BIOS

The BIOS (/ˈbaɪ.ɒs/, an acronym for Basic Input/Output System and also known as the System BIOS, ROM BIOS or PC BIOS) is a type of firmware used to perform hardware initialization during the booting process (power-on startup) on IBM PC compatible computers. In the days of DOS and 16-bit Windows (Windows 1-3) it also provided runtime services for operating systems and programs, however BIOS services are not used by modern multitasking operating systems (e.g. 32-bit Windows, or Windows 95 and later) after they initially load, so the importance of BIOS is greatly reduced from what it was initially. The BIOS firmware is built into personal computers (PCs), and it is the first software they run when powered on. The name itself originates from the Basic Input/Output System used in the CP/M operating system in 1975. Originally proprietary to the IBM PC, the BIOS has been reverse engineered by companies looking to create compatible systems and the interface of that original system serves as a de facto standard.