* bit1 - 1 (Fixed)
* bit0 - CF - Carry Flag
|| AC is used for BCD arithmetic (DAA instruction). Often paired with A as The accumulator and the flags together are called the 16-bit Program Status Word (PSW), or program status word. PSW can be pushed to or popped from the stack.
|-
| SP (Stack Pointer) || 16-bit || Points to the top of the stack || Used for PUSH, POP, CALL, RET instructions