NASM Coding: Basics

We can also access smaller portions of each of the registers that we listed on the previous slide. For example, for the register 

rax
, the following parts have names:

Register Size What Part 
eax
 32-bit Lower (rightmost) 32 bits of 
rax
 
ax
 16-bit Lower (rightmost) 16 bits of 
rax
 
ah
 8-bit Higher (leftmost) 8 bits of 
ax
 
al
 8-bit Lower (rightmost) 8 bits of 
ax
Named parts of the rax register: eax, ax, ah, and al

Named parts of the rax register. Taken from Raw Linux Threads via System Calls, Public Domain.

These notes by Miriam Briskman are licensed under CC BY-NC 4.0 and based on sources.