how to write code if right most bit is equal to 1?

[ramguru]

I guess "then" means after all iterations, and EBX should be 0, EAX something big, ECX - product (result). This means that you really miswrite ...

[EduardoS]

His code is ok, just don't preserve the registers,
To preserve registers i prefer push/pop, if not possible then save to somewhere in memory if not possible too you need to make another proc...
With loops there is one way (i mean, one way better than add eax to ecx ebx times) to do it modifying only two registers (the counter and the result), without loop you just need to modify the result, now think how to do it, it's your homework not mine :8)

[MichaelW]

FWIW the Irvine32 library with full source code is available (apparently from the author) here:

http://www.nuvisionmiami.com/books/asm/examples/index.htm

It is a beta version, but the DumpRegs procedure and the macros it depends on are essentially unchanged from the earlier non-beta version.

[dsouza123]

Code Select Expand


.data
  holdeax dd 0
  holdebx dd 0

.code
  mov eax, 5
  mov ebx, 6
  mov ecx, 0

  mov holdeax, eax  ; store starting values of eax and ebx for later
  mov holdebx, ebx

  cmp ebx, 0
  jz  iszero
again:
    test ebx, 1
    jz  skip
    add ecx, eax
skip:
    shl eax, 1
    shr ebx, 1
    jnz again
iszero:
  mov eax, holdeax  ; restore starting eax and ebx
  mov ebx, holdebx
  ; ecx has the part of the answer that fits in one dword


[scooter4483]

yeah, the teacher said i could push and pop onto edi and esi.  how do implement that?  thanks.

[EduardoS]

To save in edi and esi simple mov:

mov edi, eax
mov esi, ebx
...
...
...
mov eax, edi
mov ebx, esi

[BogdanOntanu]

And take care: the rules here state that we do not make other people's homework:D