What do the dollar ($) and percentage (%) signs represent in x86 assembly?

Question

I am trying to understand how the assembly language works for a micro-computer architecture class, and I keep facing different syntaxes in examples:

sub $48,         


        

Answer 1

Thats not Intel syntax, its AT&T syntax, also called GAS syntax.

the $ prefix is for immediates (constants), and the % prefix is for registers (they are required¹).

For more about AT&T syntax, see also the [att] tag wiki.

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¹ Unless the noprefix option is specified, see here & here. But usually noprefix is only used with .intel_syntax noprefix, to get MASM-like syntax.