The calculator automatically turns off after about 7 minutes if no key is pressed. +/- key - Press to change the displayed number from positive {+) to negative (-) or from negative (-) to positive {+). - appears when the value is negative. CE key - Press CE to delete the displayed number without losing any pending calculation. If a result is too large to show on the display, the calculator stops and displays E. Press CE to resume calculating. Press ON/AC to clear the entire calculation. Press