In computing, BIOS (/ˈbaɪɒs, -oʊs/, BY-oss, -ohss; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is a type of firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process (power-on startup). On a computer using BIOS firmware, the firmware comes pre-installed on the computer's motherboard.
The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS firmware was originally proprietary to the IBM PC; it was reverse engineered by some companies, such as Compaq, Phoenix Technologies, AMI and others, looking to create compatible systems. The interface of that original system serves as a de facto standard.