Data Storage and Compression
Data Representation · 4 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 4% of your exam marks.
File size calculations and lossless vs lossy compression are regular 3 to 4 mark questions.
shrinks a file so it takes up less room. Three standard exam-friendly reasons to compress:
| Reason | What it means |
|---|---|
| Less storage space | More files fit on the same disk; lower storage cost |
| Faster transmission | Smaller files upload, download or stream more quickly |
| Less bandwidth used | Less data crosses the network, which matters on metered or mobile connections |
A typical Cambridge question gives 3 marks for stating three distinct reasons. Distinct is the key word: "saves disk space" and "uses less storage" are the same reason in two different wordings.
There is always a cost. A compressed file has to be decompressed before it can be opened, which takes processor time. And some compression methods discard information that can never be recovered (covered next).
There are two completely different families of compression methods: lossless and lossy.