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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 5 marks

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1Short recall1 markCompression Swap Remove

A company backs up its files to an external hard drive.

Give one reason why the company compresses the files before backing them up.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • More files/data can be stored (in the same storage space) (1)
  • The files take up less storage space (1)
  • The backup is quicker/faster to complete (1)
  • Less data needs to be transferred to the backup device (1)

Do not accept 'makes the files more secure' or 'encrypts the files'.

Example answers and how they were marked
Full marks1/1

The compressed files take up less storage space, so more files can be backed up.

Why: The files take up less storage space (1).

No marks0/1

It reduces the amount of disk fragmentation.

Why: Near-miss: compression does not reduce disk fragmentation.

No marks0/1

It encrypts the files so they are safer if the drive is stolen.

Why: Misconception: compression does not encrypt files, and security is not accepted.

2Explain2 marksCompression Swap Remove

A solicitor sends large documents to clients by email.

Explain one reason why the solicitor compresses the documents before sending them.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • The file size is reduced (1) so the documents take less time to transmit/send (1)
  • The compressed files are smaller (1) so they are more likely to be within the email attachment size limit (1)
  • Less data is sent (1) so less bandwidth/data allowance is used (1)
  • Fewer packets are needed (1) so the documents are received more quickly (1)

For both marks, the expansion must follow/associate with the statement.

Do not accept 'it saves storage space' on its own without linking to sending the documents.

Do not accept 'it makes the file smaller' as both the point and the reason.

Example answers and how they were marked
Full marks2/2

The documents take up less space so they are quicker to send by email.

Why: File size reduced (1) and linked reason that transmission is quicker (1).

Some marks1/2

It makes the documents smaller.

Why: File size reduced (1) but no linked reason about sending or transmission.

No marks0/2

It reduces the amount of storage space the documents use on the client's computer.

Why: Storage space alone is not a reason for compressing before sending, so no linked explanation point is credited.

3Explain2 marksCompression Swap Remove

A software company distributes its programs as compressed files.

Explain why lossless compression is used for the program files.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • No data/instructions are removed (1) so the program still works/runs correctly after decompression (1)
  • The original file can be recreated exactly (1) so all the code/instructions are present when the program is run (1)
  • Lossy compression would permanently remove some data (1) so the program would not execute correctly/could crash (1)
  • Every instruction is needed for the program to run (1) so the code must not be changed/lost (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'no data/instructions are removed/lost' on its own as the point mark (1); the second mark needs the consequence for the program, e.g. it still works/runs correctly, or all the instructions are present.

Award credit for a contrast with lossy compression only when the loss of data is linked to the program failing/not running correctly.

Do not accept 'lossless is better quality'/keeps the quality without saying that data/instructions are not lost.

Do not accept 'it makes the file smaller'/'downloads faster'/'transmits faster' as a reason for using lossless, as both types of compression reduce file size.

Example answers and how they were marked
Full marks2/2

No instructions are removed so the program still works after it has been decompressed.

Why: No data/instructions removed (1) and linked reason that the program still works correctly (1).

Some marks1/2

Lossless compression does not lose any data.

Why: Point mark for 'no data/instructions are lost' on its own (1); no consequence for the program is given, so the second mark is not awarded.

No marks0/2

Lossless compression makes the file smaller so it downloads faster.

Why: File size and download speed apply to both types of compression, so this does not explain why lossless is used for the program files.

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