BIOS

In IBM PC compatible computers, the basic input/output system (BIOS), also known as the System BIOS or ROM BIOS (pronounced /ˈbaɪ.oʊs/), is a de facto standard defining a firmware interface.

The BIOS software is built into the PC, and is the first code run by a PC when powered on ('boot firmware'). The primary function of the BIOS is to set up the hardware and load and start an operating system.