Software classification

Quick links


Hardware and software


Boolean logic


Software classification


Systems architecture


Useful links

Syllabus content

Content   Additional Information

Explain what is meant by:

  • • system software
  • • application software.

Give examples of both types of software.


Understand the need for, and functions of, operating systems (OS) and utility programs.

Understand that the OS handles management of the:

  • • processor(s)
  • • memory
  • • I/O devices
  • • applications
  • • security


What is BIOS?


Short for Basic Input/Output System, the BIOS (pronounced bye-oss) is stored on a ROM chip located on all motherboards that allows you to access and set up your computer system at the most basic level. In the picture below, is an example of what a BIOS chip may look like on your computer motherboard. In this example, this is a picture of an early AMIBIOS, a type of BIOS manufactured by the AMI. Another good example of a BIOS manufacturer is Phoenix. BIOS is known as EFI (extensible firmware interface) on Macs.


It is however, much more than the name suggests. One might think that the BIOS controls input and output system. But the BIOS does much more and it is not possible for any operating system to continue without a proper BIOS in place. The BIOS includes instructions on how to load basic computer hardware and includes a test referred to as a POST (Power On Self Test) that helps verify the computer meets requirements to boot up properly. If the computer does not pass the POST, you will receive a combination of beeps indicating what is malfunctioning within the computer.

The four main functions of a PC BIOS (explained in more detail below)

  • POST - Test the computer hardware and make sure no errors exist before loading the operating system. Additional information on the POST can be found on our POST and Beep Codes page.
  • Bootstrap Loader - Locate the operating system. 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 or CMOS Setup - Configuration program that allows you to configure hardware settings including system settings such as computer passwords, time, and date.

BIOS has been there in computers since the days of DOS - Disk Operating System - even prior to the structured DOS created by Microsoft. It is one of the most important components of the computer though it does not take the credit by appearing on your screen regularly. This post also looks at the most basic component of computers and explains why is it required in computers for computers to work.

usually it is possible to access BIOS as the PC runs through the POST. Pressing a specific function key, F3, F8 or F12 are favourite but it is the designer's choice.

This is the opening page of a BIOS configuration.

What is BIOS in computer

BIOS is a firmware, in short. It is stored on a chip on a part of the computer motherboard and is basically, a set of instructions that run to help load the operating system. The OS would fail to load, if not for the BIOS!

When you turn on the computer, BIOS instructions are initiated. These instructions make it check the RAM and the Processor (for faults) on the computer.

  1. It enumerates the RAM by checking each compartment to see if all of them are working.
  2. After checking out RAM and Processor, it checks for other devices attached to the computer.
  3. It detects all the peripherals, including the keyboard and mouse and then checks for the boot options. The classic error message that causes much amusement is keyboard error press F1 to continue.
  4. Boot options are checked in the sequence configured on the BIOS: Boot from CD-ROM, Boot From Hard Drive, Boot from LAN etc.
  5. It checks for bootstraps on the devices in the order you or the machine vendor configured the BIOS.
  6. It passes the reigns of the computer to operating system by loading the essential parts of the OS into the random access memory (RAM) reserved for the OS, after bootstrap is located.

This is not a comprehensive list of functions of the BIOS. It also checks up CMOS, and other chips to set up the date and time on the computer, and to load the device drivers into the memory. It checks and uploads input and output interrupts (signals) to the RAM so that the operating system knows what is happening. For example, if a user presses a key, an interrupt request is created and passed on to the BIOS which sends it to the operating system. The operating system then decides what action to take, according to the way it is programmed.

Further reading

Here are a few links to web sites and intersting things that you really should read in your own time. There may be a sentence or two in one of these sites that might spark a difficult concept or resolve a confusing idea or may simply be a better explanation that suits you and eanables you to fully understand the points that the examiner is trying to make.

A history of early programming that explains compilers and assemblers in more detail.


3.1 Fundamentals of algorithms

3.2 Programming

3.3 Fundamentals of data representation

3.4 Computer systems

3.5 Fundamentals of computer networks

3.6 Fundamentals of cyber security

3.7 Ethical, legal and environmental impacts of digital technology on wider society, including issues of privacy

3.8 Aspects of software development

Glossary and other links

Glossary of computing terms.

AQA 8520: The 2016 syllabus

Software classification.

Why does a computer need an operating system?

How do operating systems work?

What is Linux?

What is BIOS?

Further reading