Registers

An x86-64 CPU has sixteen 64-bit "general purpose" registers. The registers have aliases that translate back to their legacy 32-bit and 16-bit names.

64-bit Low 8 bit RAX EAX AX AL RBX EBX BX BL RCX ECX CX CL RDX EDX DX DL RSI ESI SI RDI EDI DI RBP EBP BP RSP ESP SP R9 R9D R9W R10 R10D R10W R11 R11D R11W R12 R12D R12W R13 R13D R13W R14 R14D R14W R15 R15D R15W

There are also 2 special purpose registers:

RIP EIP IP RFLAGS EFLAGS FLAGS