private int unaryExecute(int i) {
		switch(sim40.memory[i]) {

		/* Unary Instructions */
		case 4: /* cclear */
			switchOffFlag(2);
			break;

		case 5: /* cset */
			switchOnFlag(2);
			break;

		case 6: /* xinc */
			sim40.memory[Simulator.XREG_ADDRESS]++;
			checkResetOverflow(Simulator.XREG_ADDRESS);
			break;

		case 7: /* xdec */
			sim40.memory[Simulator.XREG_ADDRESS]--;
			checkResetUnderflow(Simulator.YREG_ADDRESS);
			break;

		case 8: /* yinc */
			sim40.memory[Simulator.YREG_ADDRESS]++;
			checkResetOverflow(Simulator.YREG_ADDRESS);
			break;

		case 9: /* ydec */
			sim40.memory[Simulator.YREG_ADDRESS]--;
			checkResetUnderflow(Simulator.YREG_ADDRESS);
			break;

		}

		return ++i;
	}