Assembly Language for Beginners

1.20. ARRAYS

1.20.1 Simple example

#include <stdio.h>

int main()
{
int a[20];
int i;

for (i=0; i<20; i++)

a[i]=i*2;

for (i=0; i<20; i++)

printf ("a[%d]=%d\n", i, a[i]);

return 0;
};

x86

MSVC

Let’s compile:

Listing 1.224: MSVC 2008

_TEXT SEGMENT
_i$ = -84 ; size = 4
_a$ = -80 ; size = 80
_main PROC
push ebp
mov ebp, esp
sub esp, 84 ; 00000054H
mov DWORD PTR _i$[ebp], 0
jmp SHORT $LN6@main
$LN5@main:
mov eax, DWORD PTR _i$[ebp]
add eax, 1
mov DWORD PTR _i$[ebp], eax
$LN6@main:
cmp DWORD PTR _i$[ebp], 20 ; 00000014H
jge SHORT $LN4@main
mov ecx, DWORD PTR _i$[ebp]
shl ecx, 1
mov edx, DWORD PTR _i$[ebp]
mov DWORD PTR _a$[ebp+edx4], ecx
jmp SHORT $LN5@main
$LN4@main:
mov DWORD PTR _i$[ebp], 0
jmp SHORT $LN3@main
$LN2@main:
mov eax, DWORD PTR _i$[ebp]
add eax, 1
mov DWORD PTR _i$[ebp], eax
$LN3@main:
cmp DWORD PTR _i$[ebp], 20 ; 00000014H
jge SHORT $LN1@main
mov ecx, DWORD PTR _i$[ebp]
mov edx, DWORD PTR _a$[ebp+ecx4]
push edx
mov eax, DWORD PTR _i$[ebp]
push eax
push OFFSET $SG2463
call _printf
add esp, 12 ; 0000000cH
jmp SHORT $LN2@main
$LN1@main: