O-LevelComputer ScienceData Representation2210/11 · May/June 2019 · Q55 Marks
The following text is stored as a text file: She sells sea shells on the seashore. The shells that she sells are sea shells I am sure. Explain how lossless compression would compress this file.
- (a)Explain how lossless compression would compress this file.[5]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [1] A (compression) algorithm is used
- [1] No data is removed in the process // original file can be restored
- [1] Repeated words (are identified) // Patterns in the data (are identified)
- [1] and are indexed/put into a table // by example
- [1] and are replaced with their index // by example
- [1] and their positions are stored (in the table) // by example
- [1] and the number of times the word/pattern appears is stored (in the table) // by example
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