Instruction Set
<x> is a 4-bit memory address
0000 -- NOP (Do nothing)
0001 <x> -- LOAD value at <x> to ACC
0010 <x> -- STORE value in ACC at <x>
0011 <x> -- ADD value at <x> to ACC
0100 <x> -- SUB value at <x> from ACC
0101 <x> -- MUL ACC by value at <x>
0110 <x> -- DIV ACC by value at <x>
1000 <x> -- PRINT <x> to Monitor
1001 <x> -- INPUT keyboard to <x>