Hello World Assembly Programming

; Macros used in NASM assembler
%define SYS_EXIT    1
%define SYS_READ    3
%define SYS_WRITE   4
%define STDOUT      1
%define STATUS      0
%define SYS_INTR    0x80

section .data
    hello: db 'Hello World!', 10 ;NOTE This 10 is for new line
    ;hello: db 'Hello World!'
    helloLen: equ $-hello           ;This will have the length of helloLen
                                    ; Note unlike "hello", helloLen is not an address; but value

section .text
    global _start

_start:
        ;Printing Hello World String.
        mov eax, SYS_WRITE
        mov ebx, STDOUT
        mov ecx, hello
        mov edx, helloLen
        int SYS_INTR

        ;Exit from main program
        mov eax, 1
        mov ebx, 0
        int SYS_INTR
        ret                 ; This will not get executed at all

Command to Assemble:

nasm -f elf hello.asm

Command to Link:

ld -s -o hello hello.o -m elf_i386 (Note elf_i386 denotes that this needs to be linked for 32 bit application)