- Basic Input/Output System.
The BIOS provides an interface between a computer's operating system and the computer's hardware. Unlike the operating system the BIOS is built into the computer and thus is always available. Many computers hold the BIOS in Flash and allow it to be upgraded.
The BIOS will normally perform various diagnostic tests straight after power-up (see POST). At this point it is usual for a BIOS to allow you to enter a "BIOS Screen" to configure aspects of the BIOS (not every BIOS supports this).
Each BIOS may have a different way of invoking its "BIOS Screen" and the correct method should be stated in the manual. It is commonly (although not always) displayed on the screen during the BIOS part of the start-up. The following individual keys are commonly used to invoke the BIOS screen: DEL, F1, F2 or F10.