The main components of a computer system

You must watch the video to the end to complete this lesson. Once you have watched the video and completed the tasks, please click on “Mark As Complete” at the top right of your screen.

TopicI should be able to…
1.2Describe the central processing unit (CPU) including its role
Describe internal memory, i.e. ROM and RAM and the differences between them
Define input and output devices and describe the difference between them
define secondary/backing storage

Much of what you will see in this lesson will be extended & revision from our first lesson, and we’ll be continuing to look at the internal parts of the computer system in this lesson.

The Purpose of The CPU

In the last lesson, we watched the video on the purpose of the CPU.

The purpose of the CPU is to control both hardware and software to the user, provide an interface (hiding the complex systems), and to manage memory. To do this, an Architecture needs to be used to allow the CPU to understand how to process the instructions within the device.

Purpose of the CPU - fetch decode execute

The tasks that the CPU performs can be broken down into Fetch, Decode, and Execute. This is referred to as the Fetch Execute Cycle and allows your computer to function.

Imagine your CPU like your brain in the classroom:

  • You arrive and are given a list of tasks
  • You select (fetch) the first task
  • You work out (decode) what you are being asked to do
  • You get any data that the task needs
  • You perform (execute) the task
  • Then you move on to the next task

The CPU in your computer can vary in size and power, but they are all there for the same purpose… to be the brain of the computer system!

Internal Memory : RAM & ROM

In order for a brain to work, it needs to be able to retain some of the information & data that is passed in. This is where the primary memory of the computer comes in. The primary memory is always internal – this means that it’s inside the computer can often difficult to remove. This allows it to be physically close to the CPU.

In the last lesson we looked at how RAM is used to hold the currently running instructions & data. However, RAM is not the only type of internal memory – watch the video below on the purpose of ROM:

Activity 1

Download & print the notes below. Fill in each of the sections with notes from the videos to help you remember your key terms.

Activity 2

Use the interactive board below to create a diagram of the internal parts of a computer.

Input vs Output Devices

One of the definitions that you’ll be asked about early on in the course will be the difference between an input & an output device. Remember that both of these are hardware devices, so they are physical which means you can touch them (although while the computer is on, it may not mean you should touch them!).

An Input device is hardware that allows the user to enter data into the computer system.

An output device is hardware that gives the user data from the computer system.

Activity 3

Use the Blooket linked below to test your understanding of Input & Output devices (you may need a free account to access this to play in solo mode)

Play Input/Output Blooket

Secondary Storage

Whilst Primary Memory (ROM & RAM) is used to run the system, a computer also needs places to store programs and data for longer. The term used to describe these types of media is secondary storage. These come in three main types: magnetic, optical, and solid state.

Watch the video below, then download and complete the notes on Types of Storage: