Basic Input Output System

Kailash Chandra Behera | Friday, December 18, 2020


The BIOS (Basic Input Output System) provides a set of instructions and is responsible for booting the computer. It performs all the tests needed at startup time. This article provides information about BIOS, its history, and how it works.

Basic Input Output System Definition

The BIOS is the firmware(collection of program that stores in Motherboard ROM) used to perform hardware initialization during the booting process (power-on startup) and to provide runtime services for operating systems and programs. It consists of a collection of programs embedded in one or more ROM chips( The firmware was stored in a Read Only Memory (ROM) chip on the PC motherboard.).

Getting Started

The BIOS is the program used by microprocessor of a computer to start it's system after it is powered on. It's main responsiblity is to manage data flow between the computer's operating system (OS) and attached devices, such as the hard disk, video adapter, keyboard, mouse and printer.

In modern computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard. Users can periodically check for an updated version.

It is the first thing that loaded when the computer is started even before loading of the operating system. It runs from the PROM, EPROM, or flash memory when the computer is powered on, it initializes several motherboard components and peripheral devices.

How does the BIOS (Basic Input Output System) work?

The first task of the BIOS is to give instructions to the computer for the power-on self-test. This self-test ensures that the computer has all of the necessary parts ( memory, keyboard, and other parts)

It instructs the computer to give an error code(series of beeps heard shortly after startup) if errors are detected during self-test.

After the above activity, BIOS gives basic information to the computer on how to interact with critical components (drivers and memory that are required to load the operating system).

The computer proceeds to load the operating system from the attached drivers once the basic instructions and self-test have been passed.

History of the Basic Input Output System?

The BIOS was created by Gary Kildall and first appeared in the CP/M operating system in 1975, describing the machine-specific part of CP/M loaded during boot time that interfaces directly with the hardware.


The Basic Input Output System regulates the computer machine by operating the related programs. I hope you have learned and enjoyed it a lot.