Arithmetic statements

Now we will look at different C statements and how they are represented in the assembly. We will take Intel IA-32 as an example and the same concept applies to other assembly languages as well:

• X = 50 (assuming 0x00010000 is the address of the X variable in memory):

mov eax, 50
 mov dword ptr [00010000h],eax

• X = Y+50 (assuming 0x00010000 represents X and 0x00020000 represents Y):
  

mov eax, dword ptr [00020000h]
add eax, 50
mov dword ptr [00010000h],eax

• X = Y + (50 * 2):
  

mov eax, dword ptr [00020000h]
 push eax ;save Y for now
 mov eax, 50 ;do the multiplication first
 mov ebx,2
 imul ebx ;the result is in edx:eax
 mov ecx, eax
 pop eax ;gets back Y value
 add eax,ecx
 mov dword ptr [00010000h],eax
 

• X = Y + (50 / 2):
  

mov eax, dword ptr [00020000h]
 push eax ;save Y for now
 mov eax, 50
 mov ebx,2
 div ebx ;the result in eax, and the remainder is in edx
 mov ecx, eax
 pop eax
 add eax,ecx
 mov dword ptr [00010000h],eax
 

• X = Y + (50 % 2) (% represents the remainder):

mov eax...