BIOS

The Basic Input Output System (BIOS) is a short piece of software that is run at the start-up of a personal computer. The BIOS is needed for the configuration of the hardware and the communication between the hardware and the operating system. The BIOS always performs a test of the hardware on start-up. This is called the power-on self test (POST).

The user is able to change the hardware configuration by pressing a special key at system start-up, usually a function key, the delete key or the escape key.