CODEWITHSUNDEEP
assemblynasm
N.D.H.
N.D.H.

Reputation: 23

What is wrong with this NASM assembly adder?

I have recently started to get into assembly, and I have been using NASM because I can easily find tutorials. Because of its difficulty, I decided I would start very small, by making a program to add 1 and 3 and output 4. I have worked it out enough that I do not receive error or warning messages, but it does not output anything aside from sh-4.3$.

segment .text
    global _start
_start:
    mov eax, '1'
    sub eax, '0'

    mov ecx, '3'
    sub ecx, '0'

    add ecx, eax
    add ecx, '0'

    mov edx, 1
    mov ebx, 1
    mov eax, 4
    int 0x80

    mov eax, 1
    int 0x80

Upvotes: 0

Views: 213

Answers (1)

Jose Manuel Abarca Rodríguez
Jose Manuel Abarca Rodríguez

Reputation: 10381

Move your result into a variable, then you display the variable :

section .data
    result : db ' ',10          ◄■■ VARIABLE
segment .text
    global _start
_start:
    mov eax, '1'
    sub eax, '0'

    mov ecx, '3'
    sub ecx, '0'

    add ecx, eax
    add ecx, '0'
    mov [result], cl          ◄■■ MOVE RESULT INTO THE VARIABLE.

    mov ecx, result           ◄■■ DISPLAY THIS VARIABLE.
    mov edx, 1
    mov ebx, 1
    mov eax, 4
    int 0x80

    mov eax, 1
    int 0x80

You have to store the address of the variable in ECX, not the value itself.

Upvotes: 1

Related Questions