Back to General and Gameplay Programming

32 bit add in ASM

General and Gameplay Programming Programming

Started by Sante05 May 04, 2007 07:06 AM

1 comment, last by Sante05 16 years, 11 months ago

Sante05

190

Author

May 04, 2007 07:06 AM

Hi, I'm having some problems when adding 2 32-bit registers in ASM (using VC++ 6.0):


mov eax, 2
mov ebx, 4886718345
add eax, ebx

When doing this, the eax register returns with 591751051 instead of the correct result (4886718347). It seems it's only adding the lower 16 bits. (Note: the numbers are in decimal)

-----DevZing Blog (in Spanish)

d00fus

328

May 04, 2007 07:18 AM

This is because 4886718345 is out of the range of a 32-bit unsigned int. If you modulo this with 2^32 you get 591751049 which when added to 2 gives you the result you are getting.