What is BIOS and its Functions

What is BIOS

What is BIOS

BIOS stands for Basic Input Output System. BIOS is a small program which is pre-installed on Widow based computer systems. It is used to start up the computers.  It is the first program which is installed in Windows computers even before the operating system.

When we switch on a computer, the CPU accesses the BIOS to locate all Input-Output devices and check if all hardware connections are properly functional. It is BIOS which loads the operating system in the computer memory, thus completing the process of booting.

 A computer user need not do any changes in BIOS as it is installed at the time of configuration of the computer. Now the question arises if BIOS loads the operating system and manages all hardware including hard drives, then where does the BIOS reside?

The correct answer is that BIOS Input-output System is a part of the motherboard.  The BIOS is stored in the permanent memory that is non- volatile Read-Only Memory (ROM) or Erasable Programmable Read-Only Memory (EPROM) chip or Flash memory on the motherboard of a computer.

Also read – What is Read-Only Memory (ROM)?

Non- volatile or flash memory is capable of keeping the data intact even if the power is switch off which means the contents are not deleted.  EPROM and Flash memory is used to make it possible to upgrade the BIOS program as we can alter the contents of EPROM and Flash memory.  

Another advantage of flash memory is that we can modify the flash memory on the motherboard only while if EPROM is used we need to remove the EPROM chip from the motherboard and then alter its contents using EPROM programmer.  

After the booting process is complete, the BIOS acts as a mediator between the Input-Output devices (I/O devices) and the CPU. For Operating system or the process running on your computer, it is not necessary to have all the information about the hardware attached. 

Also read – Motherboard and its classifications

All the details of the hardware of the computer are known to and managed by the BIOS. Whenever IO device information changes, then this information needs to be communicated to the BIOS. To enter into BIOS setup, follow the following steps:

  1. Switch ON the Power Button of the computer.
  2. As soon as the computer starts switching ON, press and hold the F2 or Delete/ Del key to enter the BIOS setup.
  3. BIOS setup page will appear.  Now make the necessary changes.
  4. Press F10 key to save the changes and exit the BIOS set up

Functions of BIOS

The BIOS is responsible for loading basic computer hardware and booting of the operating system.  The BIOS contains various instructions for loading the hardware. It also conducts a test which aids in verifying if the computer meets all the basic requirements for booting. This test is called the Power On Self Test or simply POST.

The computer starts beeping if the POST test fails to indicate that there is some issue within the computer.

The main functions of BIOS are as follows:


 The first and foremost function of BIOS is to make sure that the computer hardware is functioning properly and there is no issue with the hardware. This is done by the Power On Self Test (POST). If the POST test fails computer generates different types of beeps to indicate the type of error. If the POST test is passed then booting starts.


After successful completion of POST, the BIOS locates and identifies the operating system. The BIOS then passes the control to the Operating system if it finds one. This is called booting.

BIOS drivers

 The BIOS drivers are a collection of programs that are stored in the non- volatile erasable memory chips. The BIOS Drivers gives basic information about computer hardware.

BIOS Setup

It is a configuration program that permits us to configure hardware settings. BIOS setup is also known as CMOS setup. BIOS or CMOS setup includes:

  1. Loading of the BIOS Setup Default
  2. Changing the booting order
  3. Creation or deletion of the BIOS Password
  4. Setting or Changing the Date and Time
  5. Changing Floppy Disc, Hard Drive or CD/DVD Settings
  6. Check Memory Installed status
  7. Enabling or Disabling the Computer Logo
  8. Enabling or Disable the Quick POST
  9. Enable or Disable the CPU Internal Cache
  10. Enable or Disable the Caching of BIOS
  11. Change CPU Settings
  12. Change Memory Settings
  13. Change System Voltages
  14. Enable or Disable RAID
  15. Enable or Disable Onboard USB, Audio ports and serial/ parallel Ports
  16. Enable or Disable Onboard Floppy Controller
  17. Enable or Disable ACPI
  18. Change the Boot Up NumLock Status
  19. Change the Advanced Configuration and Power Interface (ACPI) Type
  20. Change the Power Button Function
  21. Change Power-on Settings
  22. Change Which Display is Initialized First on Multi-Display Setups
  23. Reset Extended System Configuration Data (ESCD)
  24. Enable or Disable BIOS Control of System Resources
  25. Change and view Fan Speed Settings
  26. View CPU and System Temperatures
  27. View System Voltages

The Bottom Line

The functions of BIOS is a set of instructions which are integral and vital part of Firmware of motherboard and is responsible for Checking the hardware connected to a Computer and booting thus handing over the control of the computer to the operating system. Now think if you can imagine a computer without BIOS?

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