NASM Coding: Basics

The rest of these lecture notes will teach us some basic coding skills in NASM. Specifically, since the online NASM compiler that we introduced on slide 11 supports NASM x86_64 on Linux, our slides will focus on code examples that run on a x86_64 Linux device only.

In Linux x86_64 NASM programs:

• We directly interact with CPU registers: an instruction will include the name of a register (or registers) and what data we want to put inside it (or read from it).
• We request the operating system to perform services for us, such as reading or writing from files, using the

  syscall

  instruction ("system call").
• We don't import any libraries and don't call any library functions. If needed, we write our repetitively-called code.

In short, a NASM program consists of (1) data, (2) instructions, and a defined entry point into the program (

_start

).