instructions a b -- b a SWP -> Swaps byte b with a on the stack. SWPw -> Swaps word b with a on the stack. SWPx -> Swaps byte x with a on the stack. SWPxw -> Swaps word xw with a on the stack. SWPy -> Swaps byte y with a on the stack. SWPyw -> Swaps word yw with a on the stack. SWAPxy -> Swaps bytes x with y. SWAPxyw -> Swaps word xw with yw.