Multiplying and Dividing on the 6502 #VintageComputing
The MOS 6502 was the first affordable microprocessor and used in many early computers including the Apple II and Commodore 64. But this silicon was not that complex – there are no general multiply and divide instructions!
One of the more common questions asked by new 6502 programmers seems to be, “Hey…there’s no multiply instruction! How do I multiply on the 6502?” This article presents some answers to this question, and as a bonus, answers to the companion question, “How do I divide on the 6502?”
Of course the methods shown are not the only ways to multiply and divide, nor even the fastest. They are, however, probably the easiest ways to understand.
Most of the routines are for unsigned integers, since these are the easiest kinds of numbers to work with. Extending them to signed integers is discussed briefly near the end.
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