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I want to simply get the user to input a number. I can get input (I think), but this is a string, and I need to convert it to a number (DWORD). I couldn't find anything that worked in MASM. I tried the C functions strtol and atoi, but it couldn't find them. Is there some function that works in MASM? Or do I have to write my own conversion?

I tried several include files, but I couldn't get the C functions:
windows.inc
kernel32.inc
user32.inc
msvcrt.inc

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Its over 20 years since I used MASM so I'm a bit rusty. The algorithm is pretty straightforward though.

  • Assuming your string is in ASCII
  • Start at the end of the string
  • You will need to split each character off the string and subtract 30H from it to give the digit
  • store that digit in a register
  • calculate your next power of ten
  • Each time you move one character left and get that digit multiply by the next power of ten
  • add to accumulator

E.g for an integer

31H 32H 33H

31h-30H = 1H 32H-30H = 2H * 10 33H-30H = 3H * 10 * 10

Bingo!

If the number represents a double you will need to cope with in a similar manner.

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sooo... there's no function to do it for me?
If you want to call atoi you would need to include the C runtime libraries rather than the Windows libraries
Would that be msvcrt.lib? I tried both the .lib and the .inc, but it said undefined symbol. Maybe it is in the .lib but not the .inc, and I need to proto define it.
Ok, I went atoi PROTO C strptr:DWORD and includelib'ed msvcrt.lib and it worked!
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I did atoi PROTO C strptr:DWORD and then I was able to call atoi.

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