GCSERevise
AQASpec 3.3Foundation & Higher~35 min

Data Representation

Computer Science · Topic revision workspace

Topic progress0%

Read the notes, score 80% and know 75% of the cards.

Topic overview

What you need to know

Computers represent every data type in binary. Revise number conversion, character encoding, bitmap images, digital sound, compression and storage units.

Exam tip

Write place values above binary digits and show conversions. For files, multiply dimensions, colour depth or sample data before converting units.

Revision notes

Core ideas

Secure these ideas first. Say each definition in your own words, then connect it to the topic overview.

  • Bit: A binary digit with the value 0 or 1.
  • Character set: A defined mapping between characters and binary codes, such as ASCII or Unicode.
  • Colour depth: The number of bits used for each pixel, controlling available colours.

Revision notes

Apply it in the exam

The exam will rarely ask for an isolated definition. Practise selecting the right idea and using it as part of a complete explanation or method.

  • Sample rate: The number of sound measurements captured per second.
  • Lossless compression: Reducing file size without discarding data, allowing exact reconstruction.
  • Lossy compression: Reducing file size by permanently removing data judged less important.

Core knowledge

Key facts for Data Representation

1

Bit

A binary digit with the value 0 or 1.

2

Character set

A defined mapping between characters and binary codes, such as ASCII or Unicode.

3

Colour depth

The number of bits used for each pixel, controlling available colours.

4

Sample rate

The number of sound measurements captured per second.

5

Lossless compression

Reducing file size without discarding data, allowing exact reconstruction.

6

Lossy compression

Reducing file size by permanently removing data judged less important.

Active recall

Close the notes and answer these

  1. 1.Without looking, explain bit and give one example or consequence.
  2. 2.Without looking, explain character set and give one example or consequence.
  3. 3.Without looking, explain colour depth and give one example or consequence.
  4. 4.Without looking, explain sample rate and give one example or consequence.

Content reviewed 23 July 2026 against the current linked specification.

Finished learning?

Mark the notes complete, then test what you can recall.

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