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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 687 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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3 questions · 5 marks

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1Short recall2 marksCompression Swap Remove

Images and sound can be stored using lossy compression.

Define the term lossy compression.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • Reduces the size of a file (1)
  • Permanently removes/loses some data (1)
  • The original file cannot be recreated/restored exactly (1)

Allow 'some data is deleted/discarded and cannot be recovered' for the second mark.

Do not award the first mark where the response also states that no data is lost.

Do not accept 'removes repeated data' (this describes lossless compression).

Example answers and how they were marked
Full marks2/2

Lossy compression reduces the size of a file by permanently removing some data, so the original cannot be restored exactly.

Why: Reduces the size of a file (1); permanently removes some data (1); maximum two marks awarded.

Some marks1/2

It makes a file smaller.

Why: Reduces the size of a file (1); no reference to data being permanently lost.

No marks0/2

It makes a file smaller without losing any of the data.

Why: States that no data is lost, which describes lossless compression; the first mark is not awarded.

2Short 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.

3Describe2 marksCompression Swap Remove

A school compresses its text documents before backing them up.

Describe how lossless compression reduces the size of a text file.

[2 marks]
Mark scheme

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

  • Repeated words/patterns are found (1) and stored once in a dictionary with a code (1)
  • Each repeated word/pattern is replaced by a shorter code (1) so fewer bits are needed to store the text (1)
  • No data is removed (1) so the original text can be recreated exactly (1)
  • The compressed file is smaller (1) but all the original characters can still be restored (1)

Do not accept answers that say data is permanently removed or quality is reduced.

Example answers and how they were marked
Full marks2/2

It finds repeated words in the document and stores them once in a dictionary with a code.

Why: Linked point: repeated words found (1) and development: stored once in a dictionary (1).

Some marks1/2

It makes the file smaller without losing any of the data.

Why: States that no data is lost (1); no linked method or exact restoration is given (1).

No marks0/2

It removes repeated characters permanently so the file takes up less space.

Why: Describes permanent removal, which is lossy, not lossless; no credit.

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