The basic input/output system (BIOS), also known as the System BIOS is a de facto standard defining a firmware interface. The BIOS software is the first code run by a PC when booting up. The primary function is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware and start the operating system.

BIOS software is stored on a non-volatile ROM chip built into the system on the mother board. In modern computer systems, the BIOS chip's contents can be rewritten allowing BIOS software to be upgraded.

BIOS help configure the computer
to set the system clock
to enable or disable system components
to select the boot device order
set password for BIOS UI