How do computers work?

Have you ever wondered how a computer actually works? Have you ever looked inside your computer and wondered what all those parts are? We hope this worksheet will help to answer those questions for you.

What is a computer?

A computer is an electronic device that takes input from the outside world, processes it according to a set of instructions, stores some data and produces output. This is true if you are doing your homework: typing your answers (input), formatting and arranging it on a page (processing), storing it on your computer (storage) and showing it on the screen or printing it out (output). It’s also true if you are using your computer to play a game. You give input to the computer with your keyboard, mouse or controller, the computer responds to your input by moving your character around and checking if you have collided with something, for example. It stores your current position and score and the output is the graphics on the screen and sound.

Input and Output devices

An input device is one that allows you to send data to the computer. An output device is one that the computer sends data to. Can you categorise these devices into input or output devices?

Keyboard
Printer
Screen
Mouse
Microphone
Speakers
Scanner
Projector
Barcode reader

Computers and Electricity

Computers use electric circuits and switches to represent all data and instructions. These switches allow electricity to be on or off in a circuit. We combine lots of circuits and switches to represent data and instructions.

Switches in this state could represent the number 174, the character ® or this colour:

How is this possible and why would we do this?

Computers use electric wires and circuits to carry all information and the electricity in those wires is either on or off. With one wire, you can represent: yes or no; true or false; 1 or 0. We can create codes for colours, text characters and sound and represent them with numbers.

We can then convert these numbers into something called binary. Binary is a counting system that uses two different characters: 0 and 1.

Binary and decimal

Decimal

Think about the numbers you use every day. You are, of course, happy that with a number like 9999 those 9s have different values because they are in different places in the number. The one on the left is worth 9000 because it is in the 1000s column.

This number system is called decimal or base ten. We have ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. The place values are multiplied by ten as you move from right to left.

Binary

Computers use binary to represent all data. Binary is also called base 2. This follows the same system but multiplies by 2 instead of 10. Can you guess how many digits there are in binary? What about the place values, can you fill them in?

If you have got this right, you will have represented the decimal number 15 in binary. Can you see why?

Answers

Input and output devices

Keyboard - input device
Printer - output device
Screen - output device (unless it's a touch screen, then it's both input and output)
Mouse - input device
Microphone - input device
Speakers - output device
Scanner - input device
Projector - output device
Barcode reader - input device