The Full form of BIOS is Basic Input Output System. BIOS is a built-in software in a computer. It is the first software which is run by the computer system when we turn on our computer. This software is usually stored in ROM (Read Only Memory) and located on the motherboard. In modern computer systems, the BIOS uses flash memory to store the contents. It is impossible for a computer system to continue without BIOS as it is the BIOS that loads the drivers of the hard disk and primary portions of the operating system like FAT, MBR, GPT etc, into the memory to enable the operating system to continue loading itself.

It is also known as PC BIOS, System BIOS, ROM BIOS, etc. BIOS was first appeared in 1975 in the CP/M operating system and the term was invented by Gary Kildall. The main function of BIOS is to start the computer system and to test all hardware components attach to the computer and load the operating system part. BIOS facilitates the operating system and application programs to interact with the display, keyboard and other Input/Output devices. BIOS initialize registers and handles the power management. BIOS initializes the sequence of Bootstrap and specifies the Bootable devices.