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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 11 marks

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1Multiple choice1 markUnits & Conversion Swap Remove

Units of data storage can be binary or decimal.

Identify the unit of storage that is equivalent to 1024 gibibytes.

[1 mark]
  • AGibibyte
  • BMebibyte
  • CTebibyte
  • DTerabyte
Mark scheme
  • C Tebibyte (1)
  • The only correct answer is C. The correct answer is tebibyte.
  • A is not correct because a gibibyte is 1024 mebibytes
  • B is not correct because a mebibyte is 1024 kibibytes
  • D is not correct because a terabyte is 1000 gigabytes
Example answers and how they were marked
Full marks1/1

C Tebibyte

Why: Correct: 1024 gibibytes make one tebibyte (1).

No marks0/1

A Gibibyte

Why: Near miss: a gibibyte is 1024 mebibytes, not 1024 gibibytes (0).

No marks0/1

D Terabyte

Why: Typical misconception: uses the decimal terabyte (1000 gigabytes) instead of the binary tebibyte (0).

2Short 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.

3Describe2 marksCompression Swap Remove

Data can be compressed using lossy or lossless compression.

Describe one difference between lossy compression and lossless compression.

[2 marks]
Mark scheme

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

  • Lossy compression permanently removes/discards some of the data (1) whereas lossless compression keeps all of the original data so the file can be restored/rebuilt exactly (1)
  • Lossy compression cannot reproduce/recreate the original file exactly (1) whereas lossless compression can decompress the file back to its original form (1)
  • Lossy compression can make a file smaller than lossless compression (1) because more of the original data is removed/discarded (1)
  • Lossy compression is used for images/sound/video (1) whereas lossless compression is used where all the original data must be kept, such as program files (1)

Allow one mark for a correct statement about one type of compression only, e.g. 'lossy compression permanently removes some data', with no comparison or development.

Do not accept 'lossy compression loses quality' on its own unless it states that data/information is removed or lost permanently.

Do not accept 'lossy is better' or 'lossless is safer' with no described difference.

Do not award a smaller file size on its own; it must be linked to data being removed or to no data being lost.

Example answers and how they were marked
Full marks2/2

Lossy compression permanently removes some of the data, whereas lossless compression keeps all of the original data so the file can be restored exactly.

Why: Linked difference: lossy permanently removes data (1) and lossless keeps all data so the file is restored exactly (1).

Some marks1/2

Lossy compression permanently removes some of the data.

Why: A correct statement about one type only (1), with no comparison to lossless or development, so the second mark is not earned.

No marks0/2

Lossless compression removes the data that is not needed so the file is smaller, but lossy compression keeps every bit of the data.

Why: The two types are the wrong way round; no creditworthy point, so no marks.

4Discuss6 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

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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 16 questions Intellectual Property 12 questions

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