,L2BAF ; forward to L-ADD$ if so.
; must be a string array or a slice in workspace.
; Note. LET a$(3 TO 6) = h$ will assign "hat " if h$ = "hat"
; and "hats" if h$ = "hatstand".
;
; This is known as Procrustian lengthening and shortening after a
; character Procrustes in Greek legend who made travellers sleep in his bed,
; cutting off their feet or stretching them so they fitted the bed perfectly.
; The bloke was hatstand and slain by Theseus.
LD A,B ; test if length
OR C ; is zero and
RET Z ; return if so.
PUSH HL ; save pointer to start.
RST 30H ; BC-SPACES creates room.
PUSH DE ; save pointer to first new location.
PUSH BC ; and length (*)
LD D,H ; set DE to point to last location.
LD E,L ;
INC HL ; set HL to next location.
LD (HL),$20 ; place a space there.
LDDR ; copy bytes filling with spaces.
PUSH HL ; save pointer to start.
CALL L2BF1 ; routine STK-FETCH start to DE,
; length to BC.
POP HL ; restore the pointer.
EX (SP),HL ; (*) length to HL, pointer to stack.
AND A ; prepare for true subtraction.
SBC HL,BC ; subtract old length from new.
ADD HL,BC ; and add back.
JR NC,L2B9B ; forward if it fits to L-LENGTH.
LD B,H ; otherwise set
LD C,L ; length to old length.
; "hatstand" becomes "hats"
;; L-LENGTH
L2B9B: EX (SP),HL ; (*) length to stack, pointer to HL.
EX DE,HL ; pointer to DE, start of string to HL.
LD A,B ; is the length zero ?
OR C ;
JR Z,L2BA3 ; forward to L-IN-W/S if so
; leaving prepared spaces.
LDIR ; else copy bytes overwriting some spaces.
;; L-IN-W/S
L2BA3: POP BC ; pop the new length. (*)
POP DE ; pop pointer to new area.
POP HL ; pop pointer to variable in assignment.
; and continue copying from workspace
; to variables area.
; ==> branch here from L-NUMERIC
;; L-ENTER
L2BA6: EX DE,HL ; exchange pointers HL=STKEND DE=end of vars.
LD A,B ; test the length
OR C ; and make a
RET Z ; return if zero (strings only).
PUSH DE ; save start of destination.
LDIR ; copy bytes.
POP HL ; address the start.
RET ; and return.
; ---
; the branch was here from L-DELETE$ if an existing simple string.
; register HL addresses start of string in variables area.
;; L-ADD$
L2BAF: DEC HL ; point to high byte of length.
DEC HL ; to low byte.
DEC HL ; to letter.
LD A,(HL) ; fetch masked letter to A.
PUSH HL ; save the pointer on stack.
PUSH BC ; save new length.
CALL L2BC6 ; routine L-STRING adds new string at end
; of variables area.
; if no room we still have old one.
POP BC ; restore length.
POP HL ; restore start.
INC BC ; increase
INC BC ; length by three
INC BC ; to include character and length bytes.
JP L19E8 ; jump to indirect exit via RECLAIM-2
; deleting old version and adjusting pointers.
; ---
; the jump was here with a new string variable.
;; L-NEW$
L2BC0: LD A,$DF ; indicator mask %11011111 for
; %010xxxxx will be result
LD HL,($5C4D) ; address DEST first character.
AND (HL) ; combine mask with character.
;; L-STRING
L2BC6: PUSH AF ; save first character and mask.
CALL L2BF1 ; routine STK-FETCH fetches parameters of
; the string.
EX DE,HL ; transfer start to HL.
ADD HL,BC ; add to length.
PUSH BC ; save the length.
DEC HL ; point to end of string.
LD ($5C4D),HL ; save pointer in DEST.
; (updated by POINTERS if in workspace)
INC BC ; extra byte for letter.
INC BC ; two bytes
INC BC ; for the length of string.
LD HL,($5C59) ; address E_LINE.
DEC HL ; now end of VARS area.
CALL L1655 ; routine MAKE-ROOM makes room for string.
; updating pointers including DEST.
LD HL,($5C4D) ; pick up pointer to end of string from DEST.
POP BC ; restore length from stack.
PUSH BC ; and save again on stack.
INC BC ; add a byte.
LDDR ; copy bytes from end to start.
EX DE,HL ; HL addresses length low
INC HL ; increase to address high byte
POP BC ; restore length to BC
LD (HL),B ; insert high byte
DEC HL ; address low byte location
LD (HL),C ; insert that byte
POP AF ; restore character and mask
;; L-FIRST
L2BEA: DEC HL ; address variable name
LD (HL),A ; and insert character.
LD HL,($5C59) ; load HL with E_LINE.
DEC HL ; now end of VARS area.
RET ; return
; ------------------------------------
; Get last value from calculator stack
; ------------------------------------
;
;
;; STK-FETCH
L2BF1: LD HL,($5C65) ; STKEND
DEC HL ;
LD B,(HL) ;
DEC HL ;
LD C,(HL) ;
DEC HL ;
LD D,(HL) ;
DEC HL ;
LD E,(HL) ;
DEC HL ;
LD A,(HL) ;
LD ($5C65),HL ; STKEND
RET ;
; ------------------
; Handle DIM command
; ------------------
; e.g. DIM a(2,3,4,7): DIM a$(32) : DIM b$(300,2,768) : DIM c$(20000)
; the only limit to dimensions is memory so, for example,
; DIM a(2,2,2,2,2,2,2,2,2,2,2,2,2) is possible and creates a multi-
; dimensional array of zeros. String arrays are initialized to spaces.
; It is not possible to erase an array, but it can be re-dimensioned to
; a minimal size of 1, after use, to free up memory.
;; DIM
L2C02: CALL L28B2 ; routine LOOK-VARS
;; D-RPORT-C
L2C05: JP NZ,L1C8A ; jump to REPORT-C if a long-name variable.
; DIM lottery numbers(49) doesn't work.
CALL L2530 ; routine SYNTAX-Z
JR NZ,L2C15 ; forward to D-RUN in runtime.
RES 6,C ; signal 'numeric' array even if string as
; this simplifies the syntax checking.
CALL L2996 ; routine STK-VAR checks syntax.
CALL L1BEE ; routine CHECK-END performs early exit ->
; the branch was here in runtime.
;; D-RUN
L2C15: JR C,L2C1F ; skip to D-LETTER if variable did not exist.
; else reclaim the old one.
PUSH BC ; save type in C.
CALL L19B8 ; routine NEXT-ONE find following variable
; or position of $80 end-marker.
CALL L19E8 ; routine RECLAIM-2 reclaims the
; space between.
POP BC ; pop the type.
;; D-LETTER
L2C1F: SET 7,C ; signal array.
LD B,$00 ; initialize dimensions to zero and
PUSH BC ; save with the type.
LD HL,$0001 ; make elements one character presuming string
BIT 6,C ; is it a string ?
JR NZ,L2C2D ; forward to D-SIZE if so.
LD L,$05 ; make elements 5 bytes as is numeric.
;; D-SIZE
L2C2D: EX DE,HL ; save the element size in DE.
; now enter a loop to parse each of the integers in the list.
;; D-NO-LOOP
L2C2E: RST 20H ; NEXT-CHAR
LD H,$FF ; disable limit check by setting HL high
CALL L2ACC ; routine INT-EXP1
JP C,L2A20 ; to REPORT-3 if > 65280 and then some
; 'Subscript out of range'
POP HL ; pop dimension counter, array type
PUSH BC ; save dimension size ***
INC H ; increment the dimension counter
PUSH HL ; save the dimension counter
LD H,B ; transfer size
LD L,C ; to HL
CALL L2AF4 ; routine GET-HL*DE multiplies dimension by
; running total of size required initially
; 1 or 5.
EX DE,HL ; save running total in DE
RST 18H ; GET-CHAR
CP $2C ; is it ',' ?
JR Z,L2C2E ; loop back to D-NO-LOOP until all dimensions
; have been considered
; when loop complete continue.
CP $29 ; is it ')' ?
JR NZ,L2C05 ; to D-RPORT-C with anything else
; 'Nonsense in BASIC'
RST 20H ; NEXT-CHAR advances to next statement/CR
POP BC ; pop dimension counter/type
LD A,C ; type to A
; now calculate space required for array variable
LD L,B ; dimensions to L since these require 16 bits
; then this value will be doubled
LD H,$00 ; set high byte to zero
; another four bytes are required for letter(1), total length(2), number of
; dimensions(1) but since we have yet to double allow for two
INC HL ; increment
INC HL ; increment
ADD HL,HL ; now double giving 4 + dimensions * 2
ADD HL,DE ; add to space required for array contents
JP C,L1F15 ; to REPORT-4 if > 65535
; 'Out of memory'
PUSH DE ; save data space
PUSH BC ; save dimensions/type
PUSH HL ; save total space
LD B,H ; total space
LD C,L ; to BC
LD HL,($5C59) ; address E_LINE - first location after
; variables area
DEC HL ; point to location before - the $80 end-marker
CALL L1655 ; routine MAKE-ROOM creates the space if
; memory is available.
INC HL ; point to first new location and
LD (HL),A ; store letter/type
POP BC ; pop total space
DEC BC ; exclude name
DEC BC ; exclude the 16-bit
DEC BC ; counter itself
INC HL ; point to next location the 16-bit counter
LD (HL),C ; insert low byte
INC HL ; address next
LD (HL),B ; insert high byte
POP BC ; pop the number of dimensions.
LD A,B ; dimensions to A
INC HL ; address next
LD (HL),A ; and insert "No. of dims"
LD H,D ; transfer DE space + 1 from make-room
LD L,E ; to HL
DEC DE ; set DE to next location down.
LD (HL),$00 ; presume numeric and insert a zero
BIT 6,C ; test bit 6 of C. numeric or string ?
JR Z,L2C7C ; skip to DIM-CLEAR if numeric
LD (HL),$20 ; place a space character in HL
;; DIM-CLEAR
L2C7C: POP BC ; pop the data length
LDDR ; LDDR sets to zeros or spaces
; The number of dimensions is still in A.
; A loop is now entered to insert the size of each dimension that was pushed
; during the D-NO-LOOP working downwards from position before start of data.
;; DIM-SIZES
L2C7F: POP BC ; pop a dimension size ***
LD (HL),B ; insert high byte at position
DEC HL ; next location down
LD (HL),C ; insert low byte
DEC HL ; next location down
DEC A ; decrement dimension counter
JR NZ,L2C7F ; back to DIM-SIZES until all done.
RET ; return.
; -----------------------------
; Check whether digit or letter
; -----------------------------
; This routine checks that the character in A is alphanumeric
; returning with carry set if so.
;; ALPHANUM
L2C88: CALL L2D1B ; routine NUMERIC will reset carry if so.
CCF ; Complement Carry Flag
RET C ; Return if numeric else continue into
; next routine.
; This routine checks that the character in A is alphabetic
;; ALPHA
L2C8D: CP $41 ; less than 'A' ?
CCF ; Complement Carry Flag
RET NC ; return if so
CP $5B ; less than 'Z'+1 ?
RET C ; is within first range
CP $61 ; less than 'a' ?
CCF ; Complement Carry Flag
RET NC ; return if so.
CP $7B ; less than 'z'+1 ?
RET ; carry set if within a-z.
; -------------------------
; Decimal to floating point
; -------------------------
; This routine finds the floating point number represented by an expression
; beginning with BIN, '.' or a digit.
; Note that BIN need not have any '0's or '1's after it.
; BIN is really just a notational symbol and not a function.
;; DEC-TO-FP
L2C9B: CP $C4 ; 'BIN' token ?
JR NZ,L2CB8 ; to NOT-BIN if not
LD DE,$0000 ; initialize 16 bit buffer register.
;; BIN-DIGIT
L2CA2: RST 20H ; NEXT-CHAR
SUB $31 ; '1'
ADC A,$00 ; will be zero if '1' or '0'
; carry will be set if was '0'
JR NZ,L2CB3 ; forward to BIN-END if result not zero
EX DE,HL ; buffer to HL
CCF ; Carry now set if originally '1'
ADC HL,HL ; shift the carry into HL
JP C,L31AD ; to REPORT-6 if overflow - too many digits
; after first '1'. There can be an unlimited
; number of leading zeros.
; 'Number too big' - raise an error
EX DE,HL ; save the buffer
JR L2CA2 ; back to BIN-DIGIT for more digits
; ---
;; BIN-END
L2CB3: LD B,D ; transfer 16 bit buffer
LD C,E ; to BC register pair.
JP L2D2B ; JUMP to STACK-BC to put on calculator stack
; ---
; continue here with .1, 42, 3.14, 5., 2.3 E -4
;; NOT-BIN
L2CB8: CP $2E ; '.' - leading decimal point ?
JR Z,L2CCB ; skip to DECIMAL if so.
CALL L2D3B ; routine INT-TO-FP to evaluate all digits
; This number 'x' is placed on stack.
CP $2E ; '.' - mid decimal point ?
JR NZ,L2CEB ; to E-FORMAT if not to consider that format
RST 20H ; NEXT-CHAR
CALL L2D1B ; routine NUMERIC returns carry reset if 0-9
JR C,L2CEB ; to E-FORMAT if not a digit e.g. '1.'
JR L2CD5 ; to DEC-STO-1 to add the decimal part to 'x'
; ---
; a leading decimal point has been found in a number.
;; DECIMAL
L2CCB: RST 20H ; NEXT-CHAR
CALL L2D1B ; routine NUMERIC will reset carry if digit
;; DEC-RPT-C
L2CCF: JP C,L1C8A ; to REPORT-C if just a '.'
; raise 'Nonsense in BASIC'
; since there is no leading zero put one on the calculator stack.
RST 28H ;; FP-CALC
DB $A0 ;;stk-zero ; 0.
DB $38 ;;end-calc
; If rejoining from earlier there will be a value 'x' on stack.
; If continuing from above the value zero.
; Now store 1 in mem-0.
; Note. At each pass of the digit loop this will be divided by ten.
;; DEC-STO-1
L2CD5: RST 28H ;; FP-CALC
DB $A1 ;;stk-one ;x or 0,1.
DB $C0 ;;st-mem-0 ;x or 0,1.
DB $02 ;;delete ;x or 0.
DB $38 ;;end-calc
;; NXT-DGT-1
L2CDA: RST 18H ; GET-CHAR
CALL L2D22 ; routine STK-DIGIT stacks single digit 'd'
JR C,L2CEB ; exit to E-FORMAT when digits exhausted >
RST 28H ;; FP-CALC ;x or 0,d. first pass.
DB $E0 ;;get-mem-0 ;x or 0,d,1.
DB $A4 ;;stk-ten ;x or 0,d,1,10.
DB $05 ;;division ;x or 0,d,1/10.
DB $C0 ;;st-mem-0 ;x or 0,d,1/10.
DB $04 ;;multiply ;x or 0,d/10.
DB $0F ;;addition ;x or 0 + d/10.
DB $38 ;;end-calc last value.
RST 20H ; NEXT-CHAR moves to next character
JR L2CDA ; back to NXT-DGT-1
; ---
; although only the first pass is shown it can be seen that at each pass
; the new less significant digit is multiplied by an increasingly smaller
; factor (1/100, 1/1000, 1/10000 ... ) before being added to the previous
; last value to form a new last value.
; Finally see if an exponent has been input.
;; E-FORMAT
L2CEB: CP $45 ; is character 'E' ?
JR Z,L2CF2 ; to SIGN-FLAG if so
CP $65 ; 'e' is acceptable as well.
RET NZ ; return as no exponent.
;; SIGN-FLAG
L2CF2: LD B,$FF ; initialize temporary sign byte to $FF
RST 20H ; NEXT-CHAR
CP $2B ; is character '+' ?
JR Z,L2CFE ; to SIGN-DONE
CP $2D ; is character '-' ?
JR NZ,L2CFF ; to ST-E-PART as no sign
INC B ; set sign to zero
; now consider digits of exponent.
; Note. incidentally this is the only occasion in Spectrum BASIC when an
; expression may not be used when a number is expected.
;; SIGN-DONE
L2CFE: RST 20H ; NEXT-CHAR
;; ST-E-PART
L2CFF: CALL L2D1B ; routine NUMERIC
JR C,L2CCF ; to DEC-RPT-C if not
; raise 'Nonsense in BASIC'.
PUSH BC ; save sign (in B)
CALL L2D3B ; routine INT-TO-FP places exponent on stack
CALL L2DD5 ; routine FP-TO-A transfers it to A
POP BC ; restore sign
JP C,L31AD ; to REPORT-6 if overflow (over 255)
; raise 'Number too big'.
AND A ; set flags
JP M,L31AD ; to REPORT-6 if over '127'.
; raise 'Number too big'.
; 127 is still way too high and it is
; impossible to enter an exponent greater
; than 39 from the keyboard. The error gets
; raised later in E-TO-FP so two different
; error messages depending how high A is.
INC B ; $FF to $00 or $00 to $01 - expendable now.
JR Z,L2D18 ; forward to E-FP-JUMP if exponent positive
NEG ; Negate the exponent.
;; E-FP-JUMP
L2D18: JP L2D4F ; JUMP forward to E-TO-FP to assign to
; last value x on stack x * 10 to power A
; a relative jump would have done.
; ---------------------
; Check for valid digit
; ---------------------
; This routine checks that the ASCII character in A is numeric
; returning with carry reset if so.
;; NUMERIC
L2D1B: CP $30 ; '0'
RET C ; return if less than zero character.
CP $3A ; The upper test is '9'
CCF ; Complement Carry Flag
RET ; Return - carry clear if character '0' - '9'
; -----------
; Stack Digit
; -----------
; This subroutine is called from INT-TO-FP and DEC-TO-FP to stack a digit
; on the calculator stack.
;; STK-DIGIT
L2D22: CALL L2D1B ; routine NUMERIC
RET C ; return if not numeric character
SUB $30 ; convert from ASCII to digit
; -----------------
; Stack accumulator
; -----------------
;
;
;; STACK-A
L2D28: LD C,A ; transfer to C
LD B,$00 ; and make B zero
; ----------------------
; Stack BC register pair
; ----------------------
;
;; STACK-BC
L2D2B: LD IY,$5C3A ; re-initialize ERR_NR
XOR A ; clear to signal small integer
LD E,A ; place in E for sign
LD D,C ; LSB to D
LD C,B ; MSB to C
LD B,A ; last byte not used
CALL L2AB6 ; routine STK-STORE
RST 28H ;; FP-CALC
DB $38 ;;end-calc make HL = STKEND-5
AND A ; clear carry
RET ; before returning
; -------------------------
; Integer to floating point
; -------------------------
; This routine places one or more digits found in a BASIC line
; on the calculator stack multiplying the previous value by ten each time
; before adding in the new digit to form a last value on calculator stack.
;; INT-TO-FP
L2D3B: PUSH AF ; save first character
RST 28H ;; FP-CALC
DB $A0 ;;stk-zero ; v=0. initial value
DB $38 ;;end-calc
POP AF ; fetch first character back.
;; NXT-DGT-2
L2D40: CALL L2D22 ; routine STK-DIGIT puts 0-9 on stack
RET C ; will return when character is not numeric >
RST 28H ;; FP-CALC ; v, d.
DB $01 ;;exchange ; d, v.
DB $A4 ;;stk-ten ; d, v, 10.
DB $04 ;;multiply ; d, v*10.
DB $0F ;;addition ; d + v*10 = newvalue
DB $38 ;;end-calc ; v.
CALL L0074 ; routine CH-ADD+1 get next character
JR L2D40 ; back to NXT-DGT-2 to process as a digit
;*********************************
;** Part 9. ARITHMETIC ROUTINES **
;*********************************
; --------------------------
; E-format to floating point
; --------------------------
; This subroutine is used by the PRINT-FP routine and the decimal to FP
; routines to stack a number expressed in exponent format.
; Note. Though not used by the ROM as such, it has also been set up as
; a unary calculator literal but this will not work as the accumulator
; is not available from within the calculator.
; on entry there is a value x on the calculator stack and an exponent of ten
; in A. The required value is x + 10 ^ A
;; e-to-fp
;; E-TO-FP
L2D4F: RLCA ; this will set the x.
RRCA ; carry if bit 7 is set
JR NC,L2D55 ; to E-SAVE if positive.
CPL ; make negative positive
INC A ; without altering carry.
;; E-SAVE
L2D55: PUSH AF ; save positive exp and sign in carry
LD HL,$5C92 ; address MEM-0
CALL L350B ; routine FP-0/1
; places an integer zero, if no carry,
; else a one in mem-0 as a sign flag
RST 28H ;; FP-CALC
DB $A4 ;;stk-ten x, 10.
DB $38 ;;end-calc
POP AF ; pop the exponent.
; now enter a loop
;; E-LOOP
L2D60: SRL A ; 0>76543210>C
JR NC,L2D71 ; forward to E-TST-END if no bit
PUSH AF ; save shifted exponent.
RST 28H ;; FP-CALC
DB $C1 ;;st-mem-1 x, 10.
DB $E0 ;;get-mem-0 x, 10, (0/1).
DB $00 ;;jump-true
DB $04 ;;to L2D6D, E-DIVSN
DB $04 ;;multiply x*10.
DB $33 ;;jump
DB $02 ;;to L2D6E, E-FETCH
;; E-DIVSN
L2D6D: DB $05 ;;division x/10.
;; E-FETCH
L2D6E: DB $E1 ;;get-mem-1 x/10 or x*10, 10.
DB $38 ;;end-calc new x, 10.
POP AF ; restore shifted exponent
; the loop branched to here with no carry
;; E-TST-END
L2D71: JR Z,L2D7B ; forward to E-END if A emptied of bits
PUSH AF ; re-save shifted exponent
RST 28H ;; FP-CALC
DB $31 ;;duplicate new x, 10, 10.
DB $04 ;;multiply new x, 100.
DB $38 ;;end-calc
POP AF ; restore shifted exponent
JR L2D60 ; back to E-LOOP until all bits done.
; ---
; although only the first pass is shown it can be seen that for each set bit
; representing a power of two, x is multiplied or divided by the
; corresponding power of ten.
;; E-END
L2D7B: RST 28H ;; FP-CALC final x, factor.
DB $02 ;;delete final x.
DB $38 ;;end-calc x.
RET ; return
; -------------
; Fetch integer
; -------------
; This routine is called by the mathematical routines - FP-TO-BC, PRINT-FP,
; mult, re-stack and negate to fetch an integer from address HL.
; HL points to the stack or a location in MEM and no deletion occurs.
; If the number is negative then a similar process to that used in INT-STORE
; is used to restore the twos complement number to normal in DE and a sign
; in C.
;; INT-FETCH
L2D7F: INC HL ; skip zero indicator.
LD C,(HL) ; fetch sign to C
INC HL ; address low byte
LD A,(HL) ; fetch to A
XOR C ; two's complement
SUB C ;
LD E,A ; place in E
INC HL ; address high byte
LD A,(HL) ; fetch to A
ADC A,C ; two's complement
XOR C ;
LD D,A ; place in D
RET ; return
; ------------------------
; Store a positive integer
; ------------------------
; This entry point is not used in this ROM but would
; store any integer as positive.
;; p-int-sto
L2D8C: LD C,$00 ; make sign byte positive and continue
; -------------
; Store integer
; -------------
; this routine stores an integer in DE at address HL.
; It is called from mult, truncate, negate and sgn.
; The sign byte $00 +ve or $FF -ve is in C.
; If negative, the number is stored in 2's complement form so that it is
; ready to be added.
;; INT-STORE
L2D8E: PUSH HL ; preserve HL
LD (HL),$00 ; first byte zero shows integer not exponent
INC HL ;
LD (HL),C ; then store the sign byte
INC HL ;
; e.g. +1 -1
LD A,E ; fetch low byte 00000001 00000001
XOR C ; xor sign 00000000 or 11111111
; gives 00000001 or 11111110
SUB C ; sub sign 00000000 or 11111111
; gives 00000001>0 or 11111111>C
LD (HL),A ; store 2's complement.
INC HL ;
LD A,D ; high byte 00000000 00000000
ADC A,C ; sign 00000000<0 11111111<C
; gives 00000000 or 00000000
XOR C ; xor sign 00000000 11111111
LD (HL),A ; store 2's complement.
INC HL ;
LD (HL),$00 ; last byte always zero for integers.
; is not used and need not be looked at when
; testing for zero but comes into play should
; an integer be converted to fp.
POP HL ; restore HL
RET ; return.
; -----------------------------
; Floating point to BC register
; -----------------------------
; This routine gets a floating point number e.g. 127.4 from the calculator
; stack to the BC register.
;; FP-TO-BC
L2DA2: RST 28H ;; FP-CALC set HL to
DB $38 ;;end-calc point to last value.
LD A,(HL) ; get first of 5 bytes
AND A ; and test
JR Z,L2DAD ; forward to FP-DELETE if an integer
; The value is first rounded up and then converted to integer.
RST 28H ;; FP-CALC x.
DB $A2 ;;stk-half x. 1/2.
DB $0F ;;addition x + 1/2.
DB $27 ;;int int(x + .5)
DB $38 ;;end-calc
; now delete but leave HL pointing at integer
;; FP-DELETE
L2DAD: RST 28H ;; FP-CALC
DB $02 ;;delete
DB $38 ;;end-calc
PUSH HL ; save pointer.
PUSH DE ; and STKEND.
EX DE,HL ; make HL point to exponent/zero indicator
LD B,(HL) ; indicator to B
CALL L2D7F ; routine INT-FETCH
; gets int in DE sign byte to C
; but meaningless values if a large integer
XOR A ; clear A
SUB B ; subtract indicator byte setting carry
; if not a small integer.
BIT 7,C ; test a bit of the sign byte setting zero
; if positive.
LD B,D ; transfer int
LD C,E ; to BC
LD A,E ; low byte to A as a useful return value.
POP DE ; pop STKEND
POP HL ; and pointer to last value
RET ; return
; if carry is set then the number was too big.
; ------------
; LOG(2^A)
; ------------
; This routine is used when printing floating point numbers to calculate
; the number of digits before the decimal point.
; first convert a one-byte signed integer to its five byte form.
;; LOG(2^A)
L2DC1: LD D,A ; store a copy of A in D.
RLA ; test sign bit of A.
SBC A,A ; now $FF if negative or $00
LD E,A ; sign byte to E.
LD C,A ; and to C
XOR A ; clear A
LD B,A ; and B.
CALL L2AB6 ; routine STK-STORE stacks number AEDCB
; so 00 00 XX 00 00 (positive) or 00 FF XX FF 00 (negative).
; i.e. integer indicator, sign byte, low, high, unused.
; now multiply exponent by log to the base 10 of two.
RST 28H ;; FP-CALC
DB $34 ;;stk-data .30103 (log 2)
DB $EF ;;Exponent: $7F, Bytes: 4
DB $1A,$20,$9A,$85 ;;
DB $04 ;;multiply
DB $27 ;;int
DB $38 ;;end-calc
; -------------------
; Floating point to A
; -------------------
; this routine collects a floating point number from the stack into the
; accumulator returning carry set if not in range 0 - 255.
; Not all the calling routines raise an error with overflow so no attempt
; is made to produce an error report here.
;; FP-TO-A
L2DD5: CALL L2DA2 ; routine FP-TO-BC returns with C in A also.
RET C ; return with carry set if > 65535, overflow
PUSH AF ; save the value and flags
DEC B ; and test that
INC B ; the high byte is zero.
JR Z,L2DE1 ; forward FP-A-END if zero
; else there has been 8-bit overflow
POP AF ; retrieve the value
SCF ; set carry flag to show overflow
RET ; and return.
; ---
;; FP-A-END
L2DE1: POP AF ; restore value and success flag and
RET ; return.
; -----------------------------
; Print a floating point number
; -----------------------------
; Not a trivial task.
; Begin by considering whether to print a leading sign for negative numbers.
;; PRINT-FP
L2DE3: RST 28H ;; FP-CALC
DB $31 ;;duplicate
DB $36 ;;less-0
DB $00 ;;jump-true
DB $0B ;;to L2DF2, PF-NEGTVE
DB $31 ;;duplicate
DB $37 ;;greater-0
DB $00 ;;jump-true
DB $0D ;;to L2DF8, PF-POSTVE
; must be zero itself
DB $02 ;;delete
DB $38 ;;end-calc
LD A,$30 ; prepare the character '0'
RST 10H ; PRINT-A
RET ; return. ->
; ---
;; PF-NEGTVE
L2DF2: DB $2A ;;abs
DB $38 ;;end-calc
LD A,$2D ; the character '-'
RST 10H ; PRINT-A
; and continue to print the now positive number.
RST 28H ;; FP-CALC
;; PF-POSTVE
L2DF8: DB $A0 ;;stk-zero x,0. begin by
DB $C3 ;;st-mem-3 x,0. clearing a temporary
DB $C4 ;;st-mem-4 x,0. output buffer to
DB $C5 ;;st-mem-5 x,0. fifteen zeros.
DB $02 ;;delete x.
DB $38 ;;end-calc x.
EXX ; in case called from 'str$' then save the
PUSH HL ; pointer to whatever comes after
EXX ; str$ as H'L' will be used.
; now enter a loop?
;; PF-LOOP
L2E01: RST 28H ;; FP-CALC
DB $31 ;;duplicate x,x.
DB $27 ;;int x,int x.
DB $C2 ;;st-mem-2 x,int x.
DB $03 ;;subtract x-int x. fractional part.
DB $E2 ;;get-mem-2 x-int x, int x.
DB $01 ;;exchange int x, x-int x.
DB $C2 ;;st-mem-2 int x, x-int x.
DB $02 ;;delete int x.
DB $38 ;;end-calc int x.
;
; mem-2 holds the fractional part.
; HL points to last value int x
LD A,(HL) ; fetch exponent of int x.
AND A ; test
JR NZ,L2E56 ; forward to PF-LARGE if a large integer
; > 65535
; continue with small positive integer components in range 0 - 65535
; if original number was say .999 then this integer component is zero.
CALL L2D7F ; routine INT-FETCH gets x in DE
; (but x is not deleted)
LD B,$10 ; set B, bit counter, to 16d
LD A,D ; test if
AND A ; high byte is zero
JR NZ,L2E1E ; forward to PF-SAVE if 16-bit integer.
; and continue with integer in range 0 - 255.
OR E ; test the low byte for zero
; i.e. originally just point something or other.
JR Z,L2E24 ; forward if so to PF-SMALL
;
LD D,E ; transfer E to D
LD B,$08 ; and reduce the bit counter to 8.
;; PF-SAVE
L2E1E: PUSH DE ; save the part before decimal point.
EXX ;
POP DE ; and pop in into D'E'
EXX ;
JR L2E7B ; forward to PF-BITS
; ---------------------
; the branch was here when 'int x' was found to be zero as in say 0.5.
; The zero has been fetched from the calculator stack but not deleted and
; this should occur now. This omission leaves the stack unbalanced and while
; that causes no problems with a simple PRINT statement, it will if str$ is
; being used in an expression e.g. "2" + STR$ 0.5 gives the result "0.5"
; instead of the expected result "20.5".
; credit Tony Stratton, 1982.
; A DB 02 delete is required immediately on using the calculator.
;; PF-SMALL
L2E24: RST 28H ;; FP-CALC int x = 0.
L2E25: DB $E2 ;;get-mem-2 int x = 0, x-int x.
DB $38 ;;end-calc
LD A,(HL) ; fetch exponent of positive fractional number
SUB $7E ; subtract
CALL L2DC1 ; routine LOG(2^A) calculates leading digits.
LD D,A ; transfer count to D
LD A,($5CAC) ; fetch total MEM-5-1
SUB D ;
LD ($5CAC),A ; MEM-5-1
LD A,D ;
CALL L2D4F ; routine E-TO-FP
RST 28H ;; FP-CALC
DB $31 ;;duplicate
DB $27 ;;int
DB $C1 ;;st-mem-1
DB $03 ;;subtract
DB $E1 ;;get-mem-1
DB $38 ;;end-calc
CALL L2DD5 ; routine FP-TO-A
PUSH HL ; save HL
LD ($5CA1),A ; MEM-3-1
DEC A ;
RLA ;
SBC A,A ;
INC A ;
LD HL,$5CAB ; address MEM-5-1 leading digit counter
LD (HL),A ; store counter
INC HL ; address MEM-5-2 total digits
ADD A,(HL) ; add counter to contents
LD (HL),A ; and store updated value
POP HL ; restore HL
JP L2ECF ; JUMP forward to PF-FRACTN
; ---
; Note. while it would be pedantic to comment on every occasion a JP
; instruction could be replaced with a JR instruction, this applies to the
; above, which is useful if you wish to correct the unbalanced stack error
; by inserting a 'DB 02 delete' at L2E25, and maintain main addresses.
; the branch was here with a large positive integer > 65535 e.g. 123456789
; the accumulator holds the exponent.
;; PF-LARGE
L2E56: SUB $80 ; make exponent positive
CP $1C ; compare to 28
JR C,L2E6F ; to PF-MEDIUM if integer <= 2^27
CALL L2DC1 ; routine LOG(2^A)
SUB $07 ;
LD B,A ;
LD HL,$5CAC ; address MEM-5-1 the leading digits counter.
ADD A,(HL) ; add A to contents
LD (HL),A ; store updated value.
LD A,B ;
NEG ; negate
CALL L2D4F ; routine E-TO-FP
JR L2E01 ; back to PF-LOOP
; ----------------------------
;; PF-MEDIUM
L2E6F: EX DE,HL ;
CALL L2FBA ; routine FETCH-TWO
EXX ;
SET 7,D ;
LD A,L ;
EXX ;
SUB $80 ;
LD B,A ;
; the branch was here to handle bits in DE with 8 or 16 in B if small int
; and integer in D'E', 6 nibbles will accommodate 065535 but routine does
; 32-bit numbers as well from above
;; PF-BITS
L2E7B: SLA E ; C<xxxxxxxx<0
RL D ; C<xxxxxxxx<C
EXX ;
RL E ; C<xxxxxxxx<C
RL D ; C<xxxxxxxx<C
EXX ;
LD HL,$5CAA ; set HL to mem-4-5th last byte of buffer
LD C,$05 ; set byte count to 5 - 10 nibbles
;; PF-BYTES
L2E8A: LD A,(HL) ; fetch 0 or prev value
ADC A,A ; shift left add in carry C<xxxxxxxx<C
DAA ; Decimal Adjust Accumulator.
; if greater than 9 then the left hand
; nibble is incremented. If greater than
; 99 then adjusted and carry set.
; so if we'd built up 7 and a carry came in
; 0000 0111 < C
; 0000 1111
; daa 1 0101 which is 15 in BCD
LD (HL),A ; put back
DEC HL ; work down thru mem 4
DEC C ; decrease the 5 counter.
JR NZ,L2E8A ; back to PF-BYTES until the ten nibbles rolled
DJNZ L2E7B ; back to PF-BITS until 8 or 16 (or 32) done
; at most 9 digits for 32-bit number will have been loaded with digits
; each of the 9 nibbles in mem 4 is placed into ten bytes in mem-3 and mem 4
; unless the nibble is zero as the buffer is already zero.
; ( or in the case of mem-5 will become zero as a result of RLD instruction )
XOR A ; clear to accept
LD HL,$5CA6 ; address MEM-4-0 byte destination.
LD DE,$5CA1 ; address MEM-3-0 nibble source.
LD B,$09 ; the count is 9 (not ten) as the first
; nibble is known to be blank.
RLD ; shift RH nibble to left in (HL)
; A (HL)
; 0000 0000 < 0000 3210
; 0000 0000 3210 0000
; A picks up the blank nibble
LD C,$FF ; set a flag to indicate when a significant
; digit has been encountered.
;; PF-DIGITS
L2EA1: RLD ; pick up leftmost nibble from (HL)
; A (HL)
; 0000 0000 < 7654 3210
; 0000 7654 3210 0000
JR NZ,L2EA9 ; to PF-INSERT if non-zero value picked up.
DEC C ; test
INC C ; flag
JR NZ,L2EB3 ; skip forward to PF-TEST-2 if flag still $FF
; indicating this is a leading zero.
; but if the zero is a significant digit e.g. 10 then include in digit totals.
; the path for non-zero digits rejoins here.
;; PF-INSERT
L2EA9: LD (DE),A ; insert digit at destination
INC DE ; increase the destination pointer
INC (IY+$71) ; increment MEM-5-1st digit counter
INC (IY+$72) ; increment MEM-5-2nd leading digit counter
LD C,$00 ; set flag to zero indicating that any
; subsequent zeros are significant and not
; leading.
;; PF-TEST-2
L2EB3: BIT 0,B ; test if the nibble count is even
JR Z,L2EB8 ; skip to PF-ALL-9 if so to deal with the
; other nibble in the same byte
INC HL ; point to next source byte if not
;; PF-ALL-9
L2EB8: DJNZ L2EA1 ; decrement the nibble count, back to PF-DIGITS
; if all nine not done.
; For 8-bit integers there will be at most 3 digits.
; For 16-bit integers there will be at most 5 digits.
; but for larger integers there could be nine leading digits.
; if nine digits complete then the last one is rounded up as the number will
; be printed using E-format notation
LD A,($5CAB) ; fetch digit count from MEM-5-1st
SUB $09 ; subtract 9 - max possible
JR C,L2ECB ; forward if less to PF-MORE
DEC (IY+$71) ; decrement digit counter MEM-5-1st to 8
LD A,$04 ; load A with the value 4.
CP (IY+$6F) ; compare with MEM-4-4th - the ninth digit
JR L2F0C ; forward to PF-ROUND
; to consider rounding.
; ---------------------------------------
; now delete int x from calculator stack and fetch fractional part.
;; PF-MORE
L2ECB: RST 28H ;; FP-CALC int x.
DB $02 ;;delete .
DB $E2 ;;get-mem-2 x - int x = f.
DB $38 ;;end-calca f.
;; PF-FRACTN
L2ECF: EX DE,HL ;
CALL L2FBA ; routine FETCH-TWO
EXX ;
LD A,$80 ;
SUB L ;
LD L,$00 ;
SET 7,D ;
EXX ;
CALL L2FDD ; routine SHIFT-FP
;; PF-FRN-LP
L2EDF: LD A,(IY+$71) ; MEM-5-1st
CP $08 ;
JR C,L2EEC ; to PF-FR-DGT
EXX ;
RL D ;
EXX ;
JR L2F0C ; to PF-ROUND
; ---
;; PF-FR-DGT
L2EEC: LD BC,$0200 ;
;; PF-FR-EXX
L2EEF: LD A,E ;
CALL L2F8B ; routine CA-10*A+C
LD E,A ;
LD A,D ;
CALL L2F8B ; routine CA-10*A+C
LD D,A ;
PUSH BC ;
EXX ;
POP BC ;
DJNZ L2EEF ; to PF-FR-EXX
LD HL,$5CA1 ; MEM-3
LD A,C ;
LD C,(IY+$71) ; MEM-5-1st
ADD HL,BC ;
LD (HL),A ;
INC (IY+$71) ; MEM-5-1st
JR L2EDF ; to PF-FRN-LP
; ----------------
; 1) with 9 digits but 8 in mem-5-1 and A holding 4, carry set if rounding up.
; e.g.
; 999999999 is printed as 1E+9
; 100000001 is printed as 1E+8
; 100000009 is printed as 1.0000001E+8
;; PF-ROUND
L2F0C: PUSH AF ; save A and flags
LD HL,$5CA1 ; address MEM-3 start of digits
LD C,(IY+$71) ; MEM-5-1st No. of digits to C
LD B,$00 ; prepare to add
ADD HL,BC ; address last digit + 1
LD B,C ; No. of digits to B counter
POP AF ; restore A and carry flag from comparison.
;; PF-RND-LP
L2F18: DEC HL ; address digit at rounding position.
LD A,(HL) ; fetch it
ADC A,$00 ; add carry from the comparison
LD (HL),A ; put back result even if $0A.
AND A ; test A
JR Z,L2F25 ; skip to PF-R-BACK if ZERO?
CP $0A ; compare to 'ten' - overflow
CCF ; complement carry flag so that set if ten.
JR NC,L2F2D ; forward to PF-COUNT with 1 - 9.
;; PF-R-BACK
L2F25: DJNZ L2F18 ; loop back to PF-RND-LP
; if B counts down to zero then we've rounded right back as in 999999995.
; and the first 8 locations all hold $0A.
LD (HL),$01 ; load first location with digit 1.
INC B ; make B hold 1 also.
; could save an instruction byte here.
INC (IY+$72) ; make MEM-5-2nd hold 1.
; and proceed to initialize total digits to 1.
;; PF-COUNT
L2F2D: LD (IY+$71),B ; MEM-5-1st
; now balance the calculator stack by deleting it
RST 28H ;; FP-CALC
DB $02 ;;delete
DB $38 ;;end-calc
; note if used from str$ then other values may be on the calculator stack.
; we can also restore the next literal pointer from its position on the
; machine stack.
EXX ;
POP HL ; restore next literal pointer.
EXX ;
LD BC,($5CAB) ; set C to MEM-5-1st digit counter.
; set B to MEM-5-2nd leading digit counter.
LD HL,$5CA1 ; set HL to start of digits at MEM-3-1
LD A,B ;
CP $09 ;
JR C,L2F46 ; to PF-NOT-E
CP $FC ;
JR C,L2F6C ; to PF-E-FRMT
;; PF-NOT-E
L2F46: AND A ; test for zero leading digits as in .123
CALL Z,L15EF ; routine OUT-CODE prints a zero e.g. 0.123
;; PF-E-SBRN
L2F4A: XOR A ;
SUB B ;
JP M,L2F52 ; skip forward to PF-OUT-LP if originally +ve
LD B,A ; else negative count now +ve
JR L2F5E ; forward to PF-DC-OUT ->
; ---
;; PF-OUT-LP
L2F52: LD A,C ; fetch total digit count
AND A ; test for zero
JR Z,L2F59 ; forward to PF-OUT-DT if so
LD A,(HL) ; fetch digit
INC HL ; address next digit
DEC C ; decrease total digit counter
;; PF-OUT-DT
L2F59: CALL L15EF ; routine OUT-CODE outputs it.
DJNZ L2F52 ; loop back to PF-OUT-LP until B leading
; digits output.
;; PF-DC-OUT
L2F5E: LD A,C ; fetch total digits and
AND A ; test if also zero
RET Z ; return if so -->
;
INC B ; increment B
LD A,$2E ; prepare the character '.'
;; PF-DEC-0$
L2F64: RST 10H ; PRINT-A outputs the character '.' or '0'
LD A,$30 ; prepare the character '0'
; (for cases like .000012345678)
DJNZ L2F64 ; loop back to PF-DEC-0$ for B times.
LD B,C ; load B with now trailing digit counter.
JR L2F52 ; back to PF-OUT-LP
; ---------------------------------
; the branch was here for E-format printing e.g 123456789 => 1.2345679e+8
;; PF-E-FRMT
L2F6C: LD D,B ; counter to D
DEC D ; decrement
LD B,$01 ; load B with 1.
CALL L2F4A ; routine PF-E-SBRN above
LD A,$45 ; prepare character 'e'
RST 10H ; PRINT-A
LD C,D ; exponent to C
LD A,C ; and to A
AND A ; test exponent
JP P,L2F83 ; to PF-E-POS if positive
NEG ; negate
LD C,A ; positive exponent to C
LD A,$2D ; prepare character '-'
JR L2F85 ; skip to PF-E-SIGN
; ---
;; PF-E-POS
L2F83: LD A,$2B ; prepare character '+'
;; PF-E-SIGN
L2F85: RST 10H ; PRINT-A outputs the sign
LD B,$00 ; make the high byte zero.
JP L1A1B ; exit via OUT-NUM-1 to print exponent in BC
; ------------------------------
; Handle printing floating point
; ------------------------------
; This subroutine is called twice from above when printing floating-point
; numbers. It returns 10*A +C in registers C and A
;; CA-10*A+C
L2F8B: PUSH DE ; preserve DE.
LD L,A ; transfer A to L
LD H,$00 ; zero high byte.
LD E,L ; copy HL
LD D,H ; to DE.
ADD HL,HL ; double (*2)
ADD HL,HL ; double (*4)
ADD HL,DE ; add DE (*5)
ADD HL,HL ; double (*10)
LD E,C ; copy C to E (D is 0)
ADD HL,DE ; and add to give required result.
LD C,H ; transfer to
LD A,L ; destination registers.
POP DE ; restore DE
RET ; return with result.
; --------------
; Prepare to add
; --------------
; This routine is called twice by addition to prepare the two numbers. The
; exponent is picked up in A and the location made zero. Then the sign bit
; is tested before being set to the implied state. Negative numbers are twos
; complemented.
;; PREP-ADD
L2F9B: LD A,(HL) ; pick up exponent
LD (HL),$00 ; make location zero
AND A ; test if number is zero
RET Z ; return if so
INC HL ; address mantissa
BIT 7,(HL) ; test the sign bit
SET 7,(HL) ; set it to implied state
DEC HL ; point to exponent
RET Z ; return if positive number.
PUSH BC ; preserve BC
LD BC,$0005 ; length of number
ADD HL,BC ; point HL past end
LD B,C ; set B to 5 counter
LD C,A ; store exponent in C
SCF ; set carry flag
;; NEG-BYTE
L2FAF: DEC HL ; work from LSB to MSB
LD A,(HL) ; fetch byte
CPL ; complement
ADC A,$00 ; add in initial carry or from prev operation
LD (HL),A ; put back
DJNZ L2FAF ; loop to NEG-BYTE till all 5 done
LD A,C ; stored exponent to A
POP BC ; restore original BC
RET ; return
; -----------------
; Fetch two numbers
; -----------------
; This routine is called twice when printing floating point numbers and also
; to fetch two numbers by the addition, multiply and division routines.
; HL addresses the first number, DE addresses the second number.
; For arithmetic only, A holds the sign of the result which is stored in
; the second location.
;; FETCH-TWO
L2FBA: PUSH HL ; save pointer to first number, result if math.
PUSH AF ; save result sign.
LD C,(HL) ;
INC HL ;
LD B,(HL) ;
LD (HL),A ; store the sign at correct location in
; destination 5 bytes for arithmetic only.
INC HL ;
LD A,C ;
LD C,(HL) ;
PUSH BC ;
INC HL ;
LD C,(HL) ;
INC HL ;
LD B,(HL) ;
EX DE,HL ;
LD D,A ;
LD E,(HL) ;
PUSH DE ;
INC HL ;
LD D,(HL) ;
INC HL ;
LD E,(HL) ;
PUSH DE ;
EXX ;
POP DE ;
POP HL ;
POP BC ;
EXX ;
INC HL ;
LD D,(HL) ;
INC HL ;
LD E,(HL) ;
POP AF ; restore possible result sign.
POP HL ; and pointer to possible result.
RET ; return.
; ---------------------------------
; Shift floating point number right
; ---------------------------------
;
;
;; SHIFT-FP
L2FDD: AND A ;
RET Z ;
CP $21 ;
JR NC,L2FF9 ; to ADDEND-0
PUSH BC ;
LD B,A ;
;; ONE-SHIFT
L2FE5: EXX ;
SRA L ;
RR D ;
RR E ;
EXX ;
RR D ;
RR E ;
DJNZ L2FE5 ; to ONE-SHIFT
POP BC ;
RET NC ;
CALL L3004 ; routine ADD-BACK
RET NZ ;
;; ADDEND-0
L2FF9: EXX ;
XOR A ;
;; ZEROS-4/5
L2FFB: LD L,$00 ;
LD D,A ;
LD E,L ;
EXX ;
LD DE,$0000 ;
RET ;
; ------------------
; Add back any carry
; ------------------
;
;
;; ADD-BACK
L3004: INC E ;
RET NZ ;
INC D ;
RET NZ ;
EXX ;
INC E ;
JR NZ,L300D ; to ALL-ADDED
INC D ;
;; ALL-ADDED
L300D: EXX ;
RET ;
; -----------------------
; Handle subtraction (03)
; -----------------------
; Subtraction is done by switching the sign byte/bit of the second number
; which may be integer of floating point and continuing into addition.
;; subtract
L300F: EX DE,HL ; address second number with HL
CALL L346E ; routine NEGATE switches sign
EX DE,HL ; address first number again
; and continue.
; --------------------
; Handle addition (0F)
; --------------------
; HL points to first number, DE to second.
; If they are both integers, then go for the easy route.
;; addition
L3014: LD A,(DE) ; fetch first byte of second
OR (HL) ; combine with first byte of first
JR NZ,L303E ; forward to FULL-ADDN if at least one was
; in floating point form.
; continue if both were small integers.
PUSH DE ; save pointer to lowest number for result.
INC HL ; address sign byte and
PUSH HL ; push the pointer.
INC HL ; address low byte
LD E,(HL) ; to E
INC HL ; address high byte
LD D,(HL) ; to D
INC HL ; address unused byte
INC HL ; address known zero indicator of 1st number
INC HL ; address sign byte
LD A,(HL) ; sign to A, $00 or $FF
INC HL ; address low byte
LD C,(HL) ; to C
INC HL ; address high byte
LD B,(HL) ; to B
POP HL ; pop result sign pointer
EX DE,HL ; integer to HL
ADD HL,BC ; add to the other one in BC
; setting carry if overflow.
EX DE,HL ; save result in DE bringing back sign pointer
ADC A,(HL) ; if pos/pos A=01 with overflow else 00
; if neg/neg A=FF with overflow else FE
; if mixture A=00 with overflow else FF
RRCA ; bit 0 to (C)
ADC A,$00 ; both acceptable signs now zero
JR NZ,L303C ; forward to ADDN-OFLW if not
SBC A,A ; restore a negative result sign
LD (HL),A ;
INC HL ;
LD (HL),E ;
INC HL ;
LD (HL),D ;
DEC HL ;
DEC HL ;
DEC HL ;
POP DE ; STKEND
RET ;
; ---
;; ADDN-OFLW
L303C: DEC HL ;
POP DE ;
;; FULL-ADDN
L303E: CALL L3293 ; routine RE-ST-TWO
EXX ;
PUSH HL ;
EXX ;
PUSH DE ;
PUSH HL ;
CALL L2F9B ; routine PREP-ADD
LD B,A ;
EX DE,HL ;
CALL L2F9B ; routine PREP-ADD
LD C,A ;
CP B ;
JR NC,L3055 ; to SHIFT-LEN
LD A,B ;
LD B,C ;
EX DE,HL ;
;; SHIFT-LEN
L3055: PUSH AF ;
SUB B ;
CALL L2FBA ; routine FETCH-TWO
CALL L2FDD ; routine SHIFT-FP
POP AF ;
POP HL ;
LD (HL),A ;
PUSH HL ;
LD L,B ;
LD H,C ;
ADD HL,DE ;
EXX ;
EX DE,HL ;
ADC HL,BC ;
EX DE,HL ;
LD A,H ;
ADC A,L ;
LD L,A ;
RRA ;
XOR L ;
EXX ;
EX DE,HL ;
POP HL ;
RRA ;
JR NC,L307C ; to TEST-NEG
LD A,$01 ;
CALL L2FDD ; routine SHIFT-FP
INC (HL) ;
JR Z,L309F ; to ADD-REP-6
;; TEST-NEG
L307C: EXX ;
LD A,L ;
AND $80 ;
EXX ;
INC HL ;
LD (HL),A ;
DEC HL ;
JR Z,L30A5 ; to GO-NC-MLT
LD A,E ;
NEG ; Negate
CCF ; Complement Carry Flag
LD E,A ;
LD A,D ;
CPL ;
ADC A,$00 ;
LD D,A ;
EXX ;
LD A,E ;
CPL ;
ADC A,$00 ;
LD E,A ;
LD A,D ;
CPL ;
ADC A,$00 ;
JR NC,L30A3 ; to END-COMPL
RRA ;
EXX ;
INC (HL) ;
;; ADD-REP-6
L309F: JP Z,L31AD ; to REPORT-6
EXX ;
;; END-COMPL
L30A3: LD D,A ;
EXX ;
;; GO-NC-MLT
L30A5: XOR A ;
JP L3155 ; to TEST-NORM
; -----------------------------
; Used in 16 bit multiplication
; -----------------------------
; This routine is used, in the first instance, by the multiply calculator
; literal to perform an integer multiplication in preference to
; 32-bit multiplication to which it will resort if this overflows.
;
; It is also used by STK-VAR to calculate array subscripts and by DIM to
; calculate the space required for multi-dimensional arrays.
;; HL-HL*DE
L30A9: PUSH BC ; preserve BC throughout
LD B,$10 ; set B to 16
LD A,H ; save H in A high byte
LD C,L ; save L in C low byte
LD HL,$0000 ; initialize result to zero
; now enter a loop.
;; HL-LOOP
L30B1: ADD HL,HL ; double result
JR C,L30BE ; to HL-END if overflow
RL C ; shift AC left into carry
RLA ;
JR NC,L30BC ; to HL-AGAIN to skip addition if no carry
ADD HL,DE ; add in DE
JR C,L30BE ; to HL-END if overflow
;; HL-AGAIN
L30BC: DJNZ L30B1 ; back to HL-LOOP for all 16 bits
;; HL-END
L30BE: POP BC ; restore preserved BC
RET ; return with carry reset if successful
; and result in HL.
; -----------------------------
; Prepare to multiply or divide
; -----------------------------
; This routine is called in succession from multiply and divide to prepare
; two mantissas by setting the leftmost bit that is used for the sign.
; On the first call A holds zero and picks up the sign bit. On the second
; call the two bits are XORed to form the result sign - minus * minus giving
; plus etc. If either number is zero then this is flagged.
; HL addresses the exponent.
;; PREP-M/D
L30C0: CALL L34E9 ; routine TEST-ZERO preserves accumulator.
RET C ; return carry set if zero
INC HL ; address first byte of mantissa
XOR (HL) ; pick up the first or xor with first.
SET 7,(HL) ; now set to give true 32-bit mantissa
DEC HL ; point to exponent
RET ; return with carry reset
; --------------------------
; Handle multiplication (04)
; --------------------------
;
;
;; multiply
L30CA: LD A,(DE) ;
OR (HL) ;
JR NZ,L30F0 ; to MULT-LONG
PUSH DE ;
PUSH HL ;
PUSH DE ;
CALL L2D7F ; routine INT-FETCH
EX DE,HL ;
EX (SP),HL ;
LD B,C ;
CALL L2D7F ; routine INT-FETCH
LD A,B ;
XOR C ;
LD C,A ;
POP HL ;
CALL L30A9 ; routine HL-HL*DE
EX DE,HL ;
POP HL ;
JR C,L30EF ; to MULT-OFLW
LD A,D ;
OR E ;
JR NZ,L30EA ; to MULT-RSLT
LD C,A ;
;; MULT-RSLT
L30EA: CALL L2D8E ; routine INT-STORE
POP DE ;
RET ;
; ---
;; MULT-OFLW
L30EF: POP DE ;
;; MULT-LONG
L30F0: CALL L3293 ; routine RE-ST-TWO
XOR A ;
CALL L30C0 ; routine PREP-M/D
RET C ;
EXX ;
PUSH HL ;
EXX ;
PUSH DE ;
EX DE,HL ;
CALL L30C0 ; routine PREP-M/D
EX DE,HL ;
JR C,L315D ; to ZERO-RSLT
PUSH HL ;
CALL L2FBA ; routine FETCH-TWO
LD A,B ;
AND A ;
SBC HL,HL ;
EXX ;
PUSH HL ;
SBC HL,HL ;
EXX ;
LD B,$21 ;
JR L3125 ; to STRT-MLT
; ---
;; MLT-LOOP
L3114: JR NC,L311B ; to NO-ADD
ADD HL,DE ;
EXX ;
ADC HL,DE ;
EXX ;
;; NO-ADD
L311B: EXX ;
RR H ;
RR L ;
EXX ;
RR H ;
RR L ;
;; STRT-MLT
L3125: EXX ;
RR B ;
RR C ;
EXX ;
RR C ;
RRA ;
DJNZ L3114 ; to MLT-LOOP
EX DE,HL ;
EXX ;
EX DE,HL ;
EXX ;
POP BC ;
POP HL ;
LD A,B ;
ADD A,C ;
JR NZ,L313B ; to MAKE-EXPT
AND A ;
;; MAKE-EXPT
L313B: DEC A ;
CCF ; Complement Carry Flag
;; DIVN-EXPT
L313D: RLA ;
CCF ; Complement Carry Flag
RRA ;
JP P,L3146 ; to OFLW1-CLR
JR NC,L31AD ; to REPORT-6
AND A ;
;; OFLW1-CLR
L3146: INC A ;
JR NZ,L3151 ; to OFLW2-CLR
JR C,L3151 ; to OFLW2-CLR
EXX ;
BIT 7,D ;
EXX ;
JR NZ,L31AD ; to REPORT-6
;; OFLW2-CLR
L3151: LD (HL),A ;
EXX ;
LD A,B ;
EXX ;
;; TEST-NORM
L3155: JR NC,L316C ; to NORMALISE
LD A,(HL) ;
AND A ;
;; NEAR-ZERO
L3159: LD A,$80 ;
JR Z,L315E ; to SKIP-ZERO
;; ZERO-RSLT
L315D: XOR A ;
;; SKIP-ZERO
L315E: EXX ;
AND D ;
CALL L2FFB ; routine ZEROS-4/5
RLCA ;
LD (HL),A ;
JR C,L3195 ; to OFLOW-CLR
INC HL ;
LD (HL),A ;
DEC HL ;
JR L3195 ; to OFLOW-CLR
; ---
;; NORMALISE
L316C: LD B,$20 ;
;; SHIFT-ONE
L316E: EXX ;
BIT 7,D ;
EXX ;
JR NZ,L3186 ; to NORML-NOW
RLCA ;
RL E ;
RL D ;
EXX ;
RL E ;
RL D ;
EXX ;
DEC (HL) ;
JR Z,L3159 ; to NEAR-ZERO
DJNZ L316E ; to SHIFT-ONE
JR L315D ; to ZERO-RSLT
; ---
;; NORML-NOW
L3186: RLA ;
JR NC,L3195 ; to OFLOW-CLR
CALL L3004 ; routine ADD-BACK
JR NZ,L3195 ; to OFLOW-CLR
EXX ;
LD D,$80 ;
EXX ;
INC (HL) ;
JR Z,L31AD ; to REPORT-6
;; OFLOW-CLR
L3195: PUSH HL ;
INC HL ;
EXX ;
PUSH DE ;
EXX ;
POP BC ;
LD A,B ;
RLA ;
RL (HL) ;
RRA ;
LD (HL),A ;
INC HL ;
LD (HL),C ;
INC HL ;
LD (HL),D ;
INC HL ;
LD (HL),E ;
POP HL ;
POP DE ;
EXX ;
POP HL ;
EXX ;
RET ;
; ---
;; REPORT-6
L31AD: RST 08H ; ERROR-1
DB $05 ; Error Report: Number too big
; --------------------
; Handle division (05)
; --------------------
;
;
;; division
L31AF: CALL L3293 ; routine RE-ST-TWO
EX DE,HL ;
XOR A ;
CALL L30C0 ; routine PREP-M/D
JR C,L31AD ; to REPORT-6
EX DE,HL ;
CALL L30C0 ; routine PREP-M/D
RET C ;
EXX ;
PUSH HL ;
EXX ;
PUSH DE ;
PUSH HL ;
CALL L2FBA ; routine FETCH-TWO
EXX ;
PUSH HL ;
LD H,B ;
LD L,C ;
EXX ;
LD H,C ;
LD L,B ;
XOR A ;
LD B,$DF ;
JR L31E2 ; to DIV-START
; ---
;; DIV-LOOP
L31D2: RLA ;
RL C ;
EXX ;
RL C ;
RL B ;
EXX ;
;; div-34th
L31DB: ADD HL,HL ;
EXX ;
ADC HL,HL ;
EXX ;
JR C,L31F2 ; to SUBN-ONLY
;; DIV-START
L31E2: SBC HL,DE ;
EXX ;
SBC HL,DE ;
EXX ;
JR NC,L31F9 ; to NO-RSTORE
ADD HL,DE ;
EXX ;
ADC HL,DE ;
EXX ;
AND A ;
JR L31FA ; to COUNT-ONE
; ---
;; SUBN-ONLY
L31F2: AND A ;
SBC HL,DE ;
EXX ;
SBC HL,DE ;
EXX ;
;; NO-RSTORE
L31F9: SCF ; Set Carry Flag
;; COUNT-ONE
L31FA: INC B ;
JP M,L31D2 ; to DIV-LOOP
PUSH AF ;
JR Z,L31E2 ; to DIV-START
;
;
;
;
LD E,A ;
LD D,C ;
EXX ;
LD E,C ;
LD D,B ;
POP AF ;
RR B ;
POP AF ;
RR B ;
EXX ;
POP BC ;
POP HL ;
LD A,B ;
SUB C ;
JP L313D ; jump back to DIVN-EXPT
; ------------------------------------
; Integer truncation towards zero ($3A)
; ------------------------------------
;
;
;; truncate
L3214: LD A,(HL) ;
AND A ;
RET Z ;
CP $81 ;
JR NC,L3221 ; to T-GR-ZERO
LD (HL),$00 ;
LD A,$20 ;
JR L3272 ; to NIL-BYTES
; ---
;; T-GR-ZERO
L3221: CP $91 ;
JR NZ,L323F ; to T-SMALL
INC HL ;
INC HL ;
INC HL ;
LD A,$80 ;
AND (HL) ;
DEC HL ;
OR (HL) ;
DEC HL ;
JR NZ,L3233 ; to T-FIRST
LD A,$80 ;
XOR (HL) ;
;; T-FIRST
L3233: DEC HL ;
JR NZ,L326C ; to T-EXPNENT
LD (HL),A ;
INC HL ;
LD (HL),$FF ;
DEC HL ;
LD A,$18 ;
JR L3272 ; to NIL-BYTES
; ---
;; T-SMALL
L323F: JR NC,L326D ; to X-LARGE
PUSH DE ;
CPL ;
ADD A,$91 ;
INC HL ;
LD D,(HL) ;
INC HL ;
LD E,(HL) ;
DEC HL ;
DEC HL ;
LD C,$00 ;
BIT 7,D ;
JR Z,L3252 ; to T-NUMERIC
DEC C ;
;; T-NUMERIC
L3252: SET 7,D ;
LD B,$08 ;
SUB B ;
ADD A,B ;
JR C,L325E ; to T-TEST
LD E,D ;
LD D,$00 ;
SUB B ;
;; T-TEST
L325E: JR Z,L3267 ; to T-STORE
LD B,A ;
;; T-SHIFT
L3261: SRL D ;
RR E ;
DJNZ L3261 ; to T-SHIFT
;; T-STORE
L3267: CALL L2D8E ; routine INT-STORE
POP DE ;
RET ;
; ---
;; T-EXPNENT
L326C: LD A,(HL) ;
;; X-LARGE
L326D: SUB $A0 ;
RET P ;
NEG ; Negate
;; NIL-BYTES
L3272: PUSH DE ;
EX DE,HL ;
DEC HL ;
LD B,A ;
SRL B ;
SRL B ;
SRL B ;
JR Z,L3283 ; to BITS-ZERO
;; BYTE-ZERO
L327E: LD (HL),$00 ;
DEC HL ;
DJNZ L327E ; to BYTE-ZERO
;; BITS-ZERO
L3283: AND $07 ;
JR Z,L3290 ; to IX-END
LD B,A ;
LD A,$FF ;
;; LESS-MASK
L328A: SLA A ;
DJNZ L328A ; to LESS-MASK
AND (HL) ;
LD (HL),A ;
;; IX-END
L3290: EX DE,HL ;
POP DE ;
RET ;
; ----------------------------------
; Storage of numbers in 5 byte form.
; ==================================
; Both integers and floating-point numbers can be stored in five bytes.
; Zero is a special case stored as 5 zeros.
; For integers the form is
; Byte 1 - zero,
; Byte 2 - sign byte, $00 +ve, $FF -ve.
; Byte 3 - Low byte of integer.
; Byte 4 - High byte
; Byte 5 - unused but always zero.
;
; it seems unusual to store the low byte first but it is just as easy either
; way. Statistically it just increases the chances of trailing zeros which
; is an advantage elsewhere in saving ROM code.
;
; zero sign low high unused
; So +1 is 00000000 00000000 00000001 00000000 00000000
;
; and -1 is 00000000 11111111 11111111 11111111 00000000
;
; much of the arithmetic found in BASIC lines can be done using numbers
; in this form using the Z80's 16 bit register operation ADD.
; (multiplication is done by a sequence of additions).
;
; Storing -ve integers in two's complement form, means that they are ready for
; addition and you might like to add the numbers above to prove that the
; answer is zero. If, as in this case, the carry is set then that denotes that
; the result is positive. This only applies when the signs don't match.
; With positive numbers a carry denotes the result is out of integer range.
; With negative numbers a carry denotes the result is within range.
; The exception to the last rule is when the result is -65536
;
; Floating point form is an alternative method of storing numbers which can
; be used for integers and larger (or fractional) numbers.
;
; In this form 1 is stored as
; 10000001 00000000 00000000 00000000 00000000
;
; When a small integer is converted to a floating point number the last two
; bytes are always blank so they are omitted in the following steps
;
; first make exponent +1 +16d (bit 7 of the exponent is set if positive)
; 10010001 00000000 00000001
; 10010000 00000000 00000010 <- now shift left and decrement exponent
; ...
; 10000010 01000000 00000000 <- until a 1 abuts the imaginary point
; 10000001 10000000 00000000 to the left of the mantissa.
;
; however since the leftmost bit of the mantissa is always set then it can
; be used to denote the sign of the mantissa and put back when needed by the
; PREP routines which gives
;
; 10000001 00000000 00000000
; -----------------------------
; Re-stack two `small' integers
; -----------------------------
; This routine is called to re-stack two numbers in full floating point form
; e.g. from mult when integer multiplication has overflowed.
;; RE-ST-TWO
L3293: CALL L3296 ; routine RESTK-SUB below and continue
; into the routine to do the other one.
;; RESTK-SUB
L3296: EX DE,HL ; swap pointers
; --------------------------------
; Re-stack one number in full form
; --------------------------------
; This routine re-stacks an integer usually on the calculator stack
; in full floating point form.
; HL points to first byte.
;; re-stack
L3297: LD A,(HL) ; Fetch Exponent byte to A
AND A ; test it
RET NZ ; return if not zero as already in full
; floating-point form.
PUSH DE ; preserve DE.
CALL L2D7F ; routine INT-FETCH
; integer to DE, sign to C.
; HL points to 4th byte.
XOR A ; clear accumulator.
INC HL ; point to 5th.
LD (HL),A ; and blank.
DEC HL ; point to 4th.
LD (HL),A ; and blank.
LD B,$91 ; set exponent byte +ve $81
; and imaginary dec point 16 bits to right
; of first bit.
; we could skip to normalize now but it's quicker to avoid
; normalizing through an empty D.
LD A,D ; fetch the high byte D
AND A ; is it zero ?
JR NZ,L32B1 ; skip to RS-NRMLSE if not.
OR E ; low byte E to A and test for zero
LD B,D ; set B exponent to 0
JR Z,L32BD ; forward to RS-STORE if value is zero.
LD D,E ; transfer E to D
LD E,B ; set E to 0
LD B,$89 ; reduce the initial exponent by eight.
;; RS-NRMLSE
L32B1: EX DE,HL ; integer to HL, addr of 4th byte to DE.
;; RSTK-LOOP
L32B2: DEC B ; decrease exponent
ADD HL,HL ; shift DE left
JR NC,L32B2 ; loop back to RSTK-LOOP
; until a set bit pops into carry
RRC C ; now rotate the sign byte $00 or $FF
; into carry to give a sign bit
RR H ; rotate the sign bit to left of H
RR L ; rotate any carry into L
EX DE,HL ; address 4th byte, normalized int to DE
;; RS-STORE
L32BD: DEC HL ; address 3rd byte
LD (HL),E ; place E
DEC HL ; address 2nd byte
LD (HL),D ; place D
DEC HL ; address 1st byte
LD (HL),B ; store the exponent
POP DE ; restore initial DE.
RET ; return.
;****************************************
;** Part 10. FLOATING-POINT CALCULATOR **
;****************************************
; As a general rule the calculator avoids using the IY register.
; exceptions are val, val$ and str$.
; So an assembly language programmer who has disabled interrupts to use
; IY for other purposes can still use the calculator for mathematical
; purposes.
; ------------------
; Table of constants
; ------------------
;
;
; used 11 times
;; stk-zero 00 00 00 00 00
L32C5: DB $00 ;;Bytes: 1
DB $B0 ;;Exponent $00
DB $00 ;;(+00,+00,+00)
; used 19 times
;; stk-one 00 00 01 00 00
L32C8: DB $40 ;;Bytes: 2
DB $B0 ;;Exponent $00
DB $00,$01 ;;(+00,+00)
; used 9 times
;; stk-half 80 00 00 00 00
L32CC: DB $30 ;;Exponent: $80, Bytes: 1
DB $00 ;;(+00,+00,+00)
; used 4 times.
;; stk-pi/2 81 49 0F DA A2
L32CE: DB $F1 ;;Exponent: $81, Bytes: 4
DB $49,$0F,$DA,$A2 ;;
; used 3 times.
;; stk-ten 00 00 0A 00 00
L32D3: DB $40 ;;Bytes: 2
DB $B0 ;;Exponent $00
DB $00,$0A ;;(+00,+00)
; ------------------
; Table of addresses
; ------------------
;
; starts with binary operations which have two operands and one result.
; three pseudo binary operations first.
;; tbl-addrs
L32D7: DEFW L368F ; $00 Address: $368F - jump-true
DEFW L343C ; $01 Address: $343C - exchange
DEFW L33A1 ; $02 Address: $33A1 - delete
; true binary operations.
DEFW L300F ; $03 Address: $300F - subtract
DEFW L30CA ; $04 Address: $30CA - multiply
DEFW L31AF ; $05 Address: $31AF - division
DEFW L3851 ; $06 Address: $3851 - to-power
DEFW L351B ; $07 Address: $351B - or
DEFW L3524 ; $08 Address: $3524 - no-&-no
DEFW L353B ; $09 Address: $353B - no-l-eql
DEFW L353B ; $0A Address: $353B - no-gr-eql
DEFW L353B ; $0B Address: $353B - nos-neql
DEFW L353B ; $0C Address: $353B - no-grtr
DEFW L353B ; $0D Address: $353B - no-less
DEFW L353B ; $0E Address: $353B - nos-eql
DEFW L3014 ; $0F Address: $3014 - addition
DEFW L352D ; $10 Address: $352D - str-&-no
DEFW L353B ; $11 Address: $353B - str-l-eql
DEFW L353B ; $12 Address: $353B - str-gr-eql
DEFW L353B ; $13 Address: $353B - strs-neql
DEFW L353B ; $14 Address: $353B - str-grtr
DEFW L353B ; $15 Address: $353B - str-less
DEFW L353B ; $16 Address: $353B - strs-eql
DEFW L359C ; $17 Address: $359C - strs-add
; unary follow
DEFW L35DE ; $18 Address: $35DE - val$
DEFW L34BC ; $19 Address: $34BC - usr-$
DEFW L3645 ; $1A Address: $3645 - read-in
DEFW L346E ; $1B Address: $346E - negate
DEFW L3669 ; $1C Address: $3669 - code
DEFW L35DE ; $1D Address: $35DE - val
DEFW L3674 ; $1E Address: $3674 - len
DEFW L37B5 ; $1F Address: $37B5 - sin
DEFW L37AA ; $20 Address: $37AA - cos
DEFW L37DA ; $21 Address: $37DA - tan
DEFW L3833 ; $22 Address: $3833 - asn
DEFW L3843 ; $23 Address: $3843 - acs
DEFW L37E2 ; $24 Address: $37E2 - atn
DEFW L3713 ; $25 Address: $3713 - ln
DEFW L36C4 ; $26 Address: $36C4 - exp
DEFW L36AF ; $27 Address: $36AF - int
DEFW L384A ; $28 Address: $384A - sqr
DEFW L3492 ; $29 Address: $3492 - sgn
DEFW L346A ; $2A Address: $346A - abs
DEFW L34AC ; $2B Address: $34AC - peek
DEFW L34A5 ; $2C Address: $34A5 - in
DEFW L34B3 ; $2D Address: $34B3 - usr-no
DEFW L361F ; $2E Address: $361F - str$
DEFW L35C9 ; $2F Address: $35C9 - chrs
DEFW L3501 ; $30 Address: $3501 - not
; end of true unary
DEFW L33C0 ; $31 Address: $33C0 - duplicate
DEFW L36A0 ; $32 Address: $36A0 - n-mod-m
DEFW L3686 ; $33 Address: $3686 - jump
DEFW L33C6 ; $34 Address: $33C6 - stk-data
DEFW L367A ; $35 Address: $367A - dec-jr-nz
DEFW L3506 ; $36 Address: $3506 - less-0
DEFW L34F9 ; $37 Address: $34F9 - greater-0
DEFW L369B ; $38 Address: $369B - end-calc
DEFW L3783 ; $39 Address: $3783 - get-argt
DEFW L3214 ; $3A Address: $3214 - truncate
DEFW L33A2 ; $3B Address: $33A2 - fp-calc-2
DEFW L2D4F ; $3C Address: $2D4F - e-to-fp
DEFW L3297 ; $3D Address: $3297 - re-stack
; the following are just the next available slots for the 128 compound literals
; which are in range $80 - $FF.
DEFW L3449 ; $3E Address: $3449 - series-xx $80 - $9F.
DEFW L341B ; $3F Address: $341B - stk-const-xx $A0 - $BF.
DEFW L342D ; $40 Address: $342D - st-mem-xx $C0 - $DF.
DEFW L340F ; $41 Address: $340F - get-mem-xx $E0 - $FF.
; Aside: 3E - 7F are therefore unused calculator literals.
; 3E - 7B would be available for expansion.
; --------------
; The Calculator
; --------------
;
;
;; CALCULATE
L335B: CALL L35BF ; routine STK-PNTRS is called to set up the
; calculator stack pointers for a default
; unary operation. HL = last value on stack.
; DE = STKEND first location after stack.
; the calculate routine is called at this point by the series generator...
;; GEN-ENT-1
L335E: LD A,B ; fetch the Z80 B register to A
LD ($5C67),A ; and store value in system variable BREG.
; this will be the counter for dec-jr-nz
; or if used from fp-calc2 the calculator
; instruction.
; ... and again later at this point
;; GEN-ENT-2
L3362: EXX ; switch sets
EX (SP),HL ; and store the address of next instruction,
; the return address, in H'L'.
; If this is a recursive call the the H'L'
; of the previous invocation goes on stack.
; c.f. end-calc.
EXX ; switch back to main set
; this is the re-entry looping point when handling a string of literals.
;; RE-ENTRY
L3365: LD ($5C65),DE ; save end of stack in system variable STKEND
EXX ; switch to alt
LD A,(HL) ; get next literal
INC HL ; increase pointer'
; single operation jumps back to here
;; SCAN-ENT
L336C: PUSH HL ; save pointer on stack
AND A ; now test the literal
JP P,L3380 ; forward to FIRST-3D if in range $00 - $3D
; anything with bit 7 set will be one of
; 128 compound literals.
; compound literals have the following format.
; bit 7 set indicates compound.
; bits 6-5 the subgroup 0-3.
; bits 4-0 the embedded parameter $00 - $1F.
; The subgroup 0-3 needs to be manipulated to form the next available four
; address places after the simple literals in the address table.
LD D,A ; save literal in D
AND $60 ; and with 01100000 to isolate subgroup
RRCA ; rotate bits
RRCA ; 4 places to right
RRCA ; not five as we need offset * 2
RRCA ; 00000xx0
ADD A,$7C ; add ($3E * 2) to give correct offset.
; alter above if you add more literals.
LD L,A ; store in L for later indexing.
LD A,D ; bring back compound literal
AND $1F ; use mask to isolate parameter bits
JR L338E ; forward to ENT-TABLE
; ---
; the branch was here with simple literals.
;; FIRST-3D
L3380: CP $18 ; compare with first unary operations.
JR NC,L338C ; to DOUBLE-A with unary operations
; it is binary so adjust pointers.
EXX ;
LD BC,$FFFB ; the value -5
LD D,H ; transfer HL, the last value, to DE.
LD E,L ;
ADD HL,BC ; subtract 5 making HL point to second
; value.
EXX ;
;; DOUBLE-A
L338C: RLCA ; double the literal
LD L,A ; and store in L for indexing
;; ENT-TABLE
L338E: LD DE,L32D7 ; Address: tbl-addrs
LD H,$00 ; prepare to index
ADD HL,DE ; add to get address of routine
LD E,(HL) ; low byte to E
INC HL ;
LD D,(HL) ; high byte to D
LD HL,L3365 ; Address: RE-ENTRY
EX (SP),HL ; goes to stack
PUSH DE ; now address of routine
EXX ; main set
; avoid using IY register.
LD BC,($5C66) ; STKEND_hi
; nothing much goes to C but BREG to B
; and continue into next ret instruction
; which has a dual identity
; ------------------
; Handle delete (02)
; ------------------
; A simple return but when used as a calculator literal this
; deletes the last value from the calculator stack.
; On entry, as always with binary operations,
; HL=first number, DE=second number
; On exit, HL=result, DE=stkend.
; So nothing to do
;; delete
L33A1: RET ; return - indirect jump if from above.
; ---------------------
; Single operation (3B)
; ---------------------
; this single operation is used, in the first instance, to evaluate most
; of the mathematical and string functions found in BASIC expressions.
;; fp-calc-2
L33A2: POP AF ; drop return address.
LD A,($5C67) ; load accumulator from system variable BREG
; value will be literal eg. 'tan'
EXX ; switch to alt
JR L336C ; back to SCAN-ENT
; next literal will be end-calc at L2758
; ----------------
; Test five-spaces
; ----------------
; This routine is called from MOVE-FP, STK-CONST and STK-STORE to
; test that there is enough space between the calculator stack and the
; machine stack for another five-byte value. It returns with BC holding
; the value 5 ready for any subsequent LDIR.
;; TEST-5-SP
L33A9: PUSH DE ; save
PUSH HL ; registers
LD BC,$0005 ; an overhead of five bytes
CALL L1F05 ; routine TEST-ROOM tests free RAM raising
; an error if not.
POP HL ; else restore
POP DE ; registers.
RET ; return with BC set at 5.
; ------------
; Stack number
; ------------
; This routine is called to stack a hidden floating point number found in
; a BASIC line. It is also called to stack a numeric variable value, and
; from BEEP, to stack an entry in the semi-tone table. It is not part of the
; calculator suite of routines.
; On entry HL points to the number to be stacked.
;; STACK-NUM
L33B4: LD DE,($5C65) ; load destination from STKEND system variable.
CALL L33C0 ; routine MOVE-FP puts on calculator stack
; with a memory check.
LD ($5C65),DE ; set STKEND to next free location.
RET ; return.
; ---------------------------------
; Move a floating point number (31)
; ---------------------------------
; This simple routine is a 5-byte LDIR instruction
; that incorporates a memory check.
; When used as a calculator literal it duplicates the last value on the
; calculator stack.
; Unary so on entry HL points to last value, DE to stkend
;; duplicate
;; MOVE-FP
L33C0: CALL L33A9 ; routine TEST-5-SP test free memory
; and sets BC to 5.
LDIR ; copy the five bytes.
RET ; return with DE addressing new STKEND
; and HL addressing new last value.
; -------------------
; Stack literals ($34)
; -------------------
; When a calculator subroutine needs to put a value on the calculator
; stack that is not a regular constant this routine is called with a
; variable number of following data bytes that convey to the routine
; the integer or floating point form as succinctly as is possible.
;; stk-data
L33C6: LD H,D ; transfer STKEND
LD L,E ; to HL for result.
;; STK-CONST
L33C8: CALL L33A9 ; routine TEST-5-SP tests that room exists
; and sets BC to $05.
EXX ; switch to alternate set
PUSH HL ; save the pointer to next literal on stack
EXX ; switch back to main set
EX (SP),HL ; pointer to HL, destination to stack.
PUSH BC ; save BC - value 5 from test room ??.
LD A,(HL) ; fetch the byte following 'stk-data'
AND $C0 ; isolate bits 7 and 6
RLCA ; rotate
RLCA ; to bits 1 and 0 range $00 - $03.
LD C,A ; transfer to C
INC C ; and increment to give number of bytes
; to read. $01 - $04
LD A,(HL) ; reload the first byte
AND $3F ; mask off to give possible exponent.
JR NZ,L33DE ; forward to FORM-EXP if it was possible to
; include the exponent.
; else byte is just a byte count and exponent comes next.
INC HL ; address next byte and
LD A,(HL) ; pick up the exponent ( - $50).
;; FORM-EXP
L33DE: ADD A,$50 ; now add $50 to form actual exponent
LD (DE),A ; and load into first destination byte.
LD A,$05 ; load accumulator with $05 and
SUB C ; subtract C to give count of trailing
; zeros plus one.
INC HL ; increment source
INC DE ; increment destination
LD B,$00 ; prepare to copy
LDIR ; copy C bytes
POP BC ; restore 5 counter to BC ??.
EX (SP),HL ; put HL on stack as next literal pointer
; and the stack value - result pointer -
; to HL.
EXX ; switch to alternate set.
POP HL ; restore next literal pointer from stack
; to H'L'.
EXX ; switch back to main set.
LD B,A ; zero count to B
XOR A ; clear accumulator
;; STK-ZEROS
L33F1: DEC B ; decrement B counter
RET Z ; return if zero. >>
; DE points to new STKEND
; HL to new number.
LD (DE),A ; else load zero to destination
INC DE ; increase destination
JR L33F1 ; loop back to STK-ZEROS until done.
; -------------------------------
; THE 'SKIP CONSTANTS' SUBROUTINE
; -------------------------------
; This routine traverses variable-length entries in the table of constants,
; stacking intermediate, unwanted constants onto a dummy calculator stack,
; in the first five bytes of ROM. The destination DE normally points to the
; end of the calculator stack which might be in the normal place or in the
; system variables area during E-LINE-NO; INT-TO-FP; stk-ten. In any case,
; it would be simpler all round if the routine just shoved unwanted values
; where it is going to stick the wanted value.
; The instruction LD DE, $0000 can be removed.
;; SKIP-CONS
L33F7: AND A ; test if initially zero.
;; SKIP-NEXT
L33F8: RET Z ; return if zero. >>
PUSH AF ; save count.
PUSH DE ; and normal STKEND
LD DE,$0000 ; dummy value for STKEND at start of ROM
; Note. not a fault but this has to be
; moved elsewhere when running in RAM.
; e.g. with Expandor Systems 'Soft ROM'.
; Better still, write to the normal place.
CALL L33C8 ; routine STK-CONST works through variable
; length records.
POP DE ; restore real STKEND
POP AF ; restore count
DEC A ; decrease
JR L33F8 ; loop back to SKIP-NEXT
; ---------------
; Memory location
; ---------------
; This routine, when supplied with a base address in HL and an index in A
; will calculate the address of the A'th entry, where each entry occupies
; five bytes. It is used for reading the semi-tone table and addressing
; floating-point numbers in the calculator's memory area.
;; LOC-MEM
L3406: LD C,A ; store the original number $00-$1F.
RLCA ; double.
RLCA ; quadruple.
ADD A,C ; now add original to multiply by five.
LD C,A ; place the result in C.
LD B,$00 ; set B to 0.
ADD HL,BC ; add to form address of start of number in HL.
RET ; return.
; ------------------------------
; Get from memory area ($E0 etc.)
; ------------------------------
; Literals $E0 to $FF
; A holds $00-$1F offset.
; The calculator stack increases by 5 bytes.
;; get-mem-xx
L340F: PUSH DE ; save STKEND
LD HL,($5C68) ; MEM is base address of the memory cells.
CALL L3406 ; routine LOC-MEM so that HL = first byte
CALL L33C0 ; routine MOVE-FP moves 5 bytes with memory
; check.
; DE now points to new STKEND.
POP HL ; original STKEND is now RESULT pointer.
RET ; return.
; --------------------------
; Stack a constant (A0 etc.)
; --------------------------
; This routine allows a one-byte instruction to stack up to 32 constants
; held in short form in a table of constants. In fact only 5 constants are
; required. On entry the A register holds the literal ANDed with 1F.
; It isn't very efficient and it would have been better to hold the
; numbers in full, five byte form and stack them in a similar manner
; to that used for semi-tone table values.
;; stk-const-xx
L341B: LD H,D ; save STKEND - required for result
LD L,E ;
EXX ; swap
PUSH HL ; save pointer to next literal
LD HL,L32C5 ; Address: stk-zero - start of table of
; constants
EXX ;
CALL L33F7 ; routine SKIP-CONS
CALL L33C8 ; routine STK-CONST
EXX ;
POP HL ; restore pointer to next literal.
EXX ;
RET ; return.
; --------------------------------
; Store in a memory area ($C0 etc.)
; --------------------------------
; Offsets $C0 to $DF
; Although 32 memory storage locations can be addressed, only six
; $C0 to $C5 are required by the ROM and only the thirty bytes (6*5)
; required for these are allocated. Spectrum programmers who wish to
; use the floating point routines from assembly language may wish to
; alter the system variable MEM to point to 160 bytes of RAM to have
; use the full range available.
; A holds the derived offset $00-$1F.
; This is a unary operation, so on entry HL points to the last value and DE
; points to STKEND.
;; st-mem-xx
L342D: PUSH HL ; save the result pointer.
EX DE,HL ; transfer to DE.
LD HL,($5C68) ; fetch MEM the base of memory area.
CALL L3406 ; routine LOC-MEM sets HL to the destination.
EX DE,HL ; swap - HL is start, DE is destination.
CALL L33C0 ; routine MOVE-FP.
; note. a short ld bc,5; ldir
; the embedded memory check is not required
; so these instructions would be faster.
EX DE,HL ; DE = STKEND
POP HL ; restore original result pointer
RET ; return.
; ------------------------------------
; Swap first number with second number
; ------------------------------------
; This routine exchanges the last two values on the calculator stack
; On entry, as always with binary operations,
; HL=first number, DE=second number
; On exit, HL=result, DE=stkend.
;; exchange
L343C: LD B,$05 ; there are five bytes to be swapped
; start of loop.
;; SWAP-BYTE
L343E: LD A,(DE) ; each byte of second
LD C,(HL) ; each byte of first
EX DE,HL ; swap pointers
LD (DE),A ; store each byte of first
LD (HL),C ; store each byte of second
INC HL ; advance both
INC DE ; pointers.
DJNZ L343E ; loop back to SWAP-BYTE until all 5 done.
EX DE,HL ; even up the exchanges
; so that DE addresses STKEND.
RET ; return.
; --------------------------
; Series generator (86 etc.)
; --------------------------
; The Spectrum uses Chebyshev polynomials to generate approximations for
; SIN, ATN, LN and EXP. These are named after the Russian mathematician
; Pafnuty Chebyshev, born in 1821, who did much pioneering work on numerical
; series. As far as calculators are concerned, Chebyshev polynomials have an
; advantage over other series, for example the Taylor series, as they can
; reach an approximation in just six iterations for SIN, eight for EXP and
; twelve for LN and ATN. The mechanics of the routine are interesting but
; for full treatment of how these are generated with demonstrations in
; Sinclair BASIC see "The Complete Spectrum ROM Disassembly" by Dr Ian Logan
; and Dr Frank O'Hara, published 1983 by Melbourne House.
;; series-xx
L3449: LD B,A ; parameter $00 - $1F to B counter
CALL L335E ; routine GEN-ENT-1 is called.
; A recursive call to a special entry point
; in the calculator that puts the B register
; in the system variable BREG. The return
; address is the next location and where
; the calculator will expect its first
; instruction - now pointed to by HL'.
; The previous pointer to the series of
; five-byte numbers goes on the machine stack.
; The initialization phase.
DB $31 ;;duplicate x,x
DB $0F ;;addition x+x
DB $C0 ;;st-mem-0 x+x
DB $02 ;;delete .
DB $A0 ;;stk-zero 0
DB $C2 ;;st-mem-2 0
; a loop is now entered to perform the algebraic calculation for each of
; the numbers in the series
;; G-LOOP
L3453: DB $31 ;;duplicate v,v.
DB $E0 ;;get-mem-0 v,v,x+2
DB $04 ;;multiply v,v*x+2
DB $E2 ;;get-mem-2 v,v*x+2,v
DB $C1 ;;st-mem-1
DB $03 ;;subtract
DB $38 ;;end-calc
; the previous pointer is fetched from the machine stack to H'L' where it
; addresses one of the numbers of the series following the series literal.
CALL L33C6 ; routine STK-DATA is called directly to
; push a value and advance H'L'.
CALL L3362 ; routine GEN-ENT-2 recursively re-enters
; the calculator without disturbing
; system variable BREG
; H'L' value goes on the machine stack and is
; then loaded as usual with the next address.
DB $0F ;;addition
DB $01 ;;exchange
DB $C2 ;;st-mem-2
DB $02 ;;delete
DB $35 ;;dec-jr-nz
DB $EE ;;back to L3453, G-LOOP
; when the counted loop is complete the final subtraction yields the result
; for example SIN X.
DB $E1 ;;get-mem-1
DB $03 ;;subtract
DB $38 ;;end-calc
RET ; return with H'L' pointing to location
; after last number in series.
; -----------------------
; Absolute magnitude (2A)
; -----------------------
; This calculator literal finds the absolute value of the last value,
; integer or floating point, on calculator stack.
;; abs
L346A: LD B,$FF ; signal abs
JR L3474 ; forward to NEG-TEST
; -----------------------
; Handle unary minus (1B)
; -----------------------
; Unary so on entry HL points to last value, DE to STKEND.
;; NEGATE
;; negate
L346E: CALL L34E9 ; call routine TEST-ZERO and
RET C ; return if so leaving zero unchanged.
LD B,$00 ; signal negate required before joining
; common code.
;; NEG-TEST
L3474: LD A,(HL) ; load first byte and
AND A ; test for zero
JR Z,L3483 ; forward to INT-CASE if a small integer
; for floating point numbers a single bit denotes the sign.
INC HL ; address the first byte of mantissa.
LD A,B ; action flag $FF=abs, $00=neg.
AND $80 ; now $80 $00
OR (HL) ; sets bit 7 for abs
RLA ; sets carry for abs and if number negative
CCF ; complement carry flag
RRA ; and rotate back in altering sign
LD (HL),A ; put the altered adjusted number back
DEC HL ; HL points to result
RET ; return with DE unchanged
; ---
; for integer numbers an entire byte denotes the sign.
;; INT-CASE
L3483: PUSH DE ; save STKEND.
PUSH HL ; save pointer to the last value/result.
CALL L2D7F ; routine INT-FETCH puts integer in DE
; and the sign in C.
POP HL ; restore the result pointer.
LD A,B ; $FF=abs, $00=neg
OR C ; $FF for abs, no change neg
CPL ; $00 for abs, switched for neg
LD C,A ; transfer result to sign byte.
CALL L2D8E ; routine INT-STORE to re-write the integer.
POP DE ; restore STKEND.
RET ; return.
; -----------
; Signum (29)
; -----------
; This routine replaces the last value on the calculator stack,
; which may be in floating point or integer form, with the integer values
; zero if zero, with one if positive and with -minus one if negative.
;; sgn
L3492: CALL L34E9 ; call routine TEST-ZERO and
RET C ; exit if so as no change is required.
PUSH DE ; save pointer to STKEND.
LD DE,$0001 ; the result will be 1.
INC HL ; skip over the exponent.
RL (HL) ; rotate the sign bit into the carry flag.
DEC HL ; step back to point to the result.
SBC A,A ; byte will be $FF if negative, $00 if positive.
LD C,A ; store the sign byte in the C register.
CALL L2D8E ; routine INT-STORE to overwrite the last
; value with 0001 and sign.
POP DE ; restore STKEND.
RET ; return.
; -----------------------
; Handle IN function (2C)
; -----------------------
; This function reads a byte from an input port.
;; in
L34A5: CALL L1E99 ; routine FIND-INT2 puts port address in BC.
; all 16 bits are put on the address line.
IN A,(C) ; read the port.
JR L34B0 ; exit to STACK-A (via IN-PK-STK to save a byte
; of instruction code).
; -------------------------
; Handle PEEK function (2B)
; -------------------------
; This function returns the contents of a memory address.
; The entire address space can be peeked including the ROM.
;; peek
L34AC: CALL L1E99 ; routine FIND-INT2 puts address in BC.
LD A,(BC) ; load contents into A register.
;; IN-PK-STK
L34B0: JP L2D28 ; exit via STACK-A to put value on the
; calculator stack.
; ---------------
; USR number (2D)
; ---------------
; The USR function followed by a number 0-65535 is the method by which
; the Spectrum invokes machine code programs. This function returns the
; contents of the BC register pair.
; Note. that STACK-BC re-initializes the IY register if a user-written
; program has altered it.
;; usr-no
L34B3: CALL L1E99 ; routine FIND-INT2 to fetch the
; supplied address into BC.
LD HL,L2D2B ; address: STACK-BC is
PUSH HL ; pushed onto the machine stack.
PUSH BC ; then the address of the machine code
; routine.
RET ; make an indirect jump to the routine
; and, hopefully, to STACK-BC also.
; ---------------
; USR string (19)
; ---------------
; The user function with a one-character string argument, calculates the
; address of the User Defined Graphic character that is in the string.
; As an alternative, the ASCII equivalent, upper or lower case,
; may be supplied. This provides a user-friendly method of redefining
; the 21 User Definable Graphics e.g.
; POKE USR "a", BIN 10000000 will put a dot in the top left corner of the
; character 144.
; Note. the curious double check on the range. With 26 UDGs the first check
; only is necessary. With anything less the second check only is required.
; It is highly likely that the first check was written by Steven Vickers.
;; usr-$
L34BC: CALL L2BF1 ; routine STK-FETCH fetches the string
; parameters.
DEC BC ; decrease BC by
LD A,B ; one to test
OR C ; the length.
JR NZ,L34E7 ; to REPORT-A if not a single character.
LD A,(DE) ; fetch the character
CALL L2C8D ; routine ALPHA sets carry if 'A-Z' or 'a-z'.
JR C,L34D3 ; forward to USR-RANGE if ASCII.
SUB $90 ; make udgs range 0-20d
JR C,L34E7 ; to REPORT-A if too low. e.g. usr " ".
CP $15 ; Note. this test is not necessary.
JR NC,L34E7 ; to REPORT-A if higher than 20.
INC A ; make range 1-21d to match LSBs of ASCII
;; USR-RANGE
L34D3: DEC A ; make range of bits 0-4 start at zero
ADD A,A ; multiply by eight
ADD A,A ; and lose any set bits
ADD A,A ; range now 0 - 25*8
CP $A8 ; compare to 21*8
JR NC,L34E7 ; to REPORT-A if originally higher
; than 'U','u' or graphics U.
LD BC,($5C7B) ; fetch the UDG system variable value.
ADD A,C ; add the offset to character
LD C,A ; and store back in register C.
JR NC,L34E4 ; forward to USR-STACK if no overflow.
INC B ; increment high byte.
;; USR-STACK
L34E4: JP L2D2B ; jump back and exit via STACK-BC to store
; ---
;; REPORT-A
L34E7: RST 08H ; ERROR-1
DB $09 ; Error Report: Invalid argument
; -------------
; Test for zero
; -------------
; Test if top value on calculator stack is zero.
; The carry flag is set if the last value is zero but no registers are altered.
; All five bytes will be zero but first four only need be tested.
; On entry HL points to the exponent the first byte of the value.
;; TEST-ZERO
L34E9: PUSH HL ; preserve HL which is used to address.
PUSH BC ; preserve BC which is used as a store.
LD B,A ; preserve A in B.
LD A,(HL) ; load first byte to accumulator
INC HL ; advance.
OR (HL) ; OR with second byte and clear carry.
INC HL ; advance.
OR (HL) ; OR with third byte.
INC HL ; advance.
OR (HL) ; OR with fourth byte.
LD A,B ; restore A without affecting flags.
POP BC ; restore the saved
POP HL ; registers.
RET NZ ; return if not zero and with carry reset.
SCF ; set the carry flag.
RET ; return with carry set if zero.
; -----------------------
; Greater than zero ($37)
; -----------------------
; Test if the last value on the calculator stack is greater than zero.
; This routine is also called directly from the end-tests of the comparison
; routine.
;; GREATER-0
;; greater-0
L34F9: CALL L34E9 ; routine TEST-ZERO
RET C ; return if was zero as this
; is also the Boolean 'false' value.
LD A,$FF ; prepare XOR mask for sign bit
JR L3507 ; forward to SIGN-TO-C
; to put sign in carry
; (carry will become set if sign is positive)
; and then overwrite location with 1 or 0
; as appropriate.
; ------------------------
; Handle NOT operator ($30)
; ------------------------
; This overwrites the last value with 1 if it was zero else with zero
; if it was any other value.
;
; e.g NOT 0 returns 1, NOT 1 returns 0, NOT -3 returns 0.
;
; The subroutine is also called directly from the end-tests of the comparison
; operator.
;; NOT
;; not
L3501: CALL L34E9 ; routine TEST-ZERO sets carry if zero
JR L350B ; to FP-0/1 to overwrite operand with
; 1 if carry is set else to overwrite with zero.
; -------------------
; Less than zero (36)
; -------------------
; Destructively test if last value on calculator stack is less than zero.
; Bit 7 of second byte will be set if so.
;; less-0
L3506: XOR A ; set xor mask to zero
; (carry will become set if sign is negative).
; transfer sign of mantissa to Carry Flag.
;; SIGN-TO-C
L3507: INC HL ; address 2nd byte.
XOR (HL) ; bit 7 of HL will be set if number is negative.
DEC HL ; address 1st byte again.
RLCA ; rotate bit 7 of A to carry.
; -----------
; Zero or one
; -----------
; This routine places an integer value of zero or one at the addressed location
; of the calculator stack or MEM area. The value one is written if carry is
; set on entry else zero.
;; FP-0/1
L350B: PUSH HL ; save pointer to the first byte
LD A,$00 ; load accumulator with zero - without
; disturbing flags.
LD (HL),A ; zero to first byte
INC HL ; address next
LD (HL),A ; zero to 2nd byte
INC HL ; address low byte of integer
RLA ; carry to bit 0 of A
LD (HL),A ; load one or zero to low byte.
RRA ; restore zero to accumulator.
INC HL ; address high byte of integer.
LD (HL),A ; put a zero there.
INC HL ; address fifth byte.
LD (HL),A ; put a zero there.
POP HL ; restore pointer to the first byte.
RET ; return.
; -----------------------
; Handle OR operator (07)
; -----------------------
; The Boolean OR operator. eg. X OR Y
; The result is zero if both values are zero else a non-zero value.
;
; e.g. 0 OR 0 returns 0.
; -3 OR 0 returns -3.
; 0 OR -3 returns 1.
; -3 OR 2 returns 1.
;
; A binary operation.
; On entry HL points to first operand (X) and DE to second operand (Y).
;; or
L351B: EX DE,HL ; make HL point to second number
CALL L34E9 ; routine TEST-ZERO
EX DE,HL ; restore pointers
RET C ; return if result was zero - first operand,
; now the last value, is the result.
SCF ; set carry flag
JR L350B ; back to FP-0/1 to overwrite the first operand
; with the value 1.
; -----------------------------
; Handle number AND number (08)
; -----------------------------
; The Boolean AND operator.
;
; e.g. -3 AND 2 returns -3.
; -3 AND 0 returns 0.
; 0 and -2 returns 0.
; 0 and 0 returns 0.
;
; Compare with OR routine above.
;; no-&-no
L3524: EX DE,HL ; make HL address second operand.
CALL L34E9 ; routine TEST-ZERO sets carry if zero.
EX DE,HL ; restore pointers.
RET NC ; return if second non-zero, first is result.
;
AND A ; else clear carry.
JR L350B ; back to FP-0/1 to overwrite first operand
; with zero for return value.
; -----------------------------
; Handle string AND number (10)
; -----------------------------
; e.g. "You Win" AND score>99 will return the string if condition is true
; or the null string if false.
;; str-&-no
L352D: EX DE,HL ; make HL point to the number.
CALL L34E9 ; routine TEST-ZERO.
EX DE,HL ; restore pointers.
RET NC ; return if number was not zero - the string
; is the result.
; if the number was zero (false) then the null string must be returned by
; altering the length of the string on the calculator stack to zero.
PUSH DE ; save pointer to the now obsolete number
; (which will become the new STKEND)
DEC DE ; point to the 5th byte of string descriptor.
XOR A ; clear the accumulator.
LD (DE),A ; place zero in high byte of length.
DEC DE ; address low byte of length.
LD (DE),A ; place zero there - now the null string.
POP DE ; restore pointer - new STKEND.
RET ; return.
; -----------------------------------
; Perform comparison ($09-$0E, $11-$16)
; -----------------------------------
; True binary operations.
;
; A single entry point is used to evaluate six numeric and six string
; comparisons. On entry, the calculator literal is in the B register and
; the two numeric values, or the two string parameters, are on the
; calculator stack.
; The individual bits of the literal are manipulated to group similar
; operations although the SUB 8 instruction does nothing useful and merely
; alters the string test bit.
; Numbers are compared by subtracting one from the other, strings are
; compared by comparing every character until a mismatch, or the end of one
; or both, is reached.
;
; Numeric Comparisons.
; --------------------
; The 'x>y' example is the easiest as it employs straight-thru logic.
; Number y is subtracted from x and the result tested for greater-0 yielding
; a final value 1 (true) or 0 (false).
; For 'x<y' the same logic is used but the two values are first swapped on the
; calculator stack.
; For 'x=y' NOT is applied to the subtraction result yielding true if the
; difference was zero and false with anything else.
; The first three numeric comparisons are just the opposite of the last three
; so the same processing steps are used and then a final NOT is applied.
;
; literal Test No sub 8 ExOrNot 1st RRCA exch sub ? End-Tests
; ========= ==== == ======== === ======== ======== ==== === = === === ===
; no-l-eql x<=y 09 00000001 dec 00000000 00000000 ---- x-y ? --- >0? NOT
; no-gr-eql x>=y 0A 00000010 dec 00000001 10000000c swap y-x ? --- >0? NOT
; nos-neql x<>y 0B 00000011 dec 00000010 00000001 ---- x-y ? NOT --- NOT
; no-grtr x>y 0C 00000100 - 00000100 00000010 ---- x-y ? --- >0? ---
; no-less x<y 0D 00000101 - 00000101 10000010c swap y-x ? --- >0? ---
; nos-eql x=y 0E 00000110 - 00000110 00000011 ---- x-y ? NOT --- ---
;
; comp -> C/F
; ==== ===
; str-l-eql x$<=y$ 11 00001001 dec 00001000 00000100 ---- x$y$ 0 !or >0? NOT
; str-gr-eql x$>=y$ 12 00001010 dec 00001001 10000100c swap y$x$ 0 !or >0? NOT
; strs-neql x$<>y$ 13 00001011 dec 00001010 00000101 ---- x$y$ 0 !or >0? NOT
; str-grtr x$>y$ 14 00001100 - 00001100 00000110 ---- x$y$ 0 !or >0? ---
; str-less x$<y$ 15 00001101 - 00001101 10000110c swap y$x$ 0 !or >0? ---
; strs-eql x$=y$ 16 00001110 - 00001110 00000111 ---- x$y$ 0 !or >0? ---
;
; String comparisons are a little different in that the eql/neql carry flag
; from the 2nd RRCA is, as before, fed into the first of the end tests but
; along the way it gets modified by the comparison process. The result on the
; stack always starts off as zero and the carry fed in determines if NOT is
; applied to it. So the only time the greater-0 test is applied is if the
; stack holds zero which is not very efficient as the test will always yield
; zero. The most likely explanation is that there were once separate end tests
; for numbers and strings.
;; no-l-eql, etc.
L353B: LD A,B ; transfer literal to accumulator.
SUB $08 ; subtract eight - which is not useful.
BIT 2,A ; isolate '>', '<', '='.
JR NZ,L3543 ; skip to EX-OR-NOT with these.
DEC A ; else make $00-$02, $08-$0A to match bits 0-2.
;; EX-OR-NOT
L3543: RRCA ; the first RRCA sets carry for a swap.
JR NC,L354E ; forward to NU-OR-STR with other 8 cases
; for the other 4 cases the two values on the calculator stack are exchanged.
PUSH AF ; save A and carry.
PUSH HL ; save HL - pointer to first operand.
; (DE points to second operand).
CALL L343C ; routine exchange swaps the two values.
; (HL = second operand, DE = STKEND)
POP DE ; DE = first operand
EX DE,HL ; as we were.
POP AF ; restore A and carry.
; Note. it would be better if the 2nd RRCA preceded the string test.
; It would save two duplicate bytes and if we also got rid of that sub 8
; at the beginning we wouldn't have to alter which bit we test.
;; NU-OR-STR
L354E: BIT 2,A ; test if a string comparison.
JR NZ,L3559 ; forward to STRINGS if so.
; continue with numeric comparisons.
RRCA ; 2nd RRCA causes eql/neql to set carry.
PUSH AF ; save A and carry
CALL L300F ; routine subtract leaves result on stack.
JR L358C ; forward to END-TESTS
; ---
;; STRINGS
L3559: RRCA ; 2nd RRCA causes eql/neql to set carry.
PUSH AF ; save A and carry.
CALL L2BF1 ; routine STK-FETCH gets 2nd string params
PUSH DE ; save start2 *.
PUSH BC ; and the length.
CALL L2BF1 ; routine STK-FETCH gets 1st string
; parameters - start in DE, length in BC.
POP HL ; restore length of second to HL.
; A loop is now entered to compare, by subtraction, each corresponding character
; of the strings. For each successful match, the pointers are incremented and
; the lengths decreased and the branch taken back to here. If both string
; remainders become null at the same time, then an exact match exists.
;; BYTE-COMP
L3564: LD A,H ; test if the second string
OR L ; is the null string and hold flags.
EX (SP),HL ; put length2 on stack, bring start2 to HL *.
LD A,B ; hi byte of length1 to A
JR NZ,L3575 ; forward to SEC-PLUS if second not null.
OR C ; test length of first string.
;; SECND-LOW
L356B: POP BC ; pop the second length off stack.
JR Z,L3572 ; forward to BOTH-NULL if first string is also
; of zero length.
; the true condition - first is longer than second (SECND-LESS)
POP AF ; restore carry (set if eql/neql)
CCF ; complement carry flag.
; Note. equality becomes false.
; Inequality is true. By swapping or applying
; a terminal 'not', all comparisons have been
; manipulated so that this is success path.
JR L3588 ; forward to leave via STR-TEST
; ---
; the branch was here with a match
;; BOTH-NULL
L3572: POP AF ; restore carry - set for eql/neql
JR L3588 ; forward to STR-TEST
; ---
; the branch was here when 2nd string not null and low byte of first is yet
; to be tested.
;; SEC-PLUS
L3575: OR C ; test the length of first string.
JR Z,L3585 ; forward to FRST-LESS if length is zero.
; both strings have at least one character left.
LD A,(DE) ; fetch character of first string.
SUB (HL) ; subtract with that of 2nd string.
JR C,L3585 ; forward to FRST-LESS if carry set
JR NZ,L356B ; back to SECND-LOW and then STR-TEST
; if not exact match.
DEC BC ; decrease length of 1st string.
INC DE ; increment 1st string pointer.
INC HL ; increment 2nd string pointer.
EX (SP),HL ; swap with length on stack
DEC HL ; decrement 2nd string length
JR L3564 ; back to BYTE-COMP
; ---
; the false condition.
;; FRST-LESS
L3585: POP BC ; discard length
POP AF ; pop A
AND A ; clear the carry for false result.
; ---
; exact match and x$>y$ rejoin here
;; STR-TEST
L3588: PUSH AF ; save A and carry
RST 28H ;; FP-CALC
DB $A0 ;;stk-zero an initial false value.
DB $38 ;;end-calc
; both numeric and string paths converge here.
;; END-TESTS
L358C: POP AF ; pop carry - will be set if eql/neql
PUSH AF ; save it again.
CALL C,L3501 ; routine NOT sets true(1) if equal(0)
; or, for strings, applies true result.
POP AF ; pop carry and
PUSH AF ; save A
CALL NC,L34F9 ; routine GREATER-0 tests numeric subtraction
; result but also needlessly tests the string
; value for zero - it must be.
POP AF ; pop A
RRCA ; the third RRCA - test for '<=', '>=' or '<>'.
CALL NC,L3501 ; apply a terminal NOT if so.
RET ; return.
; -------------------------
; String concatenation ($17)
; -------------------------
; This literal combines two strings into one e.g. LET a$ = b$ + c$
; The two parameters of the two strings to be combined are on the stack.
;; strs-add
L359C: CALL L2BF1 ; routine STK-FETCH fetches string parameters
; and deletes calculator stack entry.
PUSH DE ; save start address.
PUSH BC ; and length.
CALL L2BF1 ; routine STK-FETCH for first string
POP HL ; re-fetch first length
PUSH HL ; and save again
PUSH DE ; save start of second string
PUSH BC ; and its length.
ADD HL,BC ; add the two lengths.
LD B,H ; transfer to BC
LD C,L ; and create
RST 30H ; BC-SPACES in workspace.
; DE points to start of space.
CALL L2AB2 ; routine STK-STO-$ stores parameters
; of new string updating STKEND.
POP BC ; length of first
POP HL ; address of start
LD A,B ; test for
OR C ; zero length.
JR Z,L35B7 ; to OTHER-STR if null string
LDIR ; copy string to workspace.
;; OTHER-STR
L35B7: POP BC ; now second length
POP HL ; and start of string
LD A,B ; test this one
OR C ; for zero length
JR Z,L35BF ; skip forward to STK-PNTRS if so as complete.
LDIR ; else copy the bytes.
; and continue into next routine which
; sets the calculator stack pointers.
; --------------------
; Check stack pointers
; --------------------
; Register DE is set to STKEND and HL, the result pointer, is set to five
; locations below this.
; This routine is used when it is inconvenient to save these values at the
; time the calculator stack is manipulated due to other activity on the
; machine stack.
; This routine is also used to terminate the VAL and READ-IN routines for
; the same reason and to initialize the calculator stack at the start of
; the CALCULATE routine.
;; STK-PNTRS
L35BF: LD HL,($5C65) ; fetch STKEND value from system variable.
LD DE,$FFFB ; the value -5
PUSH HL ; push STKEND value.
ADD HL,DE ; subtract 5 from HL.
POP DE ; pop STKEND to DE.
RET ; return.
; ----------------
; Handle CHR$ (2F)
; ----------------
; This function returns a single character string that is a result of
; converting a number in the range 0-255 to a string e.g. CHR$ 65 = "A".
;; chrs
L35C9: CALL L2DD5 ; routine FP-TO-A puts the number in A.
JR C,L35DC ; forward to REPORT-Bd if overflow
JR NZ,L35DC ; forward to REPORT-Bd if negative
PUSH AF ; save the argument.
LD BC,$0001 ; one space required.
RST 30H ; BC-SPACES makes DE point to start
POP AF ; restore the number.
LD (DE),A ; and store in workspace
CALL L2AB2 ; routine STK-STO-$ stacks descriptor.
EX DE,HL ; make HL point to result and DE to STKEND.
RET ; return.
; ---
;; REPORT-Bd
L35DC: RST 08H ; ERROR-1
DB $0A ; Error Report: Integer out of range
; ----------------------------
; Handle VAL and VAL$ ($1D, $18)
; ----------------------------
; VAL treats the characters in a string as a numeric expression.
; e.g. VAL "2.3" = 2.3, VAL "2+4" = 6, VAL ("2" + "4") = 24.
; VAL$ treats the characters in a string as a string expression.
; e.g. VAL$ (z$+"(2)") = a$(2) if z$ happens to be "a$".
;; val
;; val$
L35DE: LD HL,($5C5D) ; fetch value of system variable CH_ADD
PUSH HL ; and save on the machine stack.
LD A,B ; fetch the literal (either $1D or $18).
ADD A,$E3 ; add $E3 to form $00 (setting carry) or $FB.
SBC A,A ; now form $FF bit 6 = numeric result
; or $00 bit 6 = string result.
PUSH AF ; save this mask on the stack
CALL L2BF1 ; routine STK-FETCH fetches the string operand
; from calculator stack.
PUSH DE ; save the address of the start of the string.
INC BC ; increment the length for a carriage return.
RST 30H ; BC-SPACES creates the space in workspace.
POP HL ; restore start of string to HL.
LD ($5C5D),DE ; load CH_ADD with start DE in workspace.
PUSH DE ; save the start in workspace
LDIR ; copy string from program or variables or
; workspace to the workspace area.
EX DE,HL ; end of string + 1 to HL
DEC HL ; decrement HL to point to end of new area.
LD (HL),$0D ; insert a carriage return at end.
RES 7,(IY+$01) ; update FLAGS - signal checking syntax.
CALL L24FB ; routine SCANNING evaluates string
; expression and result.
RST 18H ; GET-CHAR fetches next character.
CP $0D ; is it the expected carriage return ?
JR NZ,L360C ; forward to V-RPORT-C if not
; 'Nonsense in BASIC'.
POP HL ; restore start of string in workspace.
POP AF ; restore expected result flag (bit 6).
XOR (IY+$01) ; xor with FLAGS now updated by SCANNING.
AND $40 ; test bit 6 - should be zero if result types
; match.
;; V-RPORT-C
L360C: JP NZ,L1C8A ; jump back to REPORT-C with a result mismatch.
LD ($5C5D),HL ; set CH_ADD to the start of the string again.
SET 7,(IY+$01) ; update FLAGS - signal running program.
CALL L24FB ; routine SCANNING evaluates the string
; in full leaving result on calculator stack.
POP HL ; restore saved character address in program.
LD ($5C5D),HL ; and reset the system variable CH_ADD.
JR L35BF ; back to exit via STK-PNTRS.
; resetting the calculator stack pointers
; HL and DE from STKEND as it wasn't possible
; to preserve them during this routine.
; ----------------
; Handle STR$ (2E)
; ----------------
;
;
;; str$
L361F: LD BC,$0001 ; create an initial byte in workspace
RST 30H ; using BC-SPACES restart.
LD ($5C5B),HL ; set system variable K_CUR to new location.
PUSH HL ; and save start on machine stack also.
LD HL,($5C51) ; fetch value of system variable CURCHL
PUSH HL ; and save that too.
LD A,$FF ; select system channel 'R'.
CALL L1601 ; routine CHAN-OPEN opens it.
CALL L2DE3 ; routine PRINT-FP outputs the number to
; workspace updating K-CUR.
POP HL ; restore current channel.
CALL L1615 ; routine CHAN-FLAG resets flags.
POP DE ; fetch saved start of string to DE.
LD HL,($5C5B) ; load HL with end of string from K_CUR.
AND A ; prepare for true subtraction.
SBC HL,DE ; subtract start from end to give length.
LD B,H ; transfer the length to
LD C,L ; the BC register pair.
CALL L2AB2 ; routine STK-STO-$ stores string parameters
; on the calculator stack.
EX DE,HL ; HL = last value, DE = STKEND.
RET ; return.
; ------------
; Read-in (1A)
; ------------
; This is the calculator literal used by the INKEY$ function when a '#'
; is encountered after the keyword.
; INKEY$ # does not interact correctly with the keyboard, #0 or #1, and
; its uses are for other channels.
;; read-in
L3645: CALL L1E94 ; routine FIND-INT1 fetches stream to A
CP $10 ; compare with 16 decimal.
JP NC,L1E9F ; jump to REPORT-Bb if not in range 0 - 15.
; 'Integer out of range'
; (REPORT-Bd is within range)
LD HL,($5C51) ; fetch current channel CURCHL
PUSH HL ; save it
CALL L1601 ; routine CHAN-OPEN opens channel
CALL L15E6 ; routine INPUT-AD - the channel must have an
; input stream or else error here from stream
; stub.
LD BC,$0000 ; initialize length of string to zero
JR NC,L365F ; forward to R-I-STORE if no key detected.
INC C ; increase length to one.
RST 30H ; BC-SPACES creates space for one character
; in workspace.
LD (DE),A ; the character is inserted.
;; R-I-STORE
L365F: CALL L2AB2 ; routine STK-STO-$ stacks the string
; parameters.
POP HL ; restore current channel address
CALL L1615 ; routine CHAN-FLAG resets current channel
; system variable and flags.
JP L35BF ; jump back to STK-PNTRS
; ----------------
; Handle CODE (1C)
; ----------------
; Returns the ASCII code of a character or first character of a string
; e.g. CODE "Aardvark" = 65, CODE "" = 0.
;; code
L3669: CALL L2BF1 ; routine STK-FETCH to fetch and delete the
; string parameters.
; DE points to the start, BC holds the length.
LD A,B ; test length
OR C ; of the string.
JR Z,L3671 ; skip to STK-CODE with zero if the null string.
LD A,(DE) ; else fetch the first character.
;; STK-CODE
L3671: JP L2D28 ; jump back to STACK-A (with memory check)
; ---------------
; Handle LEN (1E)
; ---------------
; Returns the length of a string.
; In Sinclair BASIC strings can be more than twenty thousand characters long
; so a sixteen-bit register is required to store the length
;; len
L3674: CALL L2BF1 ; routine STK-FETCH to fetch and delete the
; string parameters from the calculator stack.
; register BC now holds the length of string.
JP L2D2B ; jump back to STACK-BC to save result on the
; calculator stack (with memory check).
; -------------------------
; Decrease the counter (35)
; -------------------------
; The calculator has an instruction that decrements a single-byte
; pseudo-register and makes consequential relative jumps just like
; the Z80's DJNZ instruction.
;; dec-jr-nz
L367A: EXX ; switch in set that addresses code
PUSH HL ; save pointer to offset byte
LD HL,$5C67 ; address BREG in system variables
DEC (HL) ; decrement it
POP HL ; restore pointer
JR NZ,L3687 ; to JUMP-2 if not zero
INC HL ; step past the jump length.
EXX ; switch in the main set.
RET ; return.
; Note. as a general rule the calculator avoids using the IY register
; otherwise the cumbersome 4 instructions in the middle could be replaced by
; dec (iy+$2d) - three bytes instead of six.
; ---------
; Jump (33)
; ---------
; This enables the calculator to perform relative jumps just like
; the Z80 chip's JR instruction
;; jump
;; JUMP
L3686: EXX ;switch in pointer set
;; JUMP-2
L3687: LD E,(HL) ; the jump byte 0-127 forward, 128-255 back.
LD A,E ; transfer to accumulator.
RLA ; if backward jump, carry is set.
SBC A,A ; will be $FF if backward or $00 if forward.
LD D,A ; transfer to high byte.
ADD HL,DE ; advance calculator pointer forward or back.
EXX ; switch back.
RET ; return.
; -----------------
; Jump on true (00)
; -----------------
; This enables the calculator to perform conditional relative jumps
; dependent on whether the last test gave a true result
;; jump-true
L368F: INC DE ; collect the
INC DE ; third byte
LD A,(DE) ; of the test
DEC DE ; result and
DEC DE ; backtrack.
AND A ; is result 0 or 1 ?
JR NZ,L3686 ; back to JUMP if true (1).
EXX ; else switch in the pointer set.
INC HL ; step past the jump length.
EXX ; switch in the main set.
RET ; return.
; -----------------------
; End of calculation (38)
; -----------------------
; The end-calc literal terminates a mini-program written in the Spectrum's
; internal language.
;; end-calc
L369B: POP AF ; drop the calculator return address RE-ENTRY
EXX ; switch to the other set.
EX (SP),HL ; transfer H'L' to machine stack for the
; return address.
; when exiting recursion then the previous
; pointer is transferred to H'L'.
EXX ; back to main set.
RET ; return.
; ------------------------
; THE 'MODULUS' SUBROUTINE
; ------------------------
; (offset: $32 'n-mod-m')
;
;
;; n-mod-m
L36A0: RST 28H ;; FP-CALC 17, 3.
DB $C0 ;;st-mem-0 17, 3.
DB $02 ;;delete 17.
DB $31 ;;duplicate 17, 17.
DB $E0 ;;get-mem-0 17, 17, 3.
DB $05 ;;division 17, 17/3.
DB $27 ;;int 17, 5.
DB $E0 ;;get-mem-0 17, 5, 3.
DB $01 ;;exchange 17, 3, 5.
DB $C0 ;;st-mem-0 17, 3, 5.
DB $04 ;;multiply 17, 15.
DB $03 ;;subtract 2.
DB $E0 ;;get-mem-0 2, 5.
DB $38 ;;end-calc 2, 5.
RET ; return.
; ------------------
; THE 'INT' FUNCTION
; ------------------
; (offset $27: 'int' )
;
; This function returns the integer of x, which is just the same as truncate
; for positive numbers. The truncate literal truncates negative numbers
; upwards so that -3.4 gives -3 whereas the BASIC INT function has to
; truncate negative numbers down so that INT -3.4 is -4.
; It is best to work through using, say, +-3.4 as examples.
;; int
L36AF: RST 28H ;; FP-CALC x. (= 3.4 or -3.4).
DB $31 ;;duplicate x, x.
DB $36 ;;less-0 x, (1/0)
DB $00 ;;jump-true x, (1/0)
DB $04 ;;to L36B7, X-NEG
DB $3A ;;truncate trunc 3.4 = 3.
DB $38 ;;end-calc 3.
RET ; return with + int x on stack.
; ---
;; X-NEG
L36B7: DB $31 ;;duplicate -3.4, -3.4.
DB $3A ;;truncate -3.4, -3.
DB $C0 ;;st-mem-0 -3.4, -3.
DB $03 ;;subtract -.4
DB $E0 ;;get-mem-0 -.4, -3.
DB $01 ;;exchange -3, -.4.
DB $30 ;;not -3, (0).
DB $00 ;;jump-true -3.
DB $03 ;;to L36C2, EXIT -3.
DB $A1 ;;stk-one -3, 1.
DB $03 ;;subtract -4.
;; EXIT
L36C2: DB $38 ;;end-calc -4.
RET ; return.
; ----------------
; Exponential (26)
; ----------------
;
;
;; EXP
;; exp
L36C4: RST 28H ;; FP-CALC
DB $3D ;;re-stack
DB $34 ;;stk-data
DB $F1 ;;Exponent: $81, Bytes: 4
DB $38,$AA,$3B,$29 ;;
DB $04 ;;multiply
DB $31 ;;duplicate
DB $27 ;;int
DB $C3 ;;st-mem-3
DB $03 ;;subtract
DB $31 ;;duplicate
DB $0F ;;addition
DB $A1 ;;stk-one
DB $03 ;;subtract
DB $88 ;;series-08
DB $13 ;;Exponent: $63, Bytes: 1
DB $36 ;;(+00,+00,+00)
DB $58 ;;Exponent: $68, Bytes: 2
DB $65,$66 ;;(+00,+00)
DB $9D ;;Exponent: $6D, Bytes: 3
DB $78,$65,$40 ;;(+00)
DB $A2 ;;Exponent: $72, Bytes: 3
DB $60,$32,$C9 ;;(+00)
DB $E7 ;;Exponent: $77, Bytes: 4
DB $21,$F7,$AF,$24 ;;
DB $EB ;;Exponent: $7B, Bytes: 4
DB $2F,$B0,$B0,$14 ;;
DB $EE ;;Exponent: $7E, Bytes: 4
DB $7E,$BB,$94,$58 ;;
DB $F1 ;;Exponent: $81, Bytes: 4
DB $3A,$7E,$F8,$CF ;;
DB $E3 ;;get-mem-3
DB $38 ;;end-calc
CALL L2DD5 ; routine FP-TO-A
JR NZ,L3705 ; to N-NEGTV
JR C,L3703 ; to REPORT-6b
ADD A,(HL) ;
JR NC,L370C ; to RESULT-OK
;; REPORT-6b
L3703: RST 08H ; ERROR-1
DB $05 ; Error Report: Number too big
;; N-NEGTV
L3705: JR C,L370E ; to RSLT-ZERO
SUB (HL) ;
JR NC,L370E ; to RSLT-ZERO
NEG ; Negate
;; RESULT-OK
L370C: LD (HL),A ;
RET ; return.
; ---
;; RSLT-ZERO
L370E: RST 28H ;; FP-CALC
DB $02 ;;delete
DB $A0 ;;stk-zero
DB $38 ;;end-calc
RET ; return.
; ----------------------
; Natural logarithm (25)
; ----------------------
;
;
;; ln
L3713: RST 28H ;; FP-CALC
DB $3D ;;re-stack
DB $31 ;;duplicate
DB $37 ;;greater-0
DB $00 ;;jump-true
DB $04 ;;to L371C, VALID
DB $38 ;;end-calc
;; REPORT-Ab
L371A: RST 08H ; ERROR-1
DB $09 ; Error Report: Invalid argument
;; VALID
L371C: DB $A0 ;;stk-zero
DB $02 ;;delete
DB $38 ;;end-calc
LD A,(HL) ;
LD (HL),$80 ;
CALL L2D28 ; routine STACK-A
RST 28H ;; FP-CALC
DB $34 ;;stk-data
DB $38 ;;Exponent: $88, Bytes: 1
DB $00 ;;(+00,+00,+00)
DB $03 ;;subtract
DB $01 ;;exchange
DB $31 ;;duplicate
DB $34 ;;stk-data
DB $F0 ;;Exponent: $80, Bytes: 4
DB $4C,$CC,$CC,$CD ;;
DB $03 ;;subtract
DB $37 ;;greater-0
DB $00 ;;jump-true
DB $08 ;;to L373D, GRE.8
DB $01 ;;exchange
DB $A1 ;;stk-one
DB $03 ;;subtract
DB $01 ;;exchange
DB $38 ;;end-calc
INC (HL) ;
RST 28H ;; FP-CALC
;; GRE.8
L373D: DB $01 ;;exchange
DB $34 ;;stk-data
DB $F0 ;;Exponent: $80, Bytes: 4
DB $31,$72,$17,$F8 ;;
DB $04 ;;multiply
DB $01 ;;exchange
DB $A2 ;;stk-half
DB $03 ;;subtract
DB $A2 ;;stk-half
DB $03 ;;subtract
DB $31 ;;duplicate
DB $34 ;;stk-data
DB $32 ;;Exponent: $82, Bytes: 1
DB $20 ;;(+00,+00,+00)
DB $04 ;;multiply
DB $A2 ;;stk-half
DB $03 ;;subtract
DB $8C ;;series-0C
DB $11 ;;Exponent: $61, Bytes: 1
DB $AC ;;(+00,+00,+00)
DB $14 ;;Exponent: $64, Bytes: 1
DB $09 ;;(+00,+00,+00)
DB $56 ;;Exponent: $66, Bytes: 2
DB $DA,$A5 ;;(+00,+00)
DB $59 ;;Exponent: $69, Bytes: 2
DB $30,$C5 ;;(+00,+00)
DB $5C ;;Exponent: $6C, Bytes: 2
DB $90,$AA ;;(+00,+00)
DB $9E ;;Exponent: $6E, Bytes: 3
DB $70,$6F,$61 ;;(+00)
DB $A1 ;;Exponent: $71, Bytes: 3
DB $CB,$DA,$96 ;;(+00)
DB $A4 ;;Exponent: $74, Bytes: 3
DB $31,$9F,$B4 ;;(+00)
DB $E7 ;;Exponent: $77, Bytes: 4
DB $A0,$FE,$5C,$FC ;;
DB $EA ;;Exponent: $7A, Bytes: 4
DB $1B,$43,$CA,$36 ;;
DB $ED ;;Exponent: $7D, Bytes: 4
DB $A7,$9C,$7E,$5E ;;
DB $F0 ;;Exponent: $80, Bytes: 4
DB $6E,$23,$80,$93 ;;
DB $04 ;;multiply
DB $0F ;;addition
DB $38 ;;end-calc
RET ; return.
; -----------------------------
; THE 'TRIGONOMETRIC' FUNCTIONS
; -----------------------------
; Trigonometry is rocket science. It is also used by carpenters and pyramid
; builders.
; Some uses can be quite abstract but the principles can be seen in simple
; right-angled triangles. Triangles have some special properties -
;
; 1) The sum of the three angles is always PI radians (180 degrees).
; Very helpful if you know two angles and wish to find the third.
; 2) In any right-angled triangle the sum of the squares of the two shorter
; sides is equal to the square of the longest side opposite the right-angle.
; Very useful if you know the length of two sides and wish to know the
; length of the third side.
; 3) Functions sine, cosine and tangent enable one to calculate the length
; of an unknown side when the length of one other side and an angle is
; known.
; 4) Functions arcsin, arccosine and arctan enable one to calculate an unknown
; angle when the length of two of the sides is known.
;---------------------------------
; THE 'REDUCE ARGUMENT' SUBROUTINE
;---------------------------------
; (offset $39: 'get-argt')
;
; This routine performs two functions on the angle, in radians, that forms
; the argument to the sine and cosine functions.
; First it ensures that the angle 'wraps round'. That if a ship turns through
; an angle of, say, 3*PI radians (540 degrees) then the net effect is to turn
; through an angle of PI radians (180 degrees).
; Secondly it converts the angle in radians to a fraction of a right angle,
; depending within which quadrant the angle lies, with the periodicity
; resembling that of the desired sine value.
; The result lies in the range -1 to +1.
;
; 90 deg.
;
; (pi/2)
; II +1 I
; |
; sin+ |\ | /| sin+
; cos- | \ | / | cos+
; tan- | \ | / | tan+
; | \|/) |
; 180 deg. (pi) 0 -|----+----|-- 0 (0) 0 degrees
; | /|\ |
; sin- | / | \ | sin-
; cos- | / | \ | cos+
; tan+ |/ | \| tan-
; |
; III -1 IV
; (3pi/2)
;
; 270 deg.
;
;; get-argt
L3783: RST 28H ;; FP-CALC X.
DB $3D ;;re-stack
DB $34 ;;stk-data
DB $EE ;;Exponent: $7E,
;;Bytes: 4
DB $22,$F9,$83,$6E ;; X, 1/(2*PI)
DB $04 ;;multiply X/(2*PI) = fraction
DB $31 ;;duplicate
DB $A2 ;;stk-half
DB $0F ;;addition
DB $27 ;;int
DB $03 ;;subtract now range -.5 to .5
DB $31 ;;duplicate
DB $0F ;;addition now range -1 to 1.
DB $31 ;;duplicate
DB $0F ;;addition now range -2 to +2.
; quadrant I (0 to +1) and quadrant IV (-1 to 0) are now correct.
; quadrant II ranges +1 to +2.
; quadrant III ranges -2 to -1.
DB $31 ;;duplicate Y, Y.
DB $2A ;;abs Y, abs(Y). range 1 to 2
DB $A1 ;;stk-one Y, abs(Y), 1.
DB $03 ;;subtract Y, abs(Y)-1. range 0 to 1
DB $31 ;;duplicate Y, Z, Z.
DB $37 ;;greater-0 Y, Z, (1/0).
DB $C0 ;;st-mem-0 store as possible sign
;; for cosine function.
DB $00 ;;jump-true
DB $04 ;;to L37A1, ZPLUS with quadrants II and III.
; else the angle lies in quadrant I or IV and value Y is already correct.
DB $02 ;;delete Y. delete the test value.
DB $38 ;;end-calc Y.
RET ; return. with Q1 and Q4 >>>
; ---
; the branch was here with quadrants II (0 to 1) and III (1 to 0).
; Y will hold -2 to -1 if this is quadrant III.
;; ZPLUS
L37A1: DB $A1 ;;stk-one Y, Z, 1.
DB $03 ;;subtract Y, Z-1. Q3 = 0 to -1
DB $01 ;;exchange Z-1, Y.
DB $36 ;;less-0 Z-1, (1/0).
DB $00 ;;jump-true Z-1.
DB $02 ;;to L37A8, YNEG
;;if angle in quadrant III
; else angle is within quadrant II (-1 to 0)
DB $1B ;;negate range +1 to 0.
;; YNEG
L37A8: DB $38 ;;end-calc quadrants II and III correct.
RET ; return.
;----------------------
; THE 'COSINE' FUNCTION
;----------------------
; (offset $20: 'cos')
; Cosines are calculated as the sine of the opposite angle rectifying the
; sign depending on the quadrant rules.
;
;
; /|
; h /y|
; / |o
; /x |
; /----|
; a
;
; The cosine of angle x is the adjacent side (a) divided by the hypotenuse 1.
; However if we examine angle y then a/h is the sine of that angle.
; Since angle x plus angle y equals a right-angle, we can find angle y by
; subtracting angle x from pi/2.
; However it's just as easy to reduce the argument first and subtract the
; reduced argument from the value 1 (a reduced right-angle).
; It's even easier to subtract 1 from the angle and rectify the sign.
; In fact, after reducing the argument, the absolute value of the argument
; is used and rectified using the test result stored in mem-0 by 'get-argt'
; for that purpose.
;
;; cos
L37AA: RST 28H ;; FP-CALC angle in radians.
DB $39 ;;get-argt X reduce -1 to +1
DB $2A ;;abs ABS X. 0 to 1
DB $A1 ;;stk-one ABS X, 1.
DB $03 ;;subtract now opposite angle
;; although sign is -ve.
DB $E0 ;;get-mem-0 fetch the sign indicator
DB $00 ;;jump-true
DB $06 ;;fwd to L37B7, C-ENT
;;forward to common code if in QII or QIII.
DB $1B ;;negate else make sign +ve.
DB $33 ;;jump
DB $03 ;;fwd to L37B7, C-ENT
;; with quadrants I and IV.
;--------------------
; THE 'SINE' FUNCTION
;--------------------
; (offset $1F: 'sin')
; This is a fundamental transcendental function from which others such as cos
; and tan are directly, or indirectly, derived.
; It uses the series generator to produce Chebyshev polynomials.
;
;
; /|
; 1 / |
; / |x
; /a |
; /----|
; y
;
; The 'get-argt' function is designed to modify the angle and its sign
; in line with the desired sine value and afterwards it can launch straight
; into common code.
;; sin
L37B5: RST 28H ;; FP-CALC angle in radians
DB $39 ;;get-argt reduce - sign now correct.
;; C-ENT
L37B7: DB $31 ;;duplicate
DB $31 ;;duplicate
DB $04 ;;multiply
DB $31 ;;duplicate
DB $0F ;;addition
DB $A1 ;;stk-one
DB $03 ;;subtract
DB $86 ;;series-06
DB $14 ;;Exponent: $64, Bytes: 1
DB $E6 ;;(+00,+00,+00)
DB $5C ;;Exponent: $6C, Bytes: 2
DB $1F,$0B ;;(+00,+00)
DB $A3 ;;Exponent: $73, Bytes: 3
DB $8F,$38,$EE ;;(+00)
DB $E9 ;;Exponent: $79, Bytes: 4
DB $15,$63,$BB,$23 ;;
DB $EE ;;Exponent: $7E, Bytes: 4
DB $92,$0D,$CD,$ED ;;
DB $F1 ;;Exponent: $81, Bytes: 4
DB $23,$5D,$1B,$EA ;;
DB $04 ;;multiply
DB $38 ;;end-calc
RET ; return.
;-----------------------
; THE 'TANGENT' FUNCTION
;-----------------------
; (offset $21: 'tan')
;
; Evaluates tangent x as sin(x) / cos(x).
;
;
; /|
; h / |
; / |o
; /x |
; /----|
; a
;
; the tangent of angle x is the ratio of the length of the opposite side
; divided by the length of the adjacent side. As the opposite length can
; be calculates using sin(x) and the adjacent length using cos(x) then
; the tangent can be defined in terms of the previous two functions.
; Error 6 if the argument, in radians, is too close to one like pi/2
; which has an infinite tangent. e.g. PRINT TAN (PI/2) evaluates as 1/0.
; Similarly PRINT TAN (3*PI/2), TAN (5*PI/2) etc.
;; tan
L37DA: RST 28H ;; FP-CALC x.
DB $31 ;;duplicate x, x.
DB $1F ;;sin x, sin x.
DB $01 ;;exchange sin x, x.
DB $20 ;;cos sin x, cos x.
DB $05 ;;division sin x/cos x (= tan x).
DB $38 ;;end-calc tan x.
RET ; return.
;----------------------
; THE 'ARCTAN' FUNCTION
;----------------------
; (Offset $24: 'atn')
; the inverse tangent function with the result in radians.
; This is a fundamental transcendental function from which others such as asn
; and acs are directly, or indirectly, derived.
; It uses the series generator to produce Chebyshev polynomials.
;; atn
L37E2: CALL L3297 ; routine re-stack
LD A,(HL) ; fetch exponent byte.
CP $81 ; compare to that for 'one'
JR C,L37F8 ; forward, if less, to SMALL
RST 28H ;; FP-CALC
DB $A1 ;;stk-one
DB $1B ;;negate
DB $01 ;;exchange
DB $05 ;;division
DB $31 ;;duplicate
DB $36 ;;less-0
DB $A3 ;;stk-pi/2
DB $01 ;;exchange
DB $00 ;;jump-true
DB $06 ;;to L37FA, CASES
DB $1B ;;negate
DB $33 ;;jump
DB $03 ;;to L37FA, CASES
;; SMALL
L37F8: RST 28H ;; FP-CALC
DB $A0 ;;stk-zero
;; CASES
L37FA: DB $01 ;;exchange
DB $31 ;;duplicate
DB $31 ;;duplicate
DB $04 ;;multiply
DB $31 ;;duplicate
DB $0F ;;addition
DB $A1 ;;stk-one
DB $03 ;;subtract
DB $8C ;;series-0C
DB $10 ;;Exponent: $60, Bytes: 1
DB $B2 ;;(+00,+00,+00)
DB $13 ;;Exponent: $63, Bytes: 1
DB $0E ;;(+00,+00,+00)
DB $55 ;;Exponent: $65, Bytes: 2
DB $E4,$8D ;;(+00,+00)
DB $58 ;;Exponent: $68, Bytes: 2
DB $39,$BC ;;(+00,+00)
DB $5B ;;Exponent: $6B, Bytes: 2
DB $98,$FD ;;(+00,+00)
DB $9E ;;Exponent: $6E, Bytes: 3
DB $00,$36,$75 ;;(+00)
DB $A0 ;;Exponent: $70, Bytes: 3
DB $DB,$E8,$B4 ;;(+00)
DB $63 ;;Exponent: $73, Bytes: 2
DB $42,$C4 ;;(+00,+00)
DB $E6 ;;Exponent: $76, Bytes: 4
DB $B5,$09,$36,$BE ;;
DB $E9 ;;Exponent: $79, Bytes: 4
DB $36,$73,$1B,$5D ;;
DB $EC ;;Exponent: $7C, Bytes: 4
DB $D8,$DE,$63,$BE ;;
DB $F0 ;;Exponent: $80, Bytes: 4
DB $61,$A1,$B3,$0C ;;
DB $04 ;;multiply
DB $0F ;;addition
DB $38 ;;end-calc
RET ; return.
;----------------------
; THE 'ARCSIN' FUNCTION
;----------------------
; (Offset $22: 'asn')
; the inverse sine function with result in radians.
; derived from arctan function above.
; Error A unless the argument is between -1 and +1 inclusive.
; uses an adaptation of the formula asn(x) = atn(x/sqr(1-x*x))
;
;
; /|
; 1 / |
; / |x
; /a |
; /----|
; y
;
; e.g. we know the opposite side (x) and hypotenuse (1)
; and we wish to find angle a in radians.
; we can derive length y by Pythagorus and then use ATN instead.
; since y*y + x*x = 1*1 (Pythagorus Theorem) then
; y=sqr(1-x*x) - no need to multiply 1 by itself.
; so, asn(a) = atn(x/y)
; or more fully,
; asn(a) = atn(x/sqr(1-x*x))
; Close but no cigar.
; While PRINT ATN (x/SQR (1-x*x)) gives the same results as PRINT ASN x,
; it leads to division by zero when x is 1 or -1.
; To overcome this, 1 is added to y giving half the required angle and the
; result is then doubled.
; That is PRINT ATN (x/(SQR (1-x*x) +1)) *2
; A value higher than 1 gives the required error as attempting to find the
; square root of a negative number generates an error in Sinclair BASIC.
;; asn
L3833: RST 28H ;; FP-CALC x.
DB $31 ;;duplicate x, x.
DB $31 ;;duplicate x, x, x.
DB $04 ;;multiply x, x*x.
DB $A1 ;;stk-one x, x*x, 1.
DB $03 ;;subtract x, x*x-1.
DB $1B ;;negate x, 1-x*x.
DB $28 ;;sqr x, sqr(1-x*x) = y
DB $A1 ;;stk-one x, y, 1.
DB $0F ;;addition x, y+1.
DB $05 ;;division x/y+1.
DB $24 ;;atn a/2 (half the angle)
DB $31 ;;duplicate a/2, a/2.
DB $0F ;;addition a.
DB $38 ;;end-calc a.
RET ; return.
;-------------------------
; THE 'ARCCOS' FUNCTION
;-------------------------
; (Offset $23: 'acs')
; the inverse cosine function with the result in radians.
; Error A unless the argument is between -1 and +1.
; Result in range 0 to pi.
; Derived from asn above which is in turn derived from the preceding atn.
; It could have been derived directly from atn using acs(x) = atn(sqr(1-x*x)/x).
; However, as sine and cosine are horizontal translations of each other,
; uses acs(x) = pi/2 - asn(x)
; e.g. the arccosine of a known x value will give the required angle b in
; radians.
; We know, from above, how to calculate the angle a using asn(x).
; Since the three angles of any triangle add up to 180 degrees, or pi radians,
; and the largest angle in this case is a right-angle (pi/2 radians), then
; we can calculate angle b as pi/2 (both angles) minus asn(x) (angle a).
;
;
; /|
; 1 /b|
; / |x
; /a |
; /----|
; y
;
;; acs
L3843: RST 28H ;; FP-CALC x.
DB $22 ;;asn asn(x).
DB $A3 ;;stk-pi/2 asn(x), pi/2.
DB $03 ;;subtract asn(x) - pi/2.
DB $1B ;;negate pi/2 -asn(x) = acs(x).
DB $38 ;;end-calc acs(x).
RET ; return.
; --------------------------
; THE 'SQUARE ROOT' FUNCTION
; --------------------------
; (Offset $28: 'sqr')
; This routine is remarkable only in its brevity - 7 bytes.
; It wasn't written here but in the ZX81 where the programmers had to squeeze
; a bulky operating sytem into an 8K ROM. It simply calculates
; the square root by stacking the value .5 and continuing into the 'to-power'
; routine. With more space available the much faster Newton-Raphson method
; should have been used as on the Jupiter Ace.
;; sqr
L384A: RST 28H ;; FP-CALC
DB $31 ;;duplicate
DB $30 ;;not
DB $00 ;;jump-true
DB $1E ;;to L386C, LAST
DB $A2 ;;stk-half
DB $38 ;;end-calc
; ------------------------------
; THE 'EXPONENTIATION' OPERATION
; ------------------------------
; (Offset $06: 'to-power')
; This raises the first number X to the power of the second number Y.
; As with the ZX80,
; 0 ^ 0 = 1.
; 0 ^ +n = 0.
; 0 ^ -n = arithmetic overflow.
;
;; to-power
L3851: RST 28H ;; FP-CALC X, Y.
DB $01 ;;exchange Y, X.
DB $31 ;;duplicate Y, X, X.
DB $30 ;;not Y, X, (1/0).
DB $00 ;;jump-true
DB $07 ;;to L385D, XISO if X is zero.
; else X is non-zero. Function 'ln' will catch a negative value of X.
DB $25 ;;ln Y, LN X.
DB $04 ;;multiply Y * LN X.
DB $38 ;;end-calc
JP L36C4 ; jump back to EXP routine ->
; ---
; these routines form the three simple results when the number is zero.
; begin by deleting the known zero to leave Y the power factor.
;; XISO
L385D: DB $02 ;;delete Y.
DB $31 ;;duplicate Y, Y.
DB $30 ;;not Y, (1/0).
DB $00 ;;jump-true
DB $09 ;;to L386A, ONE if Y is zero.
DB $A0 ;;stk-zero Y, 0.
DB $01 ;;exchange 0, Y.
DB $37 ;;greater-0 0, (1/0).
DB $00 ;;jump-true 0.
DB $06 ;;to L386C, LAST if Y was any positive
;; number.
; else force division by zero thereby raising an Arithmetic overflow error.
; There are some one and two-byte alternatives but perhaps the most formal
; might have been to use end-calc; rst 08; DB 05.
DB $A1 ;;stk-one 0, 1.
DB $01 ;;exchange 1, 0.
DB $05 ;;division 1/0 ouch!
; ---
;; ONE
L386A: DB $02 ;;delete .
DB $A1 ;;stk-one 1.
;; LAST
L386C: DB $38 ;;end-calc last value is 1 or 0.
RET ; return. Whew!
;*********************************
;** Spectrum 128 Patch Routines **
;*********************************
; The new code added to the standard 48K Spectrum ROM is mainly devoted to the scanning and decoding of the keypad.
; These routines occupy addresses 386E through to 3B3A. Addresses 3B3B through to 3C96 contain a variety of routines for the following purposes: displaying the new tokens 'PLAY' and 'SPECTRUM',
; dealing with the keypad when using INKEY$, handling new 128 BASIC error messages, and producing the TV tuner display. Addresses 3BE1 to 3BFE and addresses 3C97 to 3CFF are unused and all contain 00.
; Documented by Paul Farrow.
; --------------------------------
; SCAN THE KEYPAD AND THE KEYBOARD
; --------------------------------
; This patch will attempt to scan the keypad if in 128K mode and will then scan the keyboard.
;; KEYS
L386E: PUSH IX
BIT 4,(IY+$01) ; [FLAGS] Test if in 128K mode
JR Z,L3879 ; Z=in 48K mode
CALL L3A42 ; Attempt to scan the keypad
;; KEYS_CONT
L3879: CALL L02BF ; Scan the keyboard
POP IX
RET
; ----------------------------------
; READ THE STATE OF THE OUTPUT LINES
; ----------------------------------
; This routine returns the state of the four output lines (bits 0-3) in the lower four bits of L. The LSB of L corresponds to the output communication line to the keypad.
; In this way the state of the other three outputs are maintained when the state of the LSB of L is changed and sent out to register 14 of the AY-3-8912.
;; READ_OUTPUTS
L387F: LD C,$FD ; FFFD = Address of the
LD D,$FF ; command register (register 7)
LD E,$BF ; BFFD = Address of the
LD B,D ; data register (register 14)
LD A,$07
OUT (C),A ; Select command register
IN H,(C) ; Read its status
LD A,$0E
OUT (C),A ; Select data register
IN A,(C) ; Read its status
OR $F0 ; Mask off the input lines
LD L,A ; L=state of output lines at the
RET ; keypad socket
; --------------------------
; SET THE OUTPUT LINE, BIT 0
; --------------------------
; The output line to the keypad is set via the LSB of L.
;; SET_REG14
L3896: LD B,D
LD A,$0E
OUT (C),A ; Select the data register
LD B,E
OUT (C),L ; Send L out to the data register
RET ; Set the output line
; ----------------------------------------
; FETCH THE STATE OF THE INPUT LINE, BIT 5
; ----------------------------------------
; Return the state of the input line from the keypad in bit 5 of A.
;; GET_REG14
L389F: LD B,D
LD A,$0E
OUT (C),A ; Select the data register
IN A,(C) ; Read the input line
RET
; ------------------------------
; SET THE OUTPUT LINE LOW, BIT 0
; ------------------------------
;; RESET_LINE
L38A7: LD A,L
AND $FE ; Reset bit 0 of L
LD L,A
JR L3896 ; Send out L to the data register
; -------------------------------
; SET THE OUTPUT LINE HIGH, BIT 0
; -------------------------------
;; SET_LINE
L38AD: LD A,L
OR $01 ; Set bit 0 of L
LD L,A
JR L3896 ; Send out L to the data register
; -------------------
; MINOR DELAY ROUTINE
; -------------------
; Delay for (B*13)+5 T-States.
;; DELAY
L38B3: DJNZ L38B3
RET
; -------------------
; MAJOR DELAY ROUTINE
; -------------------
; Delay for (B*271)+5 T-states.
;; DELAY2
L38B6: PUSH BC
LD B,$10
CALL L38B3 ; Inner delay of 135 T-States
POP BC
DJNZ L38B6
RET
; ------------------------------------
; MONITOR FOR THE INPUT LINE TO GO LOW
; ------------------------------------
; Monitor the input line, bit 5, for up to (B*108)+5 T-states.
;; MON_B5_LO
L38C0: PUSH BC
CALL L389F ; Read the state of the input line
POP BC
AND $20 ; Test bit 5, the input line
JR Z,L38CB ; Exit if input line found low
DJNZ L38C0 ; Repeat until timeout expires
;; EXT_MON_LO
L38CB: RET
; -------------------------------------
; MONITOR FOR THE INPUT LINE TO GO HIGH
; -------------------------------------
; Monitor the input line, bit 5, for up to (B*108)+5 T-states.
;; MON_B5_HI
L38CC: PUSH BC
CALL L389F ; Read the state of the input line
POP BC
AND $20 ; Test bit 5, the input line
JR NZ,L38D7 ; Exit if input line found low
DJNZ L38CC ; Repeat until timeout expires
;; EXT_MON_HI
L38D7: RET
; -------------------------
; READ KEY PRESS STATUS BIT
; -------------------------
; This entry point is used to read in the status bit for a keypad row. If a key is being pressed in the current row then the bit read in will be a 1.
;; READ_STATUS
L38D8: CALL L387F ; Read the output lines
LD B,$01 ; Read in one bit
JR L38E4
; ----------------
; READ IN A NIBBLE
; ----------------
; This entry point is used to read in a nibble of data from the keypad. It is used for two functions. The first is to read in the poll nibble and the second is to read in a row of key press data.
; For a nibble of key press data, a bit read in as 1 indicates that the corresponding key was pressed.
;; READ_NIBBLE
L38DF: CALL L387F ; Read the state of the output lines
LD B,$04 ; Read in four bits
;; READ_BIT
L38E4: PUSH BC
CALL L389F ; Read the input line from the keypad
POP BC
AND $20 ; This line should initially be high
JR Z,L392D ; Z=read in a 0, there must be an error
XOR A ; The bits read in will be stored in register A
;; BIT_LOOP
L38EE: PUSH BC ; Preserve the loop count and any bits
PUSH AF ; read in so far
CALL L38AD ; Set the output line high
LD B,$A3 ; Monitor for 17609 T-states for the
CALL L38C0 ; input line to go low
JR NZ,L392B ; NZ=the line did not go low
CALL L38A7 ; Set the output line low
JR L3901 ; Insert a delay of 12 T-states
L38FF: DB $FF, $FF
;; BL_CONTINUE
L3901: LD B,$2B ; Delay for 564 T-states
CALL L38B3
CALL L389F ; Read in the bit value
BIT 5,A
JR Z,L3911 ; Z=read in a 0
POP AF ; Retrieve read in bits
SCF ; Set carry bit
JR L3914
;; BL_READ_0
L3911: POP AF ; Retrieve read in bits
SCF
CCF ; Clear carry bit
;; BL_STORE
L3914: RRA ; Shift the carry bit into bit 0 of A
PUSH AF ; Save bits read in
CALL L38AD ; Set the output line high
LD B,$26 ; Delay for 499 T-states
CALL L38B3
CALL L38A7 ; Set the output line low
LD B,$23 ; Delay for 460 T-states
CALL L38B3
POP AF ; Retrieve read in bits
POP BC ; Retrieve loop counter and repeat
DJNZ L38EE ; for all bits to read in
RET
; ----------
; LINE ERROR
; ----------
; The input line was found at the wrong level. The output line is now set high which will eventually cause the keypad to abandon its transmissions.
; The upper nibble of system variable FLAGS/ROW3 will be cleared to indicate that communications to the keypad is no longer in progress.
;; LINE_ERROR
L392B: POP AF
POP BC ; Clear the stack
;; LINE_ERROR2
L392D: CALL L38AD ; Set the output line high
XOR A ; Clear FLAGS nibble
LD ($5B88),A ; [FLAGS/ROW3]
INC A ; Return zero flag reset
SCF
CCF ; Return carry flag reset
RET
; ---------------
; POLL THE KEYPAD
; ---------------
; The Spectrum 128 polls the keypad by changing the state of the output line and monitoring for responses from the keypad on the input line.
; Before a poll occurs, the poll counter must be decremented until it reaches zero. This counter causes a delay of three seconds before a communications attempt to the keypad is made.
; The routine can exit at five different places and it is the state of the A register, the zero flag and the carry flag which indicates the cause of the exit. This is summarised below:
;
; A Register Zero Flag Carry Flag Cause
; 0 set set Communications already established
; 0 set reset Nibble read in OK
; 1 reset reset Nibble read in with an error or i/p line initially low
; 1 reset set Poll counter has not yet reached zero
;
; The third bit of the nibble read in must be set for the poll to be subsequently accepted.
;; ATTEMPT_POLL
L3938: CALL L387F ; Read the output line states
LD A,($5B88) ; [FLAGS/ROW3] Has communications already been
AND $80 ; established with the keypad?
JR NZ,L3999 ; NZ=yes, so skip the poll
CALL L389F ; Read the input line
AND $20 ; It should be high initially
JR Z,L392D ; Z=error, input line found low
LD A,($5B88) ; [FLAGS/ROW3] Test if poll counter already zero thus
AND A ; indicating a previous comms error
JR NZ,L395A ; NZ=ready to poll the keypad
INC A ; Indicate comms not established
LD ($5B88),A ; [FLAGS/ROW3]
LD A,$4C ; Reset the poll counter
LD ($5B89),A ; [ROW2/ROW1]
JR L399C ; Exit the routine
;;POLL_KEYPAD
L395A: LD A,($5B89) ; [ROW2/ROW1] Decrement the poll counter
DEC A
LD ($5B89),A ; [ROW2/ROW1]
JR NZ,L399C ; Exit the routine if it is not yet zero
; The poll counter has reached zero so a poll of the keypad can now occur.
XOR A
LD ($5B88),A ; [FLAGS/ROW3] Indicate that a poll can occur
LD ($5B89),A ; [ROW2/ROW1]
LD ($5B8A),A ; [ROW4/ROW5] Clear all the row nibble stores
CALL L38A7 ; Set the output line low
LD B,$21 ; Wait up to 3569 T-States for the
CALL L38C0 ; input line to go low
JR NZ,L392D ; NZ=line did not go low
CALL L38AD ; Set the output line high
LD B,$24 ; Wait up to 3893 T-States for the
CALL L38CC ; input line to go high
JR Z,L392D ; NZ=line did not go high
CALL L38A7 ; Set the output line low
LD B,$0F
CALL L38B6 ; Delay for 4070 T-States
CALL L38DF ; Read in a nibble of data
JR NZ,L392D ; NZ=error occurred when reading in nibble
SET 7,A ; Set bit 7
AND $F0 ; Keep only the upper four bits
; (Bit 6 will be set if poll successful)
LD ($5B88),A ; [FLAGS/ROW3] Store the flags nibble
XOR A
SRL A ; Exit: Zero flag set, Carry flag reset
RET
;; AP_SKIP_POLL
L3999: XOR A ; Communications already established
SCF ; Exit: Zero flag set, Carry flag set
RET
;; PK_EXIT
L399C: XOR A ; Poll counter not zero
INC A
SCF ; Exit: Zero flag reset, Carry flag set
RET
; -----------------------
; SCAN THE KEYPAD ROUTINE
; -----------------------
; If a successful poll of the keypad occurs then the five rows of keys are read in and a unique key code generated.
;; KEYPAD_SCAN
L39A0: CALL L3938 ; Try to poll the keypad
LD A,($5B88) ; [FLAGS/ROW3] Test the flags nibble
CPL
AND $C0 ; Bits 6 and 7 must be set in FLAGS
RET NZ ; NZ=poll was not successful
; The poll was successful so now read in data for the five keypad rows.
LD IX,$5B8A ; [ROW4/ROW5]
LD B,$05 ; The five rows
;; KS_LOOP
L39B0: PUSH BC ; Save counter
CALL L38D8 ; Read the key press status bit
JP NZ,L3A3A ; NZ=error occurred
BIT 7,A ; Test the bit read in
JR Z,L39DC ; Z=no key pressed in this row
CALL L38DF ; Read in the row's nibble of data
JR NZ,L3A3A ; NZ=error occurred
POP BC ; Fetch the nibble loop counter
PUSH BC
LD C,A ; Move the nibble read in to C
LD A,(IX+$00) ; Fetch the nibble store
BIT 0,B ; Test if an upper or lower nibble
JR Z,L39D6 ; Z=upper nibble
SRL C ; Shift the nibble to the lower position
SRL C
SRL C
SRL C
AND $F0 ; Mask off the lower nibble of the
JR L39D8 ; nibble store
;; KS_UPPER
L39D6: AND $0F ; Mask off the upper nibble of the nibble store
;; KS_STORE
L39D8: OR C ; Combine the existing and new
LD (IX+$00),A ; nibbles and store them
;; KS_NEXT
L39DC: POP BC ; Retrieve the row counter
BIT 0,B ; Test if next nibble store is required
JR NZ,L39E3 ; NZ=use same nibble store
DEC IX ; Point to the next nibble store
;; KS_NEW
L39E3: DJNZ L39B0 ; Repeat for the next keypad row
; All five rows have now been read so compose a unique code for the key pressed.
LD E,$80 ; Signal no key press found yet
LD IX,$5B88 ; [FLAGS/ROW3]
LD HL,$3A3F ; Point to the key mask data
LD B,$03 ; Scan three nibbles
;; GEN_LOOP
L39F0: LD A,(IX+$00) ; Fetch a pair of nibbles
AND (HL) ; This will mask off the FLAGS nibble and the SHIFT/0 key
JR Z,L3A17 ; Z=no key pressed in these nibbles
BIT 7,E ; Test if a key has already been found
JR Z,L3A3C ; Z=multiple keys pressed
PUSH BC ; Save the loop counter
PUSH AF ; Save the byte of key bit data
LD A,B ; Move loop counter to A
JR L3A01 ; A delay of 12 T-States
L39FF: DB $FF, $FF ; Unused locations
;; GEN_CONT
L3A01: DEC A ; These lines of code generate base
SLA A ; values of 7, 15 and 23 for the three
SLA A ; nibble stores 5B88, 5B89 & 5B8A.
SLA A
OR $07
LD B,A ; B=(loop counter-1)*8+7
POP AF ; Fetch the byte of key press data
;; GEN_BIT
L3A0C: SLA A ; Shift until a set key bit drops into the
JP C,L3A13 ; carry flag
DJNZ L3A0C ; Decrement B for each 'unsuccessful' shift of the A register
;; GEN_FOUND
L3A13: LD E,B ; E=a unique number for the key pressed, between 1 - 19 except 2 & 3
POP BC ; As a result shifting the set key bit
; into the carry flag, the A register will
; hold 00 if only one key was pressed
JR NZ,L3A3C ; NZ=multiple keys pressed
;; GEN_NEXT
L3A17: INC IX ; Point to the next nibble store
INC HL ; Point to the corresponding mask data
DJNZ L39F0 ; Repeat for all three 'nibble' bytes
BIT 7,E ; Test if any keys were pressed
JR NZ,L3A27 ; NZ=no keys were pressed
LD A,E ; Copy the key code
AND $FC ; Test for the '.' key (E=1)
JR Z,L3A27 ; Z='.' key pressed
DEC E
DEC E ; Key code in range 2 - 17
; The E register now holds a unique key code value between 1 and 17.
;; GEN_POINT
L3A27: LD A,($5B8A) ; [ROW4/ROW5] Test if the SHIFT key was pressed
AND $08
JR Z,L3A34 ; Z=the SHIFT key was not pressed
; The SHIFT key was pressed or no key was pressed.
LD A,E ; Fetch the key code
AND $7F ; Mask off 'no key pressed' bit
ADD A,$12 ; Add on a shift offset of 12
LD E,A
; Add a base offset of 5A to all key codes. Note that no key press will result in a key code of DA. This is the only code with bit 7 set and so will be detected later.
;; GEN_NOSHIFT
L3A34: LD A,E
ADD A,$5A ; Add a base offset of 5A
LD E,A ; Return key codes in range 5B - 7D
XOR A
RET ; Exit: Zero flag set, key found OK
; These two lines belong with the loop above to read in the five keypad rows and are jumped to when an error occurs during reading in a nibble of data.
;; KS_ERROR
L3A3A: POP BC ; Clear the stack and exit
RET ; Exit: Zero flag reset
;; GEN_INVALID
L3A3C: XOR A ; Exit: Zero flag reset indicating an
INC A ; invalid key press
RET
; ----------------
; KEYPAD MASK DATA
; ----------------
;; KEY_MASKS
L3A3F: DB $0F, $FF, $F2 ; Key mask data
; ---------------
; READ THE KEYPAD
; ---------------
; This routine reads the keypad and handles key repeat and decoding. The bulk of the key repeat code is very similar to that used in the equivalent keyboard routine and works are follows.
; A double system of KSTATE system variables (KSTATE0 - KSTATE3 and KSTATE4 - KSTATE7) is used to allow the detection of one key while in the repeat period of the previous key.
; In this way, a 'spike' from another key will not stop the previous key from repeating. For a new key to be acknowledged, it must be held down for at least 1/5th of a second, i.e. ten calls to KEYPAD.
; The KSTATE system variables store the following data:
;
; KSTATE0/4 Un-decoded Key Value (00-27 for keyboard, 5B-7D for keypad, FF for no key)
; KSTATE1/5 10 Call Counter
; KSTATE2/6 Repeat Delay
; KSTATE3/7 Decoded Key Value
;
; The code returned is then stored in system variable LAST_K (5C08) and a new key signalled by setting bit 5 of FLAGS (5C3B).
;
; If the Spectrum 128 were to operate identically to the standard 48K Spectrum when in 48K mode, it would have to spend zero time in reading the keypad.
; As this is not possible, the loading on the CPU is reduced by scanning the keypad upon every other interrupt. A '10 Call Counter' is then used to ensure that a key is held down for at least 1/5th of a second
; before it is registered. Note that this is twice as long as for keyboard key presses and so the keypad key repeat delay is halved.
;
; At every other interrupt the keypad scanning routine is skipped. The net result of the routine is simply to decrement both '10 Call Counters', if appropriate. By loading the E register with 80 ensures that
; the call to KP_TEST will reject the key code and cause a return. A test for keyboard key codes prevents the Call Counter decrements affecting a keyboard key press. It would have been more efficient to execute
; a return upon every other call to KEYPAD and then to have used a '5 Call Counter' just as the keyboard routine does.
;
; A side effect of both the keyboard and keypad using the same KSTATE system variables is that if a key is held down on the keypad and then a key is held down on the keyboard, both keys will be monitored and
; repeated alternatively, but with a reduced repeat delay. This delay is between the keypad key repeat delay and the keyboard key repeat delay. This occurs because both the keypad and keyboard routines will
; decrement the KSTATE system variable Call Counters. The keypad routine 'knows' of the existence of keyboard key codes but the reverse is not true.
;; KEYPAD
L3A42: LD E,$80 ; Signal no key pressed
LD A,($5C78) ; [FRAMES]
AND $01 ; Scan the keypad every other
JR NZ,L3A4F ; interrupt
CALL L39A0
RET NZ ; NZ=no valid key pressed
;; KP_CHECK
L3A4F: LD HL,$5C00 ; [KSTATE0] Test the first KSTATE variable
;; KP_LOOP
L3A52: BIT 7,(HL) ; Is the set free?
JR NZ,L3A62 ; NZ=yes
LD A,(HL) ; Fetch the un-decoded key value
CP $5B ; Is it a keyboard code?
JR C,L3A62 ; C=yes, so do not decrement counter
INC HL
DEC (HL) ; Decrement the 10 Call Counter
DEC HL
JR NZ,L3A62 ; If the counter reaches zero, then
; signal the set is free
LD (HL),$FF
;; KP_CH_SET
L3A62: LD A,L ; Jump back and test the second set if
LD HL,$5C04 ; [KSTATE4] not yet considered
CP L
JR NZ,L3A52
CALL L3AAE ; Test for valid key combinations and
RET NZ ; return if invalid
LD A,E ; Test if the key in the first set is being
LD HL,$5C00 ; [KSTATE0] repeated
CP (HL)
JR Z,L3A9E ; Jump if being repeated
EX DE,HL ; Save the address of KSTATE0
LD HL,$5C04 ; [KSTATE4] Test if the key in the second set is
CP (HL) ; being repeated
JR Z,L3A9E ; Jump if being repeated
; A new key will not be accepted unless one of the KSTATE sets is free.
BIT 7,(HL) ; Test if the second set is free
JR NZ,L3A83 ; Jump if set is free
EX DE,HL
BIT 7,(HL) ; Test if the first set is free
RET Z ; Return if no set is free
;; KP_NEW
L3A83: LD E,A ; Pass the key code to the E register
LD (HL),A ; and to KSTATE0/4
INC HL
LD (HL),$0A ; Set the '10 Call Counter' to 10
INC HL
LD A,($5C09) ; [REPDEL] Fetch the initial repeat delay
SRL A ; Divide delay by two
LD (HL),A ; Store the repeat delay
INC HL
CALL L3AD7 ; Decode the keypad key code
LD (HL),E ; and store it in KSTATE3/7
; This section is common for both new keys and repeated keys.
;; KP_END
L3A94: LD A,E
LD ($5C08),A ; [LAST_K] Store the key value in LAST_K
LD HL,$5C3B ; FLAGS
SET 5,(HL) ; Signal a new key pressed
RET
; -------------------------
; THE KEY REPEAT SUBROUTINE
; -------------------------
;; KP_REPEAT
L3A9E: INC HL
LD (HL),$0A ; Reset the '10 Call Counter' to 10
INC HL
DEC (HL) ; Decrement the repeat delay
RET NZ ; Return if not zero
LD A,($5C0A) ; [REPPER] The subsequent repeat delay is
SRL A ; divided by two and stored
LD (HL),A
INC HL
LD E,(HL) ; The key repeating is fetched
JR L3A94 ; and then returned in LAST_K
; ----------------------------------------
; THE TEST FOR A VALID KEY CODE SUBROUTINE
; ----------------------------------------
; The zero flag is returned set if the key code is valid. No key press, SHIFT only or invalid shifted key presses return the zero flag reset.
;; KP_TEST
L3AAE: LD A,E
LD HL,$5B66 ; FLAGS3 Test if in BASIC or EDIT mode
BIT 0,(HL)
JR Z,L3ABC ; Z=EDIT mode
; Test key codes when in BASIC/CALCULATOR mode
CP $6D ; Test for shifted keys
JR NC,L3AD4 ; and signal an error if found
;; KPT_OK
L3ABA: XOR A ; Signal valid key code
RET ; Exit: Zero flag set
; Test key codes when in EDIT/MENU mode.
;; KPT_EDIT
L3ABC: CP $80 ; Test for no key press
JR NC,L3AD4 ; NC=no key press
CP $6C ; Test for SHIFT on its own
JR NZ,L3ABA ; NZ=valid key code
L3AC4: DB $00, $00, $00 ; Delay for 64 T-States
DB $00, $00, $00
DB $00, $00, $00
DB $00, $00, $00
DB $00, $00, $00
DB $00
;; KPT_INVALID
L3AD4: XOR A ; Signal invalid key code
INC A
RET ; Exit: Zero flag reset
; ---------------------------
; THE KEY DECODING SUBROUTINE
; ---------------------------
;; KP_DECODE
L3AD7: PUSH HL ; Save the KSTATE pointer
LD A,E
SUB $5B ; Reduce the key code range to
LD D,$00 ; 00 - 22 and transfer to DE
LD E,A
LD HL,$5B66 ; FLAGS3 Test if in EDIT or BASIC mode
BIT 0,(HL)
JR Z,L3AEA ; Z=EDIT/MENU mode
; Use Table 1 when in CALCULATOR/BASIC mode.
LD HL,L3B13
JR L3B0F ; Look up the key value
; Deal with EDIT/MENU mode.
;; KPD_EDIT
L3AEA: LD HL,L3B25 ; Use Table 4 for unshifted key
CP $11 ; presses
JR C,L3B0F
; Deal with shifted keys in EDIT/MENU mode.
; Use Table 3 with SHIFT 1 (delete to beginning of line), SHIFT 2 (delete to end of line), SHIFT 3 (SHIFT TOGGLE). Note that although SHIFT TOGGLE produces a unique valid code,
; it actually performs no function when editing a BASIC program.
LD HL,L3B21
CP $15 ; Test for SHIFT 1
JR Z,L3B0F
CP $16 ; Test for SHIFT 2
JR Z,L3B0F
JR L3B01 ; Delay for 12 T-States
L3AFE: DB $00, $FF, $FF ; Unused locations
;; KPD_CONT
L3B01: CP $17 ; Test for SHIFT 3
JR Z,L3B0F
; Use Table 2 with SHIFT 4 (delete to beginning of word) and SHIFT 5 (delete to end of word).
LD HL,L3B18
CP $21 ; Test for SHIFT 4 and above
JR NC,L3B0F
;Use Table 1 for all other shifted key presses.
LD HL,L3B13
;; KPD_EXIT
L3B0F: ADD HL,DE ; Look up the key value
LD E,(HL)
POP HL ; Retrieve the KSTATE address
RET
; --------------------------------
; THE KEYPAD DECODE LOOK-UP TABLES
; --------------------------------
;; KPD_TABLE1
L3B13: DB $2E, $0D, $33 ; '.', ENTER, 3
DB $32, $31 ; 2, 1
;; KPD_TABLE2
L3B18: DB $29, $28, $2A ; ), (, *
DB $2F, $2D, $39 ; /, - , 9
DB $38, $37, $2B ; 8, 7, +
;; KPD_TABLE3
L3B21: DB $36, $35, $34 ; 6, 5, 4
DB $30 ; 0
;; KPD_TABLE4
L3B25: DB $A5, $0D, $A6 ; Bottom, ENTER, Top
DB $A7, $A8, $A9 ; End of line, Start of line, TOGGLE
DB $AA, $0B, $0C ; DEL right, Up, DEL
DB $07, $09, $0A ; CMND, Right, Down
DB $08, $AC, $AD ; Left, Down ten, Up ten
DB $AE, $AF ; End word, Beginning of word
DB $B0, $B1, $B2 ; DEL to end of line, DEL to start of line, SHIFT TOGGLE
DB $B3, $B4 ; DEL to end of word, DEL to beginning of word
; -----------------------------
; PRINT NEW ERROR MESSAGE PATCH
; -----------------------------
L3B3B: BIT 4,(IY+$01) ; FLAGS 3 - In 128K mode?
JR NZ,L3B46 ; NZ=128K mode
; In 48K mode
XOR A ; Replicate code from standard ROM that the patch over-wrote
LD DE,$1536
RET
; In 128K mode
L3B46: LD HL,$010F ; Vector table entry in Editor ROM -> JP $03A2
; Return to Editor ROM at address in HL
L3B49: EX (SP),HL ; Change the return address
JP $5B00 ; Page Editor ROM and return to the address on the stack
; -------------------------------------
; STATEMENT INTERPRETATION RETURN PATCH
; -------------------------------------
L3B4D: BIT 4,(IY+$01) ; In 128K mode?
JR NZ,L3B58 ; NZ=128K mode
; In 48K mode
BIT 7,(IY+$0A) ; replicate code from standard ROM that the patch over-wrote
RET
; In 128K mode
L3B58: LD HL,$0112 ; Handle in Editor ROM by jumping to Vector table entry in Editor ROM -> JP #182A
JR L3B49
; --------------------------
; GO TO NEXT STATEMENT PATCH
; --------------------------
L3B5D: BIT 4,(IY+$01) ; In 128K mode?
JR NZ,L3B67 ; NZ=128K mode
; In 48K mode
RST 18H ; replicate code from standard ROM that the patch over-wrote
CP $0D
RET
; In 128K mode
L3B67: LD HL,$0115 ; Handle in Editor ROM by jumping to Vector table entry in Editor ROM -> JP #18A8
JR L3B49
; --------------------------------------
; INKEY$ ROUTINE TO DEAL WITH THE KEYPAD
; --------------------------------------
;; KEYSCAN2
L3B6C: CALL L028E ; KEYSCAN Scan the keyboard
LD C,$00
JR NZ,L3B80 ; NZ=multiple keys
CALL L031E ; K_TEST
JR NC,L3B80 ; NC=shift only or no key
DEC D
LD E,A
CALL L0333 ; K_DECODE
JP L2657 ; S_CONT Get string and continue scanning
;; KPI_SCAN
L3B80: BIT 4,(IY+$01) ; 128K mode?
JP Z,L2660 ; S_IK$_STK Z=no, stack keyboard code
DI ; Disable interrupts whilst scanning
CALL L39A0 ; the keypad
EI
JR NZ,L3B9A ; NZ=multiple keys
CALL L3AAE ; Test the keypad
JR NZ,L3B9A ; NZ=no key, shift only or invalid combination
CALL L3AD7 ; Form the key code
LD A,E
JP L2657 ; S_CONT Get string and continue scanning
;; KPI_INVALID
L3B9A: LD C,$00 ; Signal no key, i.e. length=0
JP L2660 ; S_IK$_STK
; ---------------------
; PRINT TOKEN/UDG PATCH
; ---------------------
L3B9F: CP $A3 ; SPECTRUM (T)
JR Z,L3BAF
CP $A4 ; PLAY (U)
JR Z,L3BAF
; In 48K mode here
L3BA7: SUB $A5 ; Check as per original ROM
JP NC,$0B5F
JP $0B56 ; Rejoin original ROM routine
L3BAF: BIT 4,(IY+$01) ; FLAGS3 - Bit 4=1 if in 128K mode
JR Z,L3BA7 ; Rejoin code for when in 48K mode
; In 128K mode here
LD DE,L3BC9
PUSH DE ; Stack return address
SUB $A3 ; Check whether the SPECTRUM token
LD DE,L3BD2 ; SPECTRUM token
JR Z,L3BC3
LD DE,L3BDA ; PLAY token
L3BC3: LD A,$04 ; Signal not RND, INKEY$ or PI so that a trailing space is printed
PUSH AF
JP L0C17 ; Rejoin printing routine PO-TABLE+3
; Return address from above
L3BC9: SCF ; Return as if no trailing space
BIT 1,(IY+$01) ; Test if printer is in use
RET NZ ; NZ=printer in use
JP $0B03 ; PO-FETCH - Return via Position Fetch routine
L3BD2 DC "SPECTRUM" ;DEFM "SPECTRU" ; SPECTRUM token
;DB 'M'+$80
L3BDA DC "PLAY" ;DEFM "PLA" ; PLAY token
;DB 'Y'+$80
;; KP_SCAN2
L3BDE: JP L3C01 ; This is not called from either ROM. It can be used to scan the keypad.
;===============================
PRINTER_INITER RST 8
DB _AY_PRN_INIT
RET
PRN_TOKEN RST 8
DB _AY_PRN_TOKEN
RET
DUPL 0X3BFF-$,0
DW 0XFFFF
;===============================
;; KP_SCAN
L3C01: JP L39A0 ; This was to be called via the vector table in the EDITOR ROM but due to a programming error it never gets called.
; -----------------------
; TV TUNER VECTOR ENTRIES
; -----------------------
L3C04: JP L3C10
L3C07: JP L3C10
L3C0A: JP L3C10
L3C0D: JP L3C10
; ----------------
; TV TUNER ROUTINE
; ----------------
; This routine generates a display showing all possible colours and emitting a continuous cycle of a 440Hz tone for 1 second followed by silence for 1 second.
; Its purpose is to ease the tuning in of TV sets to the Spectrum 128's RF signal. The display consists of vertical stripes of width four character squares showing each of the eight colours
; available at both their normal and bright intensities. The display begins with white on the left progressing up to black on the right. With in each colour stripe in the first eight rows is
; shown the year '1986' in varying ink colours. This leads to a display that shows all possible ink colours on all possible paper colours.
;; TV_TUNER
L3C10: LD A,$7F ; Test for the BREAK key
IN A,($FE)
RRA
RET C ; C=SPACE not pressed
LD A,$FE
IN A,($FE)
RRA
RET C ; C=SPACE not pressed
LD A,$07
OUT ($FE),A ; Set the border to white
LD A,$02 ; Open channel 2 (main screen)
CALL $1601
XOR A
LD ($5C3C),A ; [TV_FLAG] Signal using main screen
LD A,$16 ; Print character 'AT'
RST 10H
XOR A ; Print character '0'
RST 10H
XOR A ; Print character '0'
RST 10H
LD E,$08 ; Number of characters per colour
LD B,E ; Paper counter + 1
LD D,B ; Ink counter + 1
;; TVT_ROW
L3C34: LD A,B ; Calculate the paper colour
DEC A ; Bits 3-5 of each screen attribute
DB 0XCB
RLA ; holds the paper colour; bits 0-2
DB 0XCB
RLA ; the ink colour
DB 0XCB
RLA
ADD A,D ; Add the ink colour
DEC A
LD ($5C8F),A ; [ATTR_T] Store as temporary attribute value
LD HL,L3C8F ; TVT_DATA Point to the 'year' data
LD C,E ; Get number of characters to print
;; TVT_YEAR
L3C45: LD A,(HL) ; Fetch a character from the data
RST 10H ; Print it
INC HL
DEC C
JR NZ,L3C45 ; Repeat for the 8 characters
DJNZ L3C34 ; Repeat for all colours in this row
LD B,E ; Reset paper colour
DEC D ; Next ink colour
JR NZ,L3C34 ; Produce next row with new ink colour
LD HL,$4800 ; Point to 2nd third of display file
LD D,H
LD E,L
INC DE ; Point to the next display cell
XOR A
LD (HL),A ; Clear first display cell
LD BC,$0FFF
LDIR ; Clear lower 2 thirds of display file
EX DE,HL ; HL points to start of attributes file
LD DE,$5900 ; Point to 2nd third of attributes file
LD BC,$0200
LDIR ; Copy screen attributes
; Now that the display has been constructed, produce a continuous cycle of a 440Hz tone for 1 second followed by a period of silence for 1 second (actually 962ms).
DI ; Disable interrupts so that a pure tone can be generated
;; TVT_TONE
L3C68: LD DE,$0370 ; DE=twice the tone frequency in Hz
LD L,$07 ; Border colour of white
;; TVT_DURATION
L3C6D: LD BC,$0099 ; Delay for 950.4us
;; TVT_PERIOD
L3C70: DEC BC
LD A,B
OR C
JR NZ,L3C70
LD A,L
XOR $10 ; Toggle the speaker output whilst
LD L,A ; preserving the border colour
OUT ($FE),A
DEC DE ; Generate the tone for 1 second
LD A,D
OR E
JR NZ,L3C6D
; At this point the speaker is turned off, so delay for 1 second.
LD BC,$0000 ; Delay for 480.4us
;; TVT_DELAY1
L3C83: DEC BC
LD A,B
OR C
JR NZ,L3C83
;; TVT_DELAY2
L3C88: DEC BC ; Delay for 480.4us
LD A,B
OR C
JR NZ,L3C88
JR L3C68 ; Repeat the tone cycle
;; TVT_DATA
L3C8F: DB $13, $00 ; Bright, off
DB $31, $39 ; '1', '9'
DB $13, $01 ; Bright, on
DB $38, $36 ; '8', '6'
RST8_CMP EX (SP),HL ;HL
PUSH AF ;AF
LD A,(HL)
CP _AY_PRN_INIT
JR NC,RST8_YES
RST8_NO POP AF
EX (SP),HL
LD HL,($5C5D)
LD ($5C5F),HL
JP L0053
RST8_YES CP _AY_PRN_INIT+0X40
JR NC,RST8_NO
CP 0X73
JR NC,RST8_NO
PUSH BC ;BC
LD A,R
JP PE,RST8YES1
LD A,R
RST8YES1 DI
PUSH AF ;RF
PUSH HL ;ADR_RET
PUSH DE ;RAMNROM+DOS7FFD
LD BC,RD_1WINA0
IN H,(C)
IN A,(PEVO_CONF)
LD L,A
OR 1
OUT (PEVO_CONF),A
LD B,HIGH (RD_DOS7FFD)
IN E,(C)
DEC B
IN D,(C)
LD BC,WIN_A0
LD A,3
OUT (C),A
LD B,HIGH (WIN_P0)
XOR A
JP ADR_SEL_ROM
DUPL ADR_RST8END-$,0
RST8_END LD A,L
OUT (PEVO_CONF),A
POP DE
POP HL
POP AF
JP PO,RST8END1
EI
RST8END1 POP BC
POP AF
EX (SP),HL
RET
; ------
; UNUSED
; ------
DUPL 0X3D00-$,0
; -------------------------------
; THE 'ZX SPECTRUM CHARACTER SET'
; -------------------------------
;; char-set
; $20 - Character: ' ' CHR$(32)
CHARS binclude shr_3d00.bin