What is BIOS (Basic Input/Output System)

Short for Basic Input/Output System, the BIOS, ROM BIOS, or System BIOS is a chip located on all motherboards that contain instructions and setup for how your system should boot and how it operates. In the below picture, 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.

4 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.