instructions
a -- a--
DEC -> Decrements the top byte on the stack by 1
DECw -> Decrements the top word on the stack by 1
DECx -> Decrements x by 1
DECxw -> Decrements xw by 1
DECy -> Decrements y by 1
DECyw -> Decrements yw by 1
DECxy -> Decrements x and y by 1
DECxyw -> Decrements xw and yw by 1