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.
The power supply is probably the most neglected component on PC. Many times, when buying a computer, we just take on account the processor clock, the motherboard model, the quantity of installed memory, the hard disk storage capacity, and we forget about the power supply, which, in fact, is the one who supplies the "fuel" for the PC parts to operate properly. A power supply of good quality and with enough capacity can increase the durability of your equipment. Just to have an idea, a high-quality power supply will cost less than 5% of the PC total amount. On the other hand, a low-quality power supply can cause several intermittent problems, which are mostly difficult to be solved. A defective or bad-intentioned power supply can lock the PC, can result in hard disk bad blocks, can result in the infamous "blue screen of death" errors and random resets and freezings, added to many others problems.
