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is numbers!

Years 7-8

In this sequence students learn how the binary number system works, how we can represent text using binary numbers and learn one of the representations of the standard English alphabet used by computers. They 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.

Learning hook

By the end of Year 5–6, students should have already explored the idea that all data in digital systems is represented using numbers. 

  1. To get students thinking about this again, set them a challenge. Tell them:
     'I'm going to write a message on the board in a secret code, and you 're going to have to work out what it says.'
  2. Using a simple letter -> number translation (where A = 1, B = 2, … , Z = 26), write a short sentence up on the board (or reveal a pre-prepared one on your projector) using only numbers.
    For example, 'HELLO WORLD' -> 8, 5, 12, 12, 15, 23, 15, 18, 12, 4

(You might want to consider an alternative pattern for classes with a bit more experience. This could be something like {A=1, B=3, C=5,...,M=25, N=2, O=4,...,Z=26} where a pattern is still present but the numbers don't map directly in the same order as the letters. This will be a good primer for our exploration of the ASCII character set later in the lesson.) 

Students should be quite familiar with this idea, so it shouldn't take them too long to work out what the pattern is.

If they need some assistance, you can give them a clue such as 'each number represents a different letter', which is just a more explicit phrasing of the question but should be enough to get them over the line.

It's a good idea to challenge students to think about values arbitrarily.

  • does A have to be 1?
  • What if we reversed the order?
  • What if the numbers were assigned to letters randomly?
  • Why might we want to use a pattern?

  1. Congratulate them on their successful code-breaking skills, and remind them that they should remember that in the past we've explained that computers can represent all data as numerical values. 
  2. Explain that our brains do a similar thing, but that we're able to represent the data we store in lots of different ways – everything from images, sounds and text, which we can then recall and use to answer questions, make decisions or communicate more generally with other people.

    Computers can do some of the things that we can do, but they don't have the same capacity because they are much simpler. They could store the code we used for the text, but how might they do it for an image or sound? 

    We'll start the lesson by finding out how a computer works generally, and then see what this means for multimedia data.

Learning map and outcomes

Share the learning map and outcomes

  • learning how the binary number system works, and how we can represent text using binary numbers
  • learning one of the representations of the standard English alphabet used by computers
  • looking at how the same concepts apply to non-text data
  • analysing the effectiveness of some binary representation techniques to various types of data.

You could also focus on the skillset and mindsets that learners might need to adopt and use during this project, this ties in with the Creative and Critical Thinking Capabilities. Read the effective teaching section, learning: knowledge and beyond for further guidance on this.

Learning input and construction

Students will complete a series of activities, each one with its own Learning input and construction activity. You can select which order to complete them in, but the recommended sequence is:

  1. CS Unplugged: Count the dots
  2. CS Unplugged: Colour by Numbers
  3. CS Unplugged: Codes in a Song
  4. Sampling Sound

Each of these activities has been designed to be accessible to very young students, and each provides a detailed explanation of how the learning outcomes relate to computer systems.

During and at the end of each activity, make sure you devote time to exploring the questions and problems posed in each. The linked resource effectiveness of data representation provides some support for teachers to discuss with students at the end of each activity.

The CS Field Guide provides more activities and variations that you can use to explore these same concepts. It will be particularly useful for students who are wanting to know more and can grasp the basics quickly. Consider how you can incorporate it into your lesson plans. 

Learners will find that they can complete the activities with practice, and this will build confidence with other computing concepts as they begin to realise that the same ideas can be applied in different ways.

Encourage students to have fun with these activities.

  • Delve into the extensions provided in each, and if students are really getting excited about one of them, keep exploring it.
  • Ultimately, the similarity of the concepts means that once a sound grasp of one is achieved, the others are a relatively small jump to understanding.
  • If they want to try coming up with their own system or variant on the theme, let them do so, even if it turns out it is not very good This will provide useful stimulus for discussion when analysing the effectiveness of each method of representation.

A good summary of much of the content covered in these activities is provided by the How Computers Work: Information video. Have students watch this video at the end of the lesson sequence to reinforce the concepts covered.

Learning demo

Have students select their favourite activity from those they completed in this module and ask them to identify which part of the activity was the most surprising to them. 

  • Was it a specific technique used by the computer to represent the data?
  • Was it the general concept that was most intriguing?

Learning reflection

Finally, ask which part of the activity had the greatest impact on their learning. Was it:

  • the introductory reading 
  • working through examples
  • thinking about the more open-ended questions that the new knowledge presented? 

Is this a common experience for them in other classroom activities in other subjects?