OCR GCSE Computer Science – Data Compression | Editable Lesson, Worksheets & Assessment

Lesson objectives:

Define compression and explain why it is needed

Distinguish between lossy and lossless compression

Compare advantages and disadvantages of each method and apply to real-world scenarios

Lesson overview

This engaging lesson introduces students to the concept of data compression in computer systems.
Learners explore how and why files are compressed, the difference between lossy and lossless methods, and how these impact file size, quality, and transmission time.
Practical examples and tasks cover image, sound, and text files, including RLE (Run Length Encoding) and perceptual compression.

What’s included

Editable PowerPoint presentation (step-by-step explanations + visuals)

Student worksheet / activity sheet

Practical scenarios comparing lossy vs. lossless file types

Mix-and-match task for RLE and perceptual compression

Multiple-choice quiz for assessment

Teacher answers for all tasks

Suitable for

OCR GCSE Computer Science (J277)

Unit: Data Representation – Compression

Can also support AQA and Edexcel specifications

Ideal for KS4 Computer Science or as a revision / cover lesson

Learning outcomes

By the end of this lesson, students will be able to:

Explain why compression is needed to reduce storage and transmission time.

Identify and describe lossy and lossless compression techniques.

Evaluate the advantages and disadvantages of each method.

Apply the correct compression type to different file formats and uses.

File types covered

JPG, PNG, GIF, MP3, WAV, ZIP, TXT, BMP – with discussion of which formats use lossy or lossless compression.