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Length: 1152 (0x480)
Types: TextFile
Names: »MPBSUB.MAC«
└─⟦01b5c9619⟧ Bits:30005906 Microsoft Multiplan v1.05 og HELP
└─ ⟦this⟧ »MPBSUB.MAC«
; ; ; Title Multiple-Precision Binary Subtraction ; Name: MPBSUB ; ; ; Purpose: Subtract 2 arrays of binary bytes ; Minuend = minuend - subtrahend ; ; Entry: Register pair HL = Base address of minuend ; Register pair DE = Base address of minuend ; Register B = Lenght of the arrays ; ; The arrays are unsigned binary numbers with a ; maximum lenght of 255 bytes, ARRAYÆ0Å is the ; leats significant byte, and ARRAYÆLENGH-1Å ; the most significant byte. ; ; Exit: Minuend := minuend - subtrahend ; ; Registers used: AF,B,DE,HL ; ; Time: 46 cycles per byte plus 22 cycles overhead ; ; Size: Program 12 bytes ; ; MPBSUB: ;Clear carry, exit if array lenght is 0 ld a,b and a ;Clear carry, test accumulator ret z ;Return if lenght = zero ex de,hl ; so HL points to subtrahend loop: ld a,(de) ;Get next byte of minuend sbc a,(hl) ;Subtract bytes ld (de),a ;Store difference inc de ;Increment minuend pointer inc hl ;Increment subtrahend pointer djnz loop ;Continue until counter = 0 ret «eof»