Assembly Help

[ChAoTiCpInOy]

I'm trying to write a program to multiple two 10 digit numbers using arrays in MASM. I have no idea where to start. I can do like adding in the arrays, but nothing like multiplication.

 

[esun]

Hmm, okay, well if you can do addition, surely you can do multiplication, since n * m = n + n + ... + n (m times). So write a loop (which you should know how to do in MASM) and run your addition code in that loop.

 

[Cogman]

Hmm, okay, well if you can do addition, surely you can do multiplication, since n * m = n + n + ... + n (m times). So write a loop (which you should know how to do in MASM) and run your addition code in that loop.

That is EXTREMELY slow. Given that he is using masm, I'm going to assume that this is the x86 architecture. With that in mind, there is a multiplication instruction.

http://faydoc.tripod.com/cpu/imul.htm
http://faydoc.tripod.com/cpu/mul.htm

*edit*Err um, ignore the above, I just realized what he meant by multiplying ten digit numbers

Barring that, the RPN is an extremely fast and easy to implement algorithm that only uses bitshifts and addition. (dividing by two is a bitshift left.) It isn't the fastest algorithm, but it isn't fast enough for most applications.
http://mathforum.org/dr.math/faq/faq.peasant.html

As for IO, use the C standard io library. There is no reason to write your own.

 

[Schmide]

I guess the issue you're running into is you have ascii numbers and want to do floating point math. In a c/c++ env you would use atof() or so to convert to a double and then use the floating point unit.

If you are so inclined you're going to have to write your own ascii to float and float to ascii or do a very large cross multiply.