NASM Coding: Basics - Examples

• msg db "Hello", 0

  In the code line above, we define a variable named

  msg

  whose content is the string literal

  Hello

  followed by the null character (

  0

  ) whose purpose is to act as the string's endpoint. The directive (= pseudo-instruction)

  db

  tells the computer to store that data as raw 8-bit bytes in the .data section of the executable.

• buffer resb 64

  This line in the .bss section declares a variable with the name

  buffer

  , and tells the computer to reserve

  64

  bytes of space for it using the

  resb

  directive, whose purpose is to "Reserve Byte(s)".

• mov rax, 1

  Here, we copy the number

  1

  into the

  rax

  64-bit register in the CPU using the

  mov

  instruction, which you will find in the .text section.