What is Lossless Compression?
- Reduces file size WITHOUT losing any data
- Original file can be perfectly reconstructed
- Uses patterns and redundancy to make files smaller
- Typical reduction: 30-70% smaller (varies by file type)
When to Use Lossless:
- Text documents: Word files, PDFs, code - every character matters
- Programs/executables: One wrong bit = program crashes
- Medical images: X-rays, MRI scans - diagnosis requires exact detail
- Legal documents: Contracts, evidence - must be identical to original
- Scientific data: Research data, measurements - accuracy critical
Common Lossless Formats:
- ZIP, RAR, 7z: General file compression/archiving
- PNG: Lossless image format (screenshots, diagrams, graphics with text)
- FLAC: Lossless audio (music archiving, audiophiles)
- GIF: Simple animations and graphics (limited to 256 colors)
- GZIP: Web compression (HTML, CSS, JavaScript files)
This key facts covers Lossless Compression - Perfect Recreation within Compression for GCSE Computer Science. Revise Compression in 3.3 Data Representation for GCSE Computer Science with 16 exam-style questions and 16 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Compression
Which statement correctly describes lossy compression?
Explain how run-length encoding (RLE) works to compress data.