1. A system that converts alternating current from a wall outlet into the direct currents required by electronic circuits.

A computer power supply converts alternating current into multiple direct current voltages; for example, twelve volts is commonly used for drives, while 3.3 volts and 5 volts are used by the chips and other motherboard components.

2. A device used to convert, regulate, and transmit external power for use by the components housed inside a computer chassis.