What is BIOS?

A BIOS (Basic Input/Output System) is an electronic set of instructions stored in EPROM and used by the CPU to perform start-up procedures when the computer is turned on. It  is located on the chip inside of  the computer and is designed in such a  way that protects it from disk failure.

There are two main function of  BIOS: One to determine what computer peripheral devices (keyboard, mouse, disk drives, printers, video cards, etc.) are available and second to load the operating system (OS) onto the main memory. As the computer  started BIOS  gives the instructions for the POST (Power-On-Self-Test). This self test ensures that all the required computer peripheral devices are attached in the right way and all the necessary  functionality parts are working  correctly.  if  BIOS detects any sort of errors during POST, it  instructs the computer to give a code that reveals the problem. The sound of  beeps begin to ring  in a series to indicate the errors. 

Besides these the BIOS also instruct the users how to interact with some critical components like drives and memory, by  giving basic information  necessary for loading  the operating system. BIOS  allows the users to make some certain adjustments in itself  through a configuration screen on the computer. As soon as, the system turn on, the user can access the setup screen  through using a special key sequences. The users can change in the order  in which drives are accessed during startup and controlling functionality of a number of critical devices. The Features of  BIOS versions may vary to the personnel computer system.