Basic Input Output System

What is Basic Input Output System (BIOS)?

Basic Input Output System or BIOS refers to the specific software program used by the microprocessor of a computer to boot up or start the system by passing the control to it when it is powered on.

Technically, BIOS is included in the computer systems as a firmware. It exists in the same place on an Erasable Programmable Read Only Memory or EPROM chip placed on the motherboard.

Understanding Basic Input Output System (BIOS)

What is Basic Input Output System (BIOS)

Also known as the ROM BIOS, System BIOS, PC BIOS or BIOS ROM, the Basic Input Output System is the software program in the EPROM of a computer system that helps in the startup process.

It can also be stored in a flash memory but certainly not in a larger hard drive because it will be unable to boot it from there.

Storing the BIOS in the flash drive helps in rewriting it and making easy updates or adding new features and even fixing bugs by the end user without removing the chip from the motherboard.

However, this may infect the computer system with BIOS rootkits.

Though it is responsible for the basic or initial functions, this particular firmware plays a significant role in the overall functioning of the computer system because it will not boot at all if the program itself is wrong in the first place.

The most common errors that may be related to this firmware are:

In such situations, changes may be required in the BIOS settings or it should be upgraded. However, it should be done very carefully because any error may not boot the system at all.

Also, while upgrading, you must make sure that it is compatible with the operating system installed or else it will corrupt the software program and the system will not boot.

Typically, there is no need for a user to mess with the BIOS of their computer system because if the upgrade does not work, it will brick the motherboard rendering the system useless.

The BIOS library contains a few specific functions to operate and/or control the peripherals of the system. These can be set off via external software.

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The users can even perform several functions using the user interface of this software which include and are not limited to:

There are lots of benefits offered by this firmware but in spite of the good, there are some limitations of the Basic I/O system such as it cannot boot from larger storage drives and when it boots, it does so in the Legacy Mode which is actually a 16-bit real mode and therefore is much slower than UEFI.

Also, offering an option to the end users to upgrade the BIOS may destroy its memory due to carelessness.

Features of BIOS

The features of the firmware display a lot of important information to the users as well as to the operating system of the computer.

Typically, BIOS would include information of the manufacturers of different components of the computer system such as:

In addition to that, the manufacturer will also set the attribute values related to the BIOS in particular such as:

The information may also contain the generic codes required to control the display of the computer, the keyboard and others.

And, to the operating system the BIOS tells how it should function with the devices that it has detected.


The main function of the BIOS is to start a computer system when the users switch it on. It also checks and changes the boot order if necessary and even displays any errors that may occur during the boot up process.

The basic need of this program pre-installed on the motherboard is to help in loading the operating system after checking that all necessary components connected to and available in the system are correct and functioning properly.

It also tells the computer how to perform the basic functions such as booting or keyboard control, and identify hardware and configure CPU, memory, hard drive, optical drive, floppy drive, and other related components before loading the operating system.

The program works quickly and performs these specific functions during the boot up process:

Finally, it loads the operating system, the whole or part of it, into the Random Access Memory or RAM from the hard disk or the diskette drive or any other type of boot device.

Therefore, ideally, the functions typically involve a combination of a few specific steps such as identifying, configuring, testing and connecting the hardware of the computer to the operating system when the system is turned on.

All these functions together are called and complete the boot process.

In order to explain the functions of this firmware in a more precise way, it can be said that it performs four specific roles. This will make it even easier to break down the entire process and BIOS functions in a much better way.

The roles involve the following:

In addition to the above, the function of the BIOS also involves managing the flow of data between the operating system of the computer system and the devices attached to it such as the hard disk, keyboard, mouse, video adapter, and printer.

How Many Types of BIOS are There?

Ideally, there are two types of Basic I/O System such as UEFI or Unified Extensible Firmware Interface and Legacy.

UEFI – This BIOS type can accommodate larger drives of the size of 2.2 TB or more with the help of the MBR or the Master Boot Record approach instead of the more modern GPT or GUID Partition Table technology.

Legacy BIOS – This firmware is found in the older motherboards which works just like the UEFI in governing the communication between the CPU and the other components of the computer.

However, it has a few limitations such as it cannot identify any drive that is larger than 2.1 TB. Also, the setup programs in it contain text-only menus.

Both these boot modes come with their characteristic benefits which you should consider if you are given an option to choose one between the two.

The advantages of installing the UEFI boot mode include:

Why Do You Need a BIOS?

As said earlier, you will need the BIOS to boot up the computer system once you switch it on. Without the BIOS the system will not work.

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The microprocessor in the computer needs someone to act as a middleman between the hardware and the operating system to run on and to carry and control the flow of data and information to the I/O devices. This is actually done by the BIOS.

Apart from that, this firmware also plays an important role in ensuring the security of the computer system. Ideally, most of the versions of this particular software come with an option to protect the boot process with a password.

This means that the booting process will not be initiated if the correct password is not entered in the first place. Since this performs all the initial functions virtually, it helps in protecting the entire computer system and its operation.

Does BIOS Use RAM?

Yes, just like all other codes and programs such as operating systems and user programs, the BIOS also needs to use the RAM of a computer system to be loaded into it so that it can run.

All the parts in the motherboard need to go to the BIOS to check the necessary parts and if something is not right or not present the system will stop working.

Moreover, manufacturers design their system in such a way that the Basic Input Output System is copied to the RAM from the ROM every time the computer is booted since the RAM is faster than the ROM.

When the computer is powered on, the processor loads the BIOS code in a particular address of the system memory. It then jumps to the head of that memory address and performs the necessary functions.

This means that the CPU, after switching the system on, will search for the RAM and it is only after that the BIOS firmware will initiate the boot up process looking for the operating system that is stored in the hard drive and then load it into the RAM.

So, RAM is essential for a computer to function.

Questions & Answers:

Where is the Basic Input Output System Stored?

The BIOS is located in the motherboard stored in the EEPROM chip. This chip is typically non-volatile in nature. This means that you even rewrite or update the BIOS.

Why is BIOS Called Firmware?

Typically, firmware signifies the generic name given to all those software programs that reside on the non-volatile memory. And, since BIOS is stored in the EPROM, it is therefore called firmware that ‘talks’ to the devices and tells the operating system how exactly it is supposed to function with them.


The BIOS is a very important program for a computer which helps the system to boot and start functioning.

Apart from that, it also ensures security of the system and also helps in controlling data flow and setting up the CMOS.

Simply said, without this particular firmware, a computer system is as good as defunct.