NASM Coding: Basics

A NASM program is divided into sections:

section .data      ; initialized data
    ...
section .bss       ; uninitialized data
    ...
section .text      ; code
    global _start
    ...

• The data section contains variables that are initialized (= were assigned some initial values.)
• The bss (= block started by symbol) section contains variables that weren't yet initialized; this is basically just memory reservation for later use.
• The text section contains the instructions of the program. The computer starts running the code at a label named

  _start

  .