As an electrical device, the computer needs power in order for its components to operate properly. The device responsible for supplying power to the computer is the power supply. In a short way, we could say that the main function of the power supply is to convert alternating voltage (a.k.a. AC) which is supplied by the electrical power system into continuous voltage (a.k.a. DC). In other words, the power supply converts the conventional 110V or 220V alternating voltage into continuous voltage used by the PC electronic components, which are: +3,3V, +5V, +12V, -5V and -12V. The power supply is also present in the PC cooling process, facilitating the airflow inside the case.