NASM - The Netwide Assembler

NASM Forum => Programming with NASM => Topic started by: maplesirop on April 18, 2013, 09:14:42 PM

Title: How can we distinguish direct addressing from register indirect addressing?
Post by: maplesirop on April 18, 2013, 09:14:42 PM

This is register indirect addressing:

mov eax, [edx]

and this is direct addressing

mov AL, [label1]

how do we distinguish them?

I thought [var] meant access the address instead of the value...

Do base and base indexed addressing work like register indirect addressing (by accessing the address instead of the value)?

Title: Re: How can we distinguish direct addressing from register indirect addressing?
Post by: Frank Kotler on April 18, 2013, 10:14:47 PM

"[var]" refers to the value at address "var".

Code: [Select]

section .data
    var dd 42
    array dd 10, 20, 30, 40

section .text
    mov eax, [var] ; 42 in eax
    mov eax, var ; 0x8049123 (or so) in eax
    mov eax, array ; address
    mov ebx, 2 ; element to get (counting from 0)
    mov eax, [eax + ebx * 4] ; 30 in eax
Something like that...

Best,
Frank