NASM Coding: Declaring Variables & Reserving Data

Reserving space for variables (in the

.bss

section:)

myarr resb 10  ; Reserve space for 10 bytes
var1 resw 2    ; Reserve space for 2 words (= 2 * 2 = 4 bytes)
large resd 5   ; Reserve space for 5 dwords (= 5 * 4 = 20 bytes)
wow resq 1;    ; Reserve space for 1 qword (= 8 bytes)

NASM has greater data types (e.g.,

reso

= 16 bytes,

resy

= 32 bytes, etc., but we won't need these for our course.) Also:

mov rbx, byte [loc]   ; Copies a single byte at RAM[loc] to rbx
mov rbx, word [loc]   ; Copies a single word (= 2 bytes) starting at RAM[loc] to rbx
mov rbx, dword [loc]  ; Copies a single dword (= 4 bytes) starting at RAM[loc] to rbx
mov rbx, qword [loc]  ; Copies a single qword (= 8 bytes) starting at RAM[loc] to rbx