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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 514 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 · 8 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 markUnits & Conversion Swap Remove

A file has a size of 2 kibibytes.

State the number of bytes in the file.

[1 mark]
Mark scheme

Award one mark for:

  • 2048 (1)
  • 2 × 1024 (1)
  • 2^11 (1)

Allow 2048 bytes.

Do not accept 2000, which is the number of bytes in two decimal kilobytes.

Do not accept 1024, which is the number of bytes in one kibibyte.

Do not accept 16, which is the number of bits in two bytes.

Example answers and how they were marked
Full marks1/1

2048

Why: 2048 is 2 × 1024, the number of bytes in 2 kibibytes (1).

No marks0/1

2000

Why: 2000 uses the decimal kilobyte, not the binary kibibyte; the mark scheme does not accept it.

No marks0/1

16

Why: 16 is the number of bits in two bytes, confusing bits with bytes; the mark scheme does not accept it.

3Discuss6 marksCompression Swap Remove

A software company stores the source code of its programs and large text documents on its file server. The company decides to use lossless compression on these files.

Discuss the use of lossless compression for the company's files.

Your answer should include:

  • why lossless compression is suitable for these files
  • how lossless compression makes a file smaller
  • the benefits to the company
[6 marks]
Mark scheme

Indicative content

Why lossless compression is suitable

  • No data is removed, so the original file can be restored exactly when it is decompressed.
  • Source code must be reproduced exactly, because a single missing or changed character would stop the program working when it is run.
  • A text document must keep every character, so that the meaning of the document is not changed.

How lossless compression makes a file smaller

  • Run length encoding stores a repeated value once, together with a count of how many times it appears, so long runs of the same character are held in less space.
  • Dictionary encoding finds patterns or words that are repeated in the text, stores each one once in a dictionary and replaces every occurrence with a short code.
  • The more repetition there is in a file, the greater the reduction in size that can be achieved.

Benefits to the company

  • The compressed files take up less space on the file server, so more programs and documents can be stored.
  • There is less data to transfer, so backing the files up to another location finishes sooner.
  • The company does not need to keep a separate uncompressed copy as well, because the compressed file can be restored exactly, which saves more storage space.
  • The files must be decompressed before they are used, which takes time each time a file is opened.

Levels

  • Level 0 (0 marks): No rewardable content.
  • Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
  • Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
  • Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover both why lossless compression is suitable and how it makes a file smaller.

Do not accept the idea that lossless compression removes data that is not needed.

Example answers and how they were marked
Full marks6/6

Lossless compression is suitable because no data is removed, so the source code can be restored exactly. If even one character were lost or changed the program would not run correctly, and a text document would no longer mean the same thing. Run length encoding can store a run of the same character once with a count of how many times it appears, and dictionary encoding stores each repeated word once in a dictionary and replaces every occurrence with a short code, so a document with lots of repetition becomes much smaller. The compressed files take up less room on the file server, so more programs and documents can be stored, and there is less data to send when the company backs the files up, so the backup finishes sooner.

Why: Explains suitability with a consequence for source code, describes two lossless methods, and applies the benefits to the company's server and backups, so Level 3.

Some marks3/6

Lossless compression does not lose any data, so the file can be decompressed back to the original. This is good for source code because the code will still work. It also saves space on the file server.

Why: Correct definition applied to the code plus one benefit (AO1/AO2), but the method of compression is not described and the benefits are not developed, so Level 2.

Some marks1/6

Lossless compression removes the parts of the file that are not needed so it becomes smaller. The company should use it because the files will be smaller on the server.

Why: One basic point about the files being smaller; the explanation of lossless compression is wrong because data is not removed, so Level 1.

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

Build a paper on this topic 56
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

Build a paper on this topic 124
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

Build a paper on this topic 138
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

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