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What is it?

The binary number system is a base-2 number system. This means it only has two numbers: 0 and 1. All information in a computer (words, pictures, movies, sound) is stored and transmitted as sequences of bits, or binary digits.

A bit is a single piece of data which can be thought of as either zero or one. Each binary number is made up of bits, for example, the number 1010 is made of 4 bits. When you have 8 bits altogether, this is known as a byte. A byte may look like the number 01000100 and in this case represents the letter 'D'.

Australian Curriculum definition


A use of two states or permissible values to represent data, such as ON and OFF positions of a light switch or transistors in a computer silicon chip that can be in either the electrical state of ON or OFF.

Binary data are typically represented as a series of single digits referred to as binary digits (or bits) due to each taking on the value of either 0 or 1. The image below shows how a dashed line might be represented in binary.

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Source: Australian Curriculum: Technologies glossary

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Understanding representation: Part 1

This 7-minute video explores the nature of representation as an arbitrary communication device.

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Understanding representation: Part 2

This 11-minute video explores number representations, including the development of the binary system.

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CS Field Guide: Data representation

This chapter is about some of the different methods that computers use to code different kinds of information in patterns of bits, and how this affects the cost and quality of what we do on the computer.

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Computer Science Unplugged: Part 1 - Binary

This video explains binary numbers.

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James May's 'What are binary numbers?' (video)

James May asks: 'What are binary numbers, and why does my computer need them?'

How to teach it

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Using binary to create on/off pictures

Students develop an understanding of how computers store and send digital images and they are able to represent images in a digital format.

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Everything is numbers!

In this sequence students learn how the binary number system works and how text can be represented using binary numbers. Students learn one of the representations of the standard English alphabet used by computers. They also look at how the same concepts apply to non-text data and analyse the effectiveness of some binary representation techniques to various types of data.

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Introduction to binary

This short sequence focuses on what a binary number is, what a decimal number is (revision), why binary numbers are important in digital systems, and how to read and understand a binary number.

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CS Unplugged: Error detection

Use these activities with your students to explore how a computer figures out if an error has occurred in stored and transmitted data.

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CS Unplugged: Binary numbers

Use these activities with your students to explore how computers use just two symbols, zero and one, to represent information.

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CS Unplugged: Modems unplugged

This activity involves listening to songs and finding hidden messages based on the same principle as a modem. Also suitable for upper primary students.

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CS Unplugged: Image representation

Use these activities with your students to explore how computers store and transmit data to create a black-and-white image. Also suitable for lower secondary students.


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This unit explores the technical challenges and questions that arise from the need to represent digital information in computers and transfer it between people and computational devices.

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Binary Puzzle

The binary puzzle is a new and challenging logic puzzle that students can solve by reasoning. Only zeros and ones occur in the puzzle, but this turns out to be more complicated than it first seems.

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Binary Numbers Magic Trick

This activity uses binary numbers as a way of identifying the magic number.

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ACARA: Binary work samples

Students were introduced to whole numbers using a CS Unplugged video and unplugged group activities. Students completed a worksheet to assess their understanding of binary numbers.

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Good News Lutheran School: Bits of Binary

Teachers at Good News Lutheran School are exploring ways to teach the content and skills of the new Digital Technologies curriculum. The Year 5 teachers collaborated with the Digital Learning Facilitator to present a sequence of lessons introducing the concept of binary numbers through online and unplugged activities.

Level F - 2

Recognise and explore patterns in data and represent data as pictures, symbols and diagrams (ACTDIK002)

Levels 3 - 4

Recognise different types of data and explore how the same data can be represented in different ways (ACTDIK008)

Levels 5 - 6

Examine how whole numbers are used to represent all data in digital systems (ACTDIK015)

Levels 7 - 8

Investigate how digital systems represent text, image and audio data in binary (ACTDIK024)

Levels 9 - 10

Analyse simple compression of data are separated from presentation (ACTDIK035)