Oxford Cambridge and RSA
GCSE (9-1) Computer Science
Computer Systems
J277/01
Topic: Unit 1.2 Compression
Time allowed: 20 minutes
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INSTRUCTIONS
Use black ink.
Answer all the questions.
INFORMATION
The total mark for this paper is 16.
The marks for each question are shown in brackets [ ].
Turn over
1
Files are often compressed before they are transmitted over the Internet.
(a) State two benefits of compressing a file.
[2]
1.
2.
(b) Tick one box in each row to identify whether the statement applies to Lossy or Lossless compression.
[3]
Statement
Lossy
Lossless
The original file can be perfectly reconstructed
Data is permanently removed from the file
Usually achieves a much smaller file size than the other method
2
A student is emailing a Python program code file (game.py) to their teacher.
They need to compress the file to make it smaller.
(a) Identify which type of compression (Lossy or Lossless) the student must use.
[1]
(b) Explain why the other type of compression would be unsuitable for this specific file.
[2]
Turn over
3
A web designer is uploading a high-resolution photograph to a website.
They choose to use Lossy compression rather than Lossless.
(a) Explain one reason why Lossy compression is the better choice for images on a website.
[2]
(b) Explain one negative effect of using Lossy compression on the image.
[2]
4
Explain the fundamental difference between Lossy and Lossless compression.
In your answer, refer to what happens to the data when the file is uncompressed (restored).