Compression & Storage Units

Watch first — Craig 'n' Dave

Craig 'n' Dave · Edexcel 1CP2Compression

Key facts

Lossy vs lossless compression — fill in the table

Term	Definition
Lossy compression
Lossless compression

Jun 2022 Q3(b): "Lossy" is correct for an image that cannot be fully recreated. Jun 2023 Q5(a): lossy compression means removed data cannot be restored / original file cannot be fully recreated.

Run-length encoding (lossless) — fill in the table

Point	Detail
Method
Example
Effective for
Not effective for
Type

Storage units — must know — fill in the table

Unit	Size
Byte
Kilobyte (KB)
Megabyte (MB)
Gigabyte (GB)
Terabyte (TB)
Tebibyte

Exam questions — 4 questions · 12 marks · from real 1CP2 past papers

1 markLossy vs lossless1CP2 Jun 2022 Q3(b) style

An image file is compressed and the original file cannot be fully recreated from the compressed version. What type of compression was used?

A Lossless compression

B Lossy compression

C Run-length encoding

D Encryption

2 marksAdvantages of compression1CP2 Jun 2022 Q2(e) style

Give two advantages of compressing files before sending them over a network. (2 marks)

Hint: Give two distinct advantages. Each needs to explain WHY compression helps for that specific thing.

+20 XP

4 marksDiscuss lossy compression1CP2 Jun 2023 Q5(a) style

Explain why lossy compression means a file cannot be fully recreated, and describe a situation where lossy compression is appropriate and one where it is not. (4 marks)

Hint: Explain WHY data is lost → give one appropriate use case → give one inappropriate use case with reasoning.

+40 XP

Quick recall flashcards

Lossy vs lossless compression — fill in the table

Run-length encoding (lossless) — fill in the table

Storage units — must know — fill in the table

Module complete! 🎉