Data Representation · 4 question types
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.
Lossless compression reduces file size without removing any data. The original file can be perfectly reconstructed when the file is decompressed.
Key features:
How it works: lossless methods look for patterns, redundancy and repetition in the data and replace them with a more compact code that can later be reversed. There are many algorithms, but the one named in the IGCSE syllabus is run length encoding (RLE).
Common lossless formats: PNG images, FLAC audio, ZIP archives, GIF images, PDF documents (which use lossless compression internally).