What is BIOS (Basic Input/Output System)

BIOS may refer to any of the following:

1. Short for Basic Input/Output System, the BIOS (pronounced bye-oss) is a ROM chip found on motherboards that allows you to access and set up your computer system at the most basic level. In the picture below, is an example of what a BIOS chip may look like on your computer motherboard. In this example, this is a picture of an early AMIBIOS, a type of BIOS manufactured by the AMI. Another good example of a BIOS manufacturer is Phoenix.

The BIOS includes instructions on how to load basic computer hardware and includes a test referred to as a POST (Power On Self Test) that helps verify the computer meets requirements to boot up properly. If the computer does not pass the POST, you will receive a combination of beeps indicating what is malfunctioning within the computer.

The four main functions of a PC BIOS

• POST - Test the computer hardware and make sure no errors exist before loading the operating system. Additional information on the POST can be found on our POST and Beep Codes page.
• Bootstrap Loader - Locate the operating system. If a capable operating system is located, the BIOS will pass control to it.
• BIOS drivers - Low level drivers that give the computer basic operational control over your computer's hardware.
• BIOS or CMOS Setup - Configuration program that allows you to configure hardware settings including system settings such as computer passwords, time, and date.

Related pages

• How to enter the BIOS or CMOS setup.
• How to enter BIOS or CMOS setup without using a keyboard.
• Additional information and help with BIOS updates.
• How to clear an unknown BIOS or CMOS password.
• What is the difference between BIOS and CMOS?
• Listing of computer BIOS manufacturers.
• Computer BIOS help and support.

2. When referring to a person BIO, BIO's is short for biography and is a term used to describe a brief description of a person. A short biography or description of people who have affected the computer industry can be found on our computer people section.

ACPI, BBS, BIO, BIOS shadow, BPB, CMOS, EFI, Firmware, Flash BIOS, FWH, Libreboot, Motherboard terms, NVRAM, PROM, UEFI

Last Reviewed: 11-Jul-2017

Article ID: 000005476

The BIOS setup program can be used to view and change the BIOS settings for the computer. To access the settings, press the F2 key after the Power-On Self-Test (POST) memory test begins and before the operating system boot starts.

If any problems occur after making BIOS setting changes (poor performance or intermittent issues), reset the desktop board to default values with these steps:

1. During boot, enter the BIOS setup by pressing F2.
2. Press F9 to set defaults.
3. Press F10 to save and exit.

If the system locks or will not boot after making BIOS settings changes, start a BIOS recovery as described in the Instructions for Recovery BIOS update.

BIOS Settings Glossary Version 19 (PDF) 
The latest BIOS settings glossary is version 19 and includes the BIOS settings for the currently shipping desktop boards.

File name: BIOSGlossary_v19.pdf
Size: 307 KB
Date: November 2012
Version: 19

Note: PDF files require Adobe Acrobat Reader*

Version 13

Version 13 of the BIOS settings glossary is an archived glossary that includes settings for discontinued and legacy desktop boards.