Know how to use "fewer" and "less"? Find out.
(UPS) A battery powered power supply unit that is guaranteed to provide power to a computer in the event of interruptions in the incoming mains electrical power. Different rating UPSs will provide power for different lengths of time.
Modern UPSs connect to the computer's serial port and provide information such as battery time remaining, allowing the computer to shut down gracefully before complete loss of power.