A power supply is installed in the back corner of the PC case, next to the motherboard.
It converts 120vac (standard house power) into DC voltages that are used by other components in the PC.
A 20 conductor cable carries +5vdc, -5vdc +12vdc, -12vdc and ground to the motherboard.
Another pair of cables, each with four conductors and two 4-pin connectors daisy-chained along it, carry +5vdc, +12vdc and ground to the drives (hard, floppy and CD/DVD).
Typical PC power supplies are rated at 200-250 watts and sell for about $50 - $75. Higher wattage supplies are available.
