Acronym for basic input/output system, pronounced "bye-os." In the PC, the BIOS is a set of instructions that tests the hardware when the computer is first turned on, starts to load the operating system, and lets the computer's hardware and operating system communicate with applications and peripheral devices, such as hard disks, printers, and video adapters. These instructions are stored in ROM as a permanent part of the computer.
As new hardware is developed, new BIOS routines must be created to service those devices. For example, BIOS support has been added for power management and for ever-larger hard disks. If you are experiencing problems accessing such devices after adding them to an existing system, your computer's BIOS may be out of date. Contact your computer supplier for information about BIOS updates.