ex2.asm

global _start ; entry point

section .data: ; variables
    msg db "Hello world!", 0x0a ; 0x0a is the \n char (newline)
    len equ $ - msg ; string length

section .text:
_start:
    mov eax, 4   ; sys_write system call
    mov ebx, 1   ; stdout file descriptor
    mov ecx, msg ; bytes to write
    mov edx, len ; number of bytes to write
    int 0x80     ; perform system call
    mov eax, 1   ; sys_exit system call
    mov ebx, 0   ; exit status is 0
    int 0x80     ; perform system call