We answer: What is BIOS and how to use it?

Milan Stanojevic
by Milan Stanojevic
Windows & Software Expert
Milan has been enthusiastic about PCs ever since his childhood days, and this led him to take interest in all PC-related technologies. Before joining WindowsReport, he worked as a front-end web developer. Read more
Affiliate Disclosure
  • BIOS is an acronym for Basic Input/Output System and it's a critical component of your PC.
  • BIOS is installed on a small chip on your motherboard and was invented in 1975.
  • This software is the first to run after you press the ON button on your PC.
  • In the present days, BIOS is being replaced by UEFI, a more efficient tool.
What is BIOS
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Even if you’re not an advanced PC user, you might have heard the term BIOS before. BIOS is an important part of every computer, and today we’re going to explain you what is BIOS and how does it work.

What is BIOS and what it can do

1. What is BIOS and a short history

BIOS is an acronym for Basic Input/Output System, and it’s a firmware that’s built into your motherboard.

Every motherboard comes with BIOS, and in fact, BIOS is the first software that starts once you press the power button on your PC.

Although BIOS is a standard part of every computer nowadays, that wasn’t always the case. In the 70’s computers didn’t have BIOS, and instead they started the operating system as soon as you pressed the power button.

This method had many flaws, and of the biggest flaws was related to operating system failure. These types of problems are one of the main reasons why BIOS was invented in 1975 by Gary Arlen Kildall.


2. What does BIOS do?

As previously mentioned, BIOS is the first software that starts when you power on your PC. BIOS is in charge of checking your hardware, and it will do that every time during the POST (power-on self-test) sequence.

Before your operating system can start, BIOS will perform a check and identify all the basic hardware components such as your CPU, RAM, keyboard, graphic card, hard drive, and DVD drive.

If everything is in order, BIOS will now search for boot loader software. This software is stored on your hard drive or removable media, therefore BIOS will scan all available boot devices.

If a bootable device is found, the BIOS will boot your PC from it. As you can see, BIOS is crucial when starting your PC, but BIOS also allows you to change the configuration settings of your hardware components.

For example, you can use BIOS to change the boot device order, which is especially important if you want to boot your PC from a bootable USB flash drive in order to install Windows 10 again.

BIOS also allows you to change other hardware settings. For example, certain versions of BIOS allow you to change the frequency of your CPU or RAM, thus allowing you to overclock it.

Bear in mind that overclocking will cause your hardware to emit extra heat, and that can sometimes cause permanent damage to your PC.

BIOS allows you to change all sorts of hardware settings, and in order to learn all settings that you can change, we strongly suggest that you check your motherboard manual.

As you can see, BIOS allows you to change wide range of settings, and in order to save these settings, BIOS relies on CMOS volatile memory.

This memory is powered by the battery on your motherboard, and in case the motherboard battery is empty or broken, you won’t be able to save BIOS changes and BIOS will always revert to default settings.

In the past, before BIOS was invented, there was no way to fix your PC if your operating system was corrupted.

Nowadays you can simply boot your PC from a DVD or USB flash drive and reinstall your operating system or back up your important files.


3. What happens if BIOS gets corrupted?

This is why BIOS is such an important part of every PC, but what if your BIOS gets corrupted?

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BIOS is stored in a small chip on your motherboard, and if that chip is faulty, your computer won’t be able to start without BIOS.

It’s not common for BIOS chip to become faulty, but if that happens, you won’t be able to use that motherboard anymore.

Some PC experts can replace BIOS chips if they aren’t working anymore, however, this is an advanced procedure that should be performed only by professionals.

To fix the problem with faulty BIOS, motherboard manufacturers started creating motherboards that have two chips that store BIOS.

In case the main BIOS chip fails, you can restart your computer and use the backup BIOS instead.


4. Updating your BIOS

It’s important to know that users can also update their BIOS. Motherboard manufacturers are releasing updated versions of BIOS, and these updates bring improved hardware compatibility and bug fixes.

We have to warn you that updating BIOS comes with certain risks, and if you don’t perform BIOS update properly, or if you abort the update process you can permanently damage your motherboard.

Newer motherboards use boot block that runs first, and the boot block has to be updated separately.

The boot block is in charge of checking your BIOS, and if the corruption is detected, user will get a warning message saying that he needs to flash BIOS again by using a removable media.

Since you can update your BIOS, does that mean that malicious users can enter their code and infect your BIOS?

There are at least four BIOS viruses available, and most of these viruses were created just for demonstration purposes.

BIOS virus attacks are rare, but not impossible, and if your BIOS is infected by virus it’s highly advised that you contact a security expert.


5. BIOS, replaced by UEFI

Since computer technology is constantly evolving, so is BIOS, and it seems that BIOS is surely being replaced by UEFI (Unified Extensible Firmware Interface).

UEFI is basically modern and more powerful BIOS, and most new motherboards come with UEFI instead of BIOS.

UEFI has the same features as BIOS, but it offers a better user interface along with some features that BIOS lacks.

Even though the first version of UEFI was released in 2005, UEFI gained popularity after the release of Windows 8.

Microsoft added native support for UEFI in Windows 8 and this is one of the main reasons behind the popularity of UEFI.


As you can see, BIOS is a crucial component of every PC because it allows you to change all sorts of settings related to your hardware.

If you wish to learn more about the settings that you can change in BIOS, we strongly suggest that you check your motherboard manual.

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