BIOS or Basic Input/Output System is the first program accessed by the processor during start up to make sure that all the other basic programs, hard drives, ports, peripherals and the central processing unit are in good working condition. BIOS is dissimilar from the computer's operating system. The operating system resides in the hard drive and gives the user interface that can be seen on the screen after start up. The BIOS program, on the other hand, can be found right in a flash memory chip or ROM located in the motherboard. It is the basic necessity for booting a computer.
BIOS have various functions in a computer but its most important task is to load the operating system. BIOS gives the microprocessor its first instructions upon activating the computer. The instructions of the BIOS to the microprocessor during start up are the following: power on self test which tests the operating status of all the hardware in the computer, activation of other BIOS chips in some other computer mechanism like SCSI and graphics cards, checking and management of computer peripherals by low level routines during the start-up process, and management of clock, hard drive and other settings.