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Length: 1280 (0x500)
Types: TextFile
Names: »MUL16.MAC«
└─⟦01b5c9619⟧ Bits:30005906 Microsoft Multiplan v1.05 og HELP
└─ ⟦this⟧ »MUL16.MAC«
; ; ; Title 16-bit Multiplication ; Name: MUL16 ; ; ; Purpose: Multiply 2 signed or unsigned 16-bit words and ; return a 16-bit signed or unsigned product ; ; Answers needing more than 16 bits: bits higher ; than 15 are lost ; ; Entry: Register HL = Multiplicand ; Register DE = Mulitplier ; ; Exit: Product = multiplicand * mulitplier ; Register HL = product ; ; Registers used: AF,BC,DE,HL ; ; Time: Approximately 865 to 965 cycles ; ; Size: Program 22 bytes ; ; ; MUL16: ;Initialize partial product, bit count ld c,l ;BC = multiplier ld b,h ld hl,0 ;product = 0 ld a,15 ;count = bit lenght - 1 ;shift-and-add algorithm ; if msb of multiplier is 1, add multiplicand to partial ; product ; shift partial product, mltiplier left 1 bit mlp: sla e ;shift multiplier left 1 bit rl d jr nc,mlp1 ;Jump if multiplier = 0 add hl,bc ;Add multiplicand to partial product mlp1: add hl,hl ;shift partial product left dec a jr nz,mlp ;Continue until count = 0 ;Add multiplicand one last time if msb of multiplier is 1 or d ;Sign flag = msb of multiplier ret p ;exit if msb of multiplicand is 0 add hl,bc ;Add multiplicand to product ret «eof»