BIOS

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. The picture below is an example of what a BIOS chip may look like on a computer motherboard. The BIOS pictured is of an early AMIBIOS, a type of BIOS manufactured by AMI.

(Above) A pair of AMD BIOS chips for a Dell 310 computer from the late 1980s

What is included in a BIOS?

The BIOS includes instructions on how to load basic computer hardware. It also 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 hear a combination of beeps indicating what is malfunctioning in the computer.

What are 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 is available 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 setup or CMOS setup - Configuration program that allows you to configure hardware settings including system settings, such as computer passwords, time, and date.

Can a BIOS chip be upgraded or updated?

Adding additional memory to a BIOS chip, as an upgrade, can only be done by replacing the existing BIOS chip with a new, more advanced BIOS chip.

The data on a BIOS chip can be updated if it's a flash BIOS. Using specially designed software, the BIOS can be updated to fix problems or add new features for the motherboard.