declare register AR(15:0), DR(19:0), SP(15:0), PC(15:0);
declare memory MEM(AR,DR);
INIT:	PC <- 0, AR <- 0, SP <- $FFFF, DR <- 0;
FETCH:	AR <- PC;
	read MEM, PC <- PC + 1 |
		switch DR(19:16) { case 0: goto PUSH
			case 1: goto POP
			case 2: goto SUB
			case 3: goto NOT
			case 4: goto JNZ
			default: goto FETCH };
PUSH:	AR <- DR(15:0), SP <- SP - 1;
	read MEM, AR <- SP;
	write MEM | goto FETCH;
POP:	AR <- SP, if SP <> $FFFF then SP <- SP + 1 fi;
	read MEM, AR <- DR(15:0);
	write MEM | goto FETCH;
SUB:	AR <- SP, SP <- SP + 1;
	read MEM, AR <- SP;
	AR <- DR(15:0), read MEM;
	AR <- AR - DR(15:0);
	DR(15:0) <- AR, AR <- SP;
	write MEM | goto FETCH;
NOT:	AR <- SP;
	read MEM;
	AR <- not DR(15:0);
	DR(15:0) <- AR, AR <- SP;
	write MEM | goto FETCH;
JNZ:	AR <- SP, SP <- SP + 1;
	read MEM;
	if DR(15:0) <> 0 then goto JNZ1 fi;
	SP <- SP + 1 | goto FETCH;
JNZ1:	AR <- SP, SP <- SP + 1;
	read MEM;
	PC <- DR(15:0) | goto FETCH;