Full Form of BIOS: What is BIOS in Computer?

You may have heard the term 'BIOS' many times in the field of computers. There are possibilities that you may have even used the BIOS without knowing. But something you may not have noticed is that the term BIOS is just an abbreviation. So, what is the full form of BIOS?

In this article, we have briefly covered the most important things about BIOS, such as the BIOS full form, what is BIOS, its features, functions, and more.

What You Will Learn

What is the full form of BIOS?

BIOS stands for "Basic Input Output System". Other terms commonly used for BIOS are system BIOS, ROM (Read Only Memory) BIOS, and PC or Personal Computer BIOS, etc.

Full Form of BIOS

The full form of BIOS can be explained as:

B Basic
I Input
O Output
S System

Let’s talk about what BIOS is:

What is BIOS?

BIOS is the first program that a computer runs as soon as it is turned on. The software is usually stored in a ROM chip (EEPROM chip) assembled on the motherboard. The BIOS comes preinstalled with a computer because is the lifeline for any computer system to help initialize hardware during the booting process.

A computer cannot continue without BIOS as it checks whether all the components are connected and are in working condition. Then, it loads the drivers of the hard disk and other basic components of operating system like MBR, GPT, FAT, etc., into the computer’s RAM to enable OS to continue loading itself.

As technology continuously growing, the modern computer systems store BIOS on flash memory, to ease the process of rewriting the contents into BIOS chip, whenever the BIOS update is pushed by the manufacturers.

BIOS: Software or Hardware?

This is one of the most asked questions whether BIOS is software or hardware. Let’s make it clear.

BIOS is a built-in boot firmware program or software that works with the hardware. This means that this built-in software interacts with the hardware components to make the operating system work. But as we know that we need storage to save any software. So, the software is stored in a BIOS chip on the motherboard.

The following image displays a user interface of BIOS (called BIOS Setup Utility) found on the computer systems:

Full Form of BIOS - BIOS Setup Utility

The assembled BIOS chip looks like the following image:

Full Form of BIOS - BIOS in Computer Motherboard

History of BIOS

Going back to the BIOS history, the term was first introduced by Gary Kildall of Digital Research, Inc.in 1975. BIOS was initially released in CP/M operating systems. CP/M or Control Program for Microcomputers was specifically developed for Intel 8080/85-based microcomputers. Such systems came out with a simple boot loader in their ROM.

Types of BIOS

Generally, BIOS is classified into the following two types:

Legacy BIOS

As the name states, the legacy BIOS are the basic forms of BIOS coupled in the older computer systems. Legacy BIOS supports limited features due to a backend functioning. Unfortunately, these types of BIOS don’t support drives larger than 2.1 TB. Also, legacy BIOS offers a text-only user interface for BIOS setup utility.


The complete form of UEFI is “Unified Extensible Firmware Interface”. These BIOS are usually found on modern computers. There is no option to switch from legacy BIOS to UEFI unless we include new hardware that supports UEFI. The UEFI can boot from drives of 2.2 TB or higher and makes boot process faster.

Functions of BIOS

The primary function of BIOS is to initialize hardware components and ensure that all the functioning parts are working properly. It also provides a medium to manage the flow of data between the computer’s operating system and the hardware components such as hard disk, video card, mouse, keyboard, and other I/O devices.

Following is the list of some other activities performed by BIOS:

BIOS performs the Power on Self-Test (called POST) as soon as the computer system starts. It is used to check hardware related issues.

BIOS initializes the Bootstrap sequence and manages Bootstrap Loader. This means that the BIOS transmits the control to the computer’s operating system to continue loading itself.

Bootstrap Driver configures basic hardware to enable a computer system to operate properly. These are low-level drivers that contain the basic information of computer's hardware components.

BIOS is used to access system settings and specify the default boot device.

BIOS stores data like computer’s date, time, and other system configurations in a battery-powered, non-volatile memory chip, known as CMOS. This is the reason why your computer’s date and time does not change even after when it is turned off.

Features of BIOS

BIOS are developed specifically for a particular type of motherboard or computer system.

Initially, BIOS firmware was designed in such a way that it could only be stored into the ROM memory but today's computers have the ability to have it stored in the Flash memory. This is beneficial when we want to rewrite the BIOS contents because it allows updating the chip's contents without removing it from the motherboard.

Many manufacturers provide updates for BIOS firmware so that bugs can be fixed and new features can be added.

One of the biggest advancements of BIOS is UEFI.

Advantages of BIOS

Better compatibility and management of hardware components.

Improvements in the overall performance of the system.

More control to a user over the computer's basic settings.

Disadvantages of BIOS

The time-consuming process as BIOS often boots in 16-bit real mode.

If anything goes wrong during the BIOS initialization or rewriting its content, the motherboard might get affected.

If the BIOS chip gets corrupted, fixing this will be a complex process.


As the name speaks, BIOS (stands for Basic Input Output System) is one of the most important parts of a computer, and loading the operating system without BIOS is not feasible. It is built-in software and the very first software that is run by the computer when we turn on the computer.

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