1.3 Data Storage and Compression
Model Answers
Course
CIEIGCSE Computer Science
Section
1.Data Representation
Topic
1.3 Data Storage and Compression
Topic
Medium
Time allowed: 30
Score: /19
Percentage: /100
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1
i)
C; [1 mark]
ii)
●
lossy
●
lossless; [2 marks]
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2
i) Four from:
− (Compression) algorithm is used; [1 mark]
− No data will be removed // original file can be restored; [1 mark]
− Example of type of algorithm that would be used e.g. RLE; [1 mark]
− Repeated patterns in the music are identified; [1 mark]
− ... and indexed; [1 mark]
NOTE: If another lossless method is described, marks can be awarded.
ii) Any one from:
− To provide the highest quality of music file (that compression will allow); [1 mark]
− The user is able to listen to the original sound file; [1 mark]
− No loss of quality for the sound file provided; [1 mark]
iii) Any one from:
− Allow for quicker streaming speed; [1 mark]
− Would not require as much bandwidth (to stream); [1 mark]
− Does not need as much RAM; [1 mark]
− Smoother listening experience // less lag; [1 mark]
− Will not use as much of data allowance; [1 mark]
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iv) Two from:
− Streaming speed may be slower; [1 mark]
− ... and may affect listening experience // buffering may occur; [1 mark]
− User may need more bandwidth to stream; [1 mark]
− ... that could be more expensive; [1 mark]
− It would be a larger file size; [1 mark]
− ... so may take longer to upload; [1 mark]
− ... so will take up more storage space ...; [1 mark]
− ... on webserver; [1 mark]
[Total: 8 marks]
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3
i) One from:
− Lossy (compression); [1 mark]
Any three from:
− A (compression) algorithm is used; [1 mark]
− Removes redundant/unnecessary data from the file; [1 mark]
− Removes sounds that cannot be heard by the human ear/background noise; [1 mark]
− Reduces sample rate; [1 mark]
− Reduces sample resolution; [1 mark]
− Data is permanently removed // original file cannot be re-instated; [1 mark]
− Perceptual music shaping is used; [1 mark]
NOTE: If lossless given, marks can be awarded for a correct description of lossless as follow through.
Any three from (lossless):
− A (compression) algorithm is used; [1 mark]
− Repeating patterns are identified; [1 mark]
− … are replaced with a value; [1 mark]
− … and indexed; [1 mark]
− No data is permanently removed // original file can be re-instated; [1 mark]
− Suitable example of a lossless algorithm; [1 mark]
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ii) Any two from:
− Quicker for her to upload; [1 mark]
− Quicker for users to download; [1 mark]
− Won’t slow website down as much when loading; [1 mark]
− Takes up less storage space; [1 mark]
[Total: 6 marks]
4
i) Any one from:
– unit of data/memory
– 8 bits
– used to represent a character
; [1 mark]
ii) 30; [1 mark]
[Total: 2 marks]
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