Question

I have a basic question about assembly.

Why do we bother doing arithmetic operations only on registers if they can work on memory as well?

For example both of the following cause (essentially) the same value to be calculated as an answer:

Snippet 1

.data
    var dd 00000400h

.code

    Start:
        add var,0000000Bh
        mov eax,var
        ;breakpoint: var = 00000B04
    End Start

Snippet 2

.code

    Start:
        mov eax,00000400h
        add eax,0000000bh
        ;breakpoint: eax = 0000040B
    End Start

From what I can see most texts and tutorials do arithmetic operations mostly on registers. Is it just faster to work with registers?

Answer 1

Registers are much faster and also the operations that you can perform directly on memory are far more limited.