What is BIOS (Basic Input Output System) and what does it work?


BIOS (Basic Input Output System) is the basic software of a computer without which it is not possible to start any computer. So if you do not know about BIOS, then read this article till the end, in which you will know what is BIOS (Basic Input Output System) how it works.

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What is BIOS (Basic Input Output System)

The BIOS (Basic Input Output System), which represents the basic input-output system, is software stored on a small memory chip ROM on the motherboard. This is the BIOS responsible for POST (Power On Self Test) and hence the BIOS is the first software to run POST when the computer is started.

The BIOS is pronounced as by-oss and is sometimes referred to as the system BIOS, ROM BIOS, or PC BIOS.

However, it is also incorrectly referred to as the Basic Integrated Operating System or Built-in Operating System.

The picture below is an example of what a BIOS chip might look like on a computer motherboard. The example diagram below is of an early AMIBIOS, a type of BIOS created by AMI.


The BIOS contains instructions for loading basic computer hardware. It also includes a test referred to as POST (Power-On Self-Test) that helps meet the requirements to properly boot a computer. If the computer does not pass the POST, you receive a combination of beeps to indicate what is wrong with the computer.

What is the BIOS used for?

The BIOS instructs the computer how to perform basic tasks such as booting and keyboard control.

PhoneixBIOS Setup Utility
PhoneixBIOS Setup Utility

BIOS is also used to identify and configure hardware such as hard drive, floppy drive, optical drive, CPU, memory, and related devices in computers.

How to access BIOS.

The BIOS is accessed and configured through the Setup Utility. All available options in the BIOS can be configured or accessed through the BIOS Setup Utility.

The BIOS cannot be downloaded and installed in the same way as you install the BIOS on the computer by downloading other software or an operating system like Windows. The BIOS is installed by the manufacturer in the ROM memory chip itself, the BIOS is installed from the moment the machine is built.

BIOS Setup Utility is accessed in various ways depending on your computer or motherboard and model.

PC BIOS has four main functions.

  • POST – POST is a test that tests computer hardware to ensure that there are no errors before loading the operating system.
  • Bootstrap Loader – Operating system is detected. And if a capable operating system is located, the BIOS will pass control to it.
  • BIOS drivers – low-level drivers that give the computer basic operational control over your computer’s hardware.
  • BIOS setup or CMOS setup – Configuration program that allows you to configure hardware settings including system settings such as computer passwords, time and date.


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