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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 8 marks

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1Multiple choice1 markCompression Swap Remove

Identify one reason for using data compression.

[1 mark]
  • ATo increase the number of packets sent
  • BTo reduce the time taken to transmit a file
  • CTo improve the quality of the file
  • DTo make the file harder to open
Mark scheme
  • B To reduce the time taken to transmit a file (1)
  • The only correct answer is B. The correct answer is to reduce the time taken to transmit a file.
  • A is not correct because compression reduces file size, which can reduce the number of packets sent
  • C is not correct because lossy compression can reduce the quality of a file
  • D is not correct because encryption, not compression, can make a file harder to open
Example answers and how they were marked
Full marks1/1

B To reduce the time taken to transmit a file

Why: Correct option (1).

No marks0/1

A To increase the number of packets sent

Why: Near miss: compression reduces the number of packets sent, so no mark.

No marks0/1

C To improve the quality of the file

Why: Misconception that compression improves quality; no mark.

2Multiple choice1 markUnits & Conversion Swap Remove

A computer stores data in binary.

Identify the number of bits in one kibibyte.

[1 mark]
  • A1024
  • B8000
  • C8192
  • D8 388 608
Mark scheme
  • C 8192 (1)
  • The only correct answer is C. The correct answer is 8192.
  • A is not correct because 1024 is the number of bytes in a kibibyte
  • B is not correct because 8000 is the number of bits in 1000 bytes
  • D is not correct because 8 388 608 is the number of bits in a mebibyte
Example answers and how they were marked
Full marks1/1

C 8192

Why: Correct: one kibibyte is 1024 bytes and 1024 × 8 = 8192 bits (1).

No marks0/1

A 1024

Why: Near miss: 1024 is the number of bytes in a kibibyte, not the number of bits (0).

No marks0/1

B 8000

Why: Typical misconception: uses 1000 bytes for a kibibyte, giving 1000 × 8 = 8000 bits (0).

3Discuss6 marksCompression Swap Remove

A company runs a website advertising holiday cottages. Each page shows photographs of a cottage and has a short audio guide that visitors can play. The company uses lossy compression for the photographs and the audio.

Discuss the use of lossy compression on the company's website.

Your answer should include:

  • how lossy compression makes the files smaller
  • the effect this has on the photographs and audio
  • the benefits to the company and its visitors
[6 marks]
Mark scheme

Indicative content

How lossy compression makes the files smaller

  • Some of the data in the file is permanently removed, so the file that is stored is smaller.
  • The data that is removed is the data that a person is least likely to notice, such as sounds outside the range of human hearing or small differences in colour in a photograph.
  • Removing data means a much higher compression ratio is possible than with lossless compression.

The effect on the photographs and audio

  • The original file cannot be reproduced exactly when it is decompressed.
  • Photographs may show artefacts, such as blocks or noise where there are contrasting colours, so they are lower quality.
  • Some of the sound is lost, so parts of the audio guide may be less clear to listen to.
  • If the company later wants to use the photographs at a larger size, it cannot recover the lost detail.

The benefits to the company and its visitors

  • The smaller images load faster, so each page of the website appears more quickly for a visitor.
  • The audio can be streamed, so a visitor can play the guide without waiting for the whole file to download.
  • Less bandwidth is used by the web server, so it can cope with more visitors at the same time.
  • Less storage space is needed on the server for the photographs and audio files.

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 the effect on the files and the benefits.

Do not accept the idea that lossy compression keeps all of the original data.

Example answers and how they were marked
Full marks6/6

Lossy compression permanently removes some of the data, for example the parts of the sound that the human ear cannot hear, or small differences in colour in a photograph, so the file that is stored is much smaller than it would be with lossless compression. This means the original cannot be recreated exactly: parts of a photograph with contrasting colours may show blocks or noise, and parts of the audio guide may be less clear. However, the smaller images mean each page loads faster for a visitor, and the audio can be streamed so a visitor can play the guide without waiting for the whole file. Less bandwidth is used too, so the server can cope with more visitors at once.

Why: Explains how data is removed and its effect on the photographs and audio, then links the benefits to visitors and to the server, so Level 3.

Some marks3/6

Lossy compression makes the files smaller by removing some of the data. This means the photographs might not look as good as the original. The website pages will load faster for visitors because the files are smaller.

Why: Correct basic points about the method, the effect and a benefit (AO1/AO2), but the points are not developed and the audio is not considered, so Level 2.

Some marks1/6

Lossy compression does not lose any data, so the photographs can be decompressed back to the original picture. The web pages will load faster because the photographs are smaller.

Why: One basic point about faster loading; the description of lossy compression is the wrong way round because data is permanently 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

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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

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