Question

I have written following assembly code for adding 10 numbers.I am able to compile it and execute it but I am getting wrong result.
I just wanted to know how do I print the value of total on scree.

section .data
num1: dw 10, 20, 30, 40, 50, 10, 20, 30, 40, 50
total: dw 0
msg :  db "sum=%d",10,0

section .text
    extern _printf
    global _main
_main:
    push ebp
    mov ebp,esp
    mov ebx,num1 ;point bx to first number
    mov ecx,10      ;load count of numbers in ecx
    mov eax,0       ;initialize sum to zero
loop:
    add eax,[ebx]
    add ebx,2
    sub ecx,1
    jnz loop
    mov [total],eax

    push total
    push msg
    call _printf

    pop ebp
    mov esp,ebp
    ret

solution

section .data
num1: dd 10, 20, 30, 40, 50, 10, 20, 30, 40, 50,300
total: dd 0
msg :  dd "sum=%d",10,0

    section .text
        extern _printf
        global _main
    _main:
        push ebp
        mov ebp,esp
        mov ebx,num1 ;point bx to first number
        mov ecx,11     ;load count of numbers in ecx
        mov eax,0       ;initialize sum to zero
    loop:
        add eax,[ebx]
        add ebx,4
        sub ecx,1
        jnz loop
        mov  [total],eax
        push dword [total]

        push msg
        call _printf
        mov esp,ebp
        pop ebp

        ret

Answer 1

I see a couple of issues here. First, you’ve got num1 and total declared as dw. dw may sound like it means “dword”, but it means “data word”. You want these to be dd – “data dword”… since that’s how you’re using them. (and add ebx, 4 not 2) If you really need to use word (16-bit) values in 32-bit code, it can be done, but is awkward.

The second problem I see is that push total before your call _printf pushes the address of total. You want the “[contents]” of memory here, so push dword [total]. (push msg is correct)

After this, you probably want add esp, 8 (I like to write it as add esp, 4 * 2 – two parameters of 4 bytes each). It is possible to “defer” this stack cleanup – mov esp, ebp will fix you up, but it needs to be done BEFORE the pop ebp!!!

… there may be more…