Basic Input/Output System


basic input/output system

[′in‚put ′au̇t‚pu̇t ‚sis·təm] (computer science) The part of a computer's operating system that handles communications between a program and external devices such as printers and electronic displays. Abbreviated BIOS.

Basic Input/Output System

(operating system)(BIOS, ROM BIOS) The part of the system software of the IBM PC and compatibles that provides thelowest level interface to peripheral devices and controlsthe first stage of the bootstrap process, includinginstalling the operating system. The BIOS is stored inROM, or equivalent, in every PC. Its main task is to loadand execute the operating system which is usually stored onthe computer's hard disk, but may be loaded from CD-ROM orfloppy disk at install time.

In order to provide acceptable performance (e.g. for screendisplay), some software vendors access the routines in theBIOS directly, rather than using the higher level operatingsystem calls. Thus, the BIOS in the compatible computer mustbe 100% compatible with the IBM BIOS.

As if that wasn't bad enough, many application programsbypass even the BIOS and address the screen hardware directlyjust as the BIOS does. Consequently, register levelcompatibility is required in the compatible's displayelectronics, which means that it must provide the same storagelocations and identification as the original IBM hardware.