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Length: 2560 (0xa00)
Types: TextFile
Names: »DEC2BN.MAC«
└─⟦01b5c9619⟧ Bits:30005906 Microsoft Multiplan v1.05 og HELP
└─ ⟦this⟧ »DEC2BN.MAC«
; ; ; ; ; Title Decimal ASCII to binary ; Name: DEC2BN ; ; ; ; Purpose: Convert ASCII characters to two byte of binary ; data ; ; Entry: HL = Base address of input buffer ; ; Exit: HL = Binary value ; if no errors then ; carry = 0 ; else ; carry = 1 ; ; Registers used: AF,BC,DE,HL ; ; Time: Approximately 152 cycles per byte plus ; a maximum of 186 cycles overhead ; ; Size: Program 79 bytes ; Data 1 byte ; ; ; DEC2BN: ;Initialize - save length, clear sign and value ld a,(hl) ;Save lenght in B ld b,a inc hl ;point to byte after lenght sub a ld (ngflag),a ;assume number is positive ld de,0 ;Start with value = 0 ;Check for empty buffer or b ;Is buffer lenght zero ? jr z,erexit ;Yes, exit with value = 0 ;Check for minus or plus sign in front init1: ld a,(hl) ;Get first character cp '-' ;Is it a minus sign ? jr nz,plus ;No, branch ld a,0ffh ld (ngflag),a ;Yes, make sign of number negative jr skip plus: cp '+' ;Is first character a plus sign ? jr nz,chkdig ;No, start conversion skip: inc hl ;Skip over sign byte dec b ;Decrement count jr z,erexit ;Error exit if only a sign in buffer ;Conversion loop ; continue until the buffer is empty ; or a non-numeric character is found cnvert: ld a,(hl) ;Get next character chkdig: sub '0' jr c,erexit ;Error if <'0' (Not a digit) cp 9+1 jr nc,erexit ;Error if >'9' (Not a digit) ld c,a ;Character is digit, save it ;Valid decimal digit so ; value *= value *10 ; = value * (8+2) ; = (value * 8) + (value * 2) push hl ;Save buffer pointer ex de,hl ;HL = value add hl,hl ; * 2 ld e,l ;save times 2 in DE ld d,h add hl,hl ; * 4 add hl,hl ; * 8 add hl,de ;Value = value * (8*2) ;Add in the next digit ; value := value + digit ld e,c ;Move next digit to E ld d,0 ; high byte is 0 add hl,de ;Add digit to value ex de,hl ;DE = value pop hl ;Point to next character inc hl djnz cnvert ;Continue conversion ;Conversion is complete, check sign ex de,hl ;HL = value ld a,(ngflag) or a jr z,okexit ;Jump if the value was positive ex de,hl ;Else replace value with -value ld hl,0 or a ;Clear carry sbc hl,de ;Subtract value from 0 ;No errors, exit with carry clear okexit: or a ;Clear carry ret ;An error, exit with carry set erexit: ex de,hl ;HL = value scf ;Set carry ret ;DATA ngflag: ds 1 ;Sign of number «eof»