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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 markCharacter Sets Swap Remove

A text file stores each character using 7-bit ASCII.

Identify the denary ASCII code for the space character.

[1 mark]
  • A32
  • B33
  • C48
  • D65
Mark scheme
  • A 32 (1)
  • The only correct answer is A. The correct answer is 32.
  • B is not correct because 33 is the ASCII code for the exclamation mark (!)
  • C is not correct because 48 is the ASCII code for the character 0
  • D is not correct because 65 is the ASCII code for the uppercase letter A
Example answers and how they were marked
Full marks1/1

A 32

Why: Correct option: the space character has the ASCII code 32 (1).

No marks0/1

C 48

Why: Near miss scoring 0: 48 is the ASCII code for the character 0, not the space character.

No marks0/1

D 65

Why: Misconception scoring 0: 65 is the ASCII code for the uppercase letter A, so a well-known code is given but not the code for a space.

2Describe2 marksCharacter Sets Swap Remove

A computer uses 7-bit ASCII to represent characters.

The character M has the ASCII code 77. Describe how the character M is represented in the computer.

[2 marks]
Mark scheme

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

  • The denary code 77 is converted to binary (1) to give the 7-bit pattern 1001101 (1)
  • The character M is represented by a unique ASCII code/number (1) that is stored as a 7-bit binary pattern (1)
  • 7 bits are used to store the code for M (1) so 128 different characters can be represented (1)
  • The binary pattern 1001101 is stored in memory (1) using one 7-bit code for each character (1)

Do not accept answers that only state the ASCII code 77, as this is given in the question.

Do not accept 01001101, as this is an 8-bit pattern.

Do not accept ASCII described as a programming language or a method of encryption.

Example answers and how they were marked
Full marks2/2

77 is converted to binary, giving 1001101. This is stored using 7 bits for the character M.

Why: Linked description: converts the code to binary (1) to give the 7-bit pattern 1001101 (1).

Some marks1/2

77 is changed into binary so it can be stored.

Why: Gives the conversion of 77 to binary (1) but does not give the 7-bit pattern 1001101 (0).

No marks0/2

ASCII is a programming language that stores letters as numbers.

Why: Describes ASCII as a programming language, which the mark scheme says is not creditworthy; no linked description of how M is represented.

3Explain2 marksImages Swap Remove

An image uses a colour depth of 2 bits per pixel. The original image contains 12 different colours.

Explain why the image cannot be represented accurately at this colour depth.

[2 marks]
Mark scheme

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

  • Only 4 colours can be represented (1) because 2 bits give 2^2 = 4 possible values (1)
  • Some of the 12 colours cannot be stored (1) so they are lost/replaced with a colour that can be represented (1)
  • The image will not match the original exactly (1) because there are fewer colour codes than the number of colours needed (1)
  • Many colours will share the same binary value (1) so the image will lose colour detail (1)

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

Allow 'four colours' or '2^2'.

Do not accept 'only two colours' (confusing the number of bits with the number of values) or 'resolution is too low'.

Example answers and how they were marked
Full marks2/2

Only four colours can be represented because two bits give four possible binary values.

Why: Linked point (1) and reason (1): 2 bits give 2^2 = 4 colour codes.

Some marks1/2

Only four colours can be represented.

Why: One mark for identifying that four colours can be represented; the linked reason about two bits giving four values is missing.

No marks0/2

Only two colours can be represented because each pixel has two bits.

Why: A common misconception: two bits give four possible values, not two, so no creditworthy point is given.

4Discuss6 marksImages Swap Remove

A handheld games console displays sprites. The console stores each pixel of a sprite using 4 bits. Designers want sprites that contain many shades of green and blue.

Discuss the limitations of using 4 bits to store each pixel of a sprite on the console.

Your answer should include:

  • the number of colours that can be represented
  • the effect on the appearance of the sprite
  • how the limitation could be managed.
[6 marks]
Mark scheme

Indicative content

Number of colours

  • 4 bits give 2^4 = 16 different binary values, so at most 16 colours can be stored for each pixel.
  • The console cannot store every shade that the designers want; colours outside the 16 must be approximated or left out.
  • Adding more bits per pixel would allow more colours, but this may not be possible on the console's hardware.

Effect on appearance

  • The sprite may show banding where a smooth change from green to blue should be.
  • A sprite that needs many shades, such as a detailed landscape, will look unrealistic or have blocks of colour.
  • Simple sprites with flat colours, such as a retro character, can still look acceptable.
  • The limitation is in the number of colours, not the number of pixels; resolution is a separate issue.

Managing the limitation

  • Designers can choose a palette of 16 colours that includes the most important greens and blues for the game.
  • They can design sprites with flat colours rather than smooth gradients.
  • They can use more bits per pixel for important sprites if the console allows it.
  • They can accept that some shades will be approximated and check that the sprite still looks clear on the console's screen.

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 the number of colours and the effect on appearance.

Do not accept 4 bits give 4 colours or 8 colours.

Example answers and how they were marked
Full marks6/6

4 bits per pixel gives 2^4 = 16 different binary values, so each pixel can be only one of 16 colours. The designers want many shades of green and blue, but most of these cannot be stored exactly and must be approximated or left out. This can cause banding where a smooth change from green to blue should be, so a detailed sprite may look unrealistic. A simple sprite with flat colours could still look acceptable. The designers could choose a palette of 16 colours that includes the most important greens and blues, and design sprites with flat colours instead of gradients. Using more bits per pixel would allow more colours, but the console's hardware may not support this.

Why: Explains 2^4 = 16 colours and the limitation on shades, links this to banding and realism, and gives suitable ways to manage it in the console context. Sustained reasoning, so Level 3.

Some marks4/6

4 bits can store 16 colours. This means the sprite cannot have many colours. It might look bad if it needs lots of shades of green and blue. The designers could use fewer colours in the sprite.

Why: Correctly gives 16 colours and makes a simple link to the sprite's appearance and a way to manage it. There is little development of the effect or the management, so Level 2.

Some marks1/6

4 bits can store 16 colours. This means the sprite will have a low resolution, so it will look blocky. The designers should use a higher resolution to get more shades of green and blue.

Why: One correct point: 4 bits give 16 colours. The answer then confuses colour depth with resolution; increasing resolution would not provide more shades.

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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