Data Capacity and Compression
Calculating storage requirements and evaluating lossless and lossy compression for different data and purposes.
How to study for GCSE Computer Science
Move repeatedly between problem, algorithm, trace, code, test evidence and system explanation; use the exact language and assessment format required by your current board.
Core concepts
Concept 1
Capacity calculations require consistent bit or byte units and clear treatment of decimal or binary prefixes when the question specifies them.
Exam cue: Write the formula, convert units once and label the final unit.
Concept 2
Lossless compression allows exact reconstruction, while lossy compression discards information to achieve different size-quality trade-offs.
Exam cue: Decide whether exact reconstruction is required before selecting compression.
Concept 3
Compression method choice depends on the data, required fidelity, processing cost, transmission constraints and intended use.
Exam cue: Evaluate storage and transmission benefits alongside quality and processing effects.
Risk pitfalls and guardrails
Mixing bits and bytes in one calculation.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Calling all compressed files lower quality.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Assuming the highest compression ratio is always most suitable.
Guardrail: Do not substitute one board's syntax, protocol list, language version or extension topic for the multi-board core; check the current specification and exam year.
Memory anchors
Data capacity
The quantity of data a storage or transmission system can hold or carry.
Compression
Encoding data to reduce the storage or transmission required.
Lossless compression
Compression from which the original data can be reconstructed exactly.
Lossy compression
Compression that permanently discards selected information.
Compression ratio
A comparison between uncompressed and compressed size.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A memory specification gives capacity in bytes. How many binary bits make up each byte?
A file contains 24,000 bits. How many bytes is this?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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