What is the meaning of XOR in x86 assembly?

Question

I\'m getting into assembly and I keep running into xor, for example:

xor     ax, ax

Does it just clear the register\'s value?

Answer 1

If I remember correctly xor ax, ax is a one byte assembly instruction, whilst mov ax, 0 would be at least 3 and would probably take slightly longer to execute. It will certainly take longer to decode than the xor instruction.