The keypad sets the clock/calendar and manipulates the calculator function. The alarm function is especially useful. It can be set as a clock alarm (anytime over 24 hours) or as a schedule alarm (on a selected date at a selected time). In either case, when the alarm sounds, the screen will also display a message keyed in--perfect as a reminder for, say, a dentist appointment. A 10-year lithium battery (included) powers the unit, and an automatic shutoff preserves the battery if the on/off button is not pushed after a couple of minutes. --Fred Brack