64 bit - How to do 64 bit multiply on 16 bit machine?

Question

I have an embedded 16 bit CPU. On this machine ints are 16 bit wide and it supports longs that are 32 bits wide. I need to do some multiplications that will need to be stored in 64 bits (e.g. multiply a 32 bit number by a 16 bit number). How can I do that with the given constraints? I do not have a math library to do this.

Answer 1

You might want to check out Hacker's Delight (it's a book and a website). They have C implementations of Knuth's signed multiword multiplication and unsigned multiword multiplication from The Art of Computer Programming Vol.2.