1.3

Data storage and compression

Cambridge IGCSE Computer Science (0478)  · Unit 1: Data representation  · 9 flashcards

Data storage and compression is topic 1.3 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 1 — Data representation , alongside Number systems and Text, sound and images.  In one line: Data storage refers to the methods and technologies used to record and retain digital information for later retrieval. It involves using various storage mediums like hard drives, SSDs, or cloud services to preserve data.

This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).

The deck below contains 9 flashcards — 4 definitions, 3 key concepts and 2 application cards — covering the precise wording mark schemes reward.  Use the 4 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

The term 'data storage' in the context of computer science

Data storage refers to the methods and technologies used to record and retain digital information for later retrieval. It involves using various storage mediums like hard drives, SSDs, or cloud services to preserve data.

What the Cambridge 0478 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Understand Understand how data storage is measured including bit, nibble, byte, kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB), pebibyte (PiB), exbibyte (EiB)
  2. Calculate Calculate the file size of an image file and a sound file, using information given
  3. Understand Understand the purpose of and need for data compression
  4. Understand Understand how files are compressed using lossy and lossless compression methods including run length encoding (RLE)
Definition Flip

Define the term 'data storage' in the context of computer science.

Answer Flip

Data storage refers to the methods and technologies used to record and retain digital information for later retrieval. It involves using various storage mediums like hard drives, SSDs, or cloud services to preserve data.

Key Concept Flip

Arrange the following units of storage in ascending order: Terabyte (TB), Kilobyte (KB), Gigabyte (GB), Megabyte (MB).

Answer Flip

The correct order is: Kilobyte (KB), Megabyte (MB), Gigabyte (GB), Terabyte (TB). Remember that 1KB < 1MB < 1GB < 1TB.

Definition Flip

Explain the purpose of data compression.

Answer Flip

Data compression reduces the size of a file or data stream. This is done to save storage space and bandwidth during transmission, making it more efficient to store or send the data.

Definition Flip

What is 'lossy' compression and provide an example of a file format that uses it.

Answer Flip

Lossy compression reduces file size by permanently removing some data. An example is JPEG for images, where some image quality is sacrificed for a smaller file size.

Definition Flip

Explain 'lossless' compression and give an example of a file format that uses it.

Answer Flip

Lossless compression reduces file size without losing any data. The original data can be perfectly reconstructed. An example is ZIP or PNG for images.

Key Concept Flip

Describe how Run Length Encoding (RLE) works.

Answer Flip

RLE replaces consecutive repeating occurrences of a symbol with a count of the repetition followed by the symbol itself.

Example: 'AAABBBCC' becomes '3A3B2C'.
Key Concept Flip

Give an example scenario where RLE compression would be effective.

Answer Flip

RLE is effective for compressing images with large areas of the same color, such as simple graphics or black and white images with long runs of black or white pixels.

Key Concept Flip

Outline one advantage and one disadvantage of using lossy compression.

Answer Flip

Advantage: Significantly smaller file sizes compared to lossless. Disadvantage: Some data is permanently lost, reducing the quality of the reconstructed file.

Key Concept Flip

Explain why lossless compression is preferred for text documents and program code.

Answer Flip

Lossless compression is preferred because any data loss in text or code can corrupt the file, rendering it unusable or causing errors. Perfect reconstruction is necessary.

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1.2 Text, sound and images 2.1 Types and methods of data transmission

Key Questions: Data storage and compression

Define the term 'data storage' in the context of computer science.

Data storage refers to the methods and technologies used to record and retain digital information for later retrieval. It involves using various storage mediums like hard drives, SSDs, or cloud services to preserve data.

Explain the purpose of data compression.

Data compression reduces the size of a file or data stream. This is done to save storage space and bandwidth during transmission, making it more efficient to store or send the data.

What is 'lossy' compression and provide an example of a file format that uses it.

Lossy compression reduces file size by permanently removing some data. An example is JPEG for images, where some image quality is sacrificed for a smaller file size.

Explain 'lossless' compression and give an example of a file format that uses it.

Lossless compression reduces file size without losing any data. The original data can be perfectly reconstructed. An example is ZIP or PNG for images.

More topics in Unit 1 — Data representation

Data storage and compression sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

1.1 Number systems

10 flashcards
1.2 Text, sound and images

10 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

storage kilobyte megabyte gigabyte terabyte compression lossy lossless run length encoding RLE

Key terms covered in this Data storage and compression deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

The term 'data storage' in the context of computer science
Explain the purpose of data compression
'lossy' compression and provide an example of a file format that uses it
Explain 'lossless' compression and give an example of a file format that uses it

How to study this Data storage and compression deck

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