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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 6 marks

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1Multiple choice1 markCompression Swap Remove

A student downloads a compressed music file and then decompresses it.

Identify what is meant by decompression.

[1 mark]
  • AData is encrypted so that it cannot be read
  • BData is permanently removed to reduce the file size
  • CData is restored to its original format
  • DData is stored using fewer bits
Mark scheme
  • C Data is restored to its original format (1)
  • The only correct answer is C. The correct answer is data is restored to its original format.
  • A is not correct because encryption changes data so that it cannot be read without a key; it does not restore the data
  • B is not correct because permanently removing data to reduce the file size is lossy compression, not decompression
  • D is not correct because storing data using fewer bits is compression, not decompression
Example answers and how they were marked
Full marks1/1

C Data is restored to its original format

Why: Correct option (1).

No marks0/1

D Data is stored using fewer bits

Why: Near miss: this describes compression, not decompression.

No marks0/1

B Data is permanently removed to reduce the file size

Why: Misconception: this describes lossy compression, not decompression.

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.

4Explain2 marksCompression Swap Remove

Files can be compressed using lossy or lossless compression.

Explain one difference between lossy compression and lossless compression.

[2 marks]
Mark scheme

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

  • Lossy compression permanently removes some data (1) whereas lossless compression does not remove any data (1)
  • With lossy compression the original file cannot be recreated exactly (1) but with lossless compression it can (1)
  • Lossy compression can produce a smaller file/a higher compression ratio (1) whereas lossless compression keeps all of the data so compresses less (1)

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

Allow 'removes data' for 'permanently removes data'.

A correct statement about only one type of compression, with no contrast, earns one mark.

Do not accept a reversed statement such as 'lossless compression loses data and lossy compression does not'.

Do not accept 'lossy makes the file smaller' on its own, because lossless compression also reduces the file size; the answer must say that data is removed.

Do not accept 'lossy is worse quality' on its own without saying data is removed.

Example answers and how they were marked
Full marks2/2

Lossy compression removes some data permanently, but lossless compression keeps all of the data.

Why: Lossy removes data permanently (1) and contrasts with lossless keeping all data (1).

Some marks1/2

Lossy compression removes some of the data.

Why: A correct statement about one type of compression with no contrast earns one mark (1); no contrasting statement about lossless compression is given.

No marks0/2

Lossless compression removes data so the file is smaller, but lossy compression keeps all the data.

Why: Reversed statement: lossless keeps all the data and lossy removes it, so no mark is awarded.

Questions by topic

2.1 Binary

Build a paper on this topic 58
Adding Binary Numbers 6 questions Binary and Hexadecimal Basics 10 questions Binary Shifts 6 questions Binary to Denary Conversion 6 questions Binary to Hexadecimal Conversion 6 questions Denary to Binary Conversion 6 questions Denary to Hexadecimal Conversion 6 questions Denary to Negative Binary Conversion 6 questions Hexadecimal to Binary Conversion 6 questions

2.2 Data representation

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Character Sets 18 questions Images 19 questions Sound 19 questions

2.3 Data storage and compression

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Compression 18 questions Units & Conversion 6 questions

3.1 Hardware

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Embedded Systems 17 questions Fetch Decode Execute Cycle 15 questions Primary Memory 15 questions Secondary Memory 15 questions Stored Program Computers 15 questions

3.2 Software

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File Management 18 questions Memory Management 16 questions Peripheral Management 11 questions Process Management 12 questions Purpose & Function of Operating Systems 17 questions Software Basics 13 questions User Management 18 questions Utility Software 19 questions

3.3 Programming languages

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Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

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Addressing 16 questions LANs & WANs 16 questions Network Speed 5 questions Packet Switching 16 questions Protocols & Layers 17 questions The Internet 16 questions Topologies 17 questions Wired Connections 17 questions Wireless Connections 18 questions

4.2 Network security

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Network Security Risks 18 questions Preventing Network Security Risks 18 questions

5.1 Environmental

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E-waste 17 questions Manufacturing Technology 19 questions

5.2 Ethical and legal

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Data Protection Act 17 questions Impact of AI 18 questions Intellectual Property 18 questions Software Licences 18 questions

5.3 Cybersecurity

Build a paper on this topic 36
Malware 18 questions Social Engineering 18 questions

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