Start64!Today we'll look at integer data types, bits, bytes, words and all that. We'll also look at the general purpose register set. I didn't really mention it in the tute but the suffixes for AT&T that match the register sizes are (using RAX as the example register):

B for AL and AH
W for AX
L for EAX
Q for RAX

Linux x64 Assembly Tutorial 2: Bits, Bytes and Registers - YouTube