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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 10 marks

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1Explain2 marksCharacter Sets Swap Remove

Characters typed on a keyboard are stored using ASCII.

Explain how the computer encodes the letter A using ASCII.

[2 marks]
Mark scheme

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

  • The computer looks up the character in the ASCII character set/table (1) to find the code that represents it (1)
  • Each character has its own unique ASCII code (1) so the letter A is converted to and stored as a 7-bit binary pattern (1)
  • ASCII uses 7 bits for each character (1) so A is stored as its ASCII code 1000001 (binary) / 65 (denary) (1)

The second mark requires a linked expansion, so a point on its own (e.g. 'A has the code 65') can only earn one mark.

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

Accept an 8-bit pattern with a leading 0 (e.g. 01000001) as the binary code for A.

Do not accept 'the character is stored as text' without saying it is changed into a code/binary.

Do not accept a binary value on its own (e.g. 1000001) without saying that it is the ASCII code/that the character is converted to it.

Example answers and how they were marked
Full marks2/2

The computer finds the unique ASCII code for A, which is 65 in denary, and stores it as the 7-bit binary pattern 1000001.

Why: Linked point that A is given its unique ASCII code (1) and reason/expansion that it is converted to and stored as a 7-bit binary pattern (1).

Some marks1/2

The computer changes the letter A into a number.

Why: Gives the point that the character is given a code/number (1) but no linked expansion saying it is converted to binary or stored, so stays on one mark.

No marks0/2

The letter A is stored as the number 1 because it is the first letter of the alphabet.

Why: Wrong reason and no creditworthy point: it does not say that the character is given its ASCII code and converted to binary.

2Explain2 marksImages Swap Remove

Two versions of the same photograph are displayed at the same size on a screen. Version A is 800 × 600 pixels. Version B is 1600 × 1200 pixels.

Explain why Version B can show more detail.

[2 marks]
Mark scheme

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

  • Version B has more pixels in the same area (1) so each pixel represents a smaller part of the image (1)
  • Version B has a higher pixel density (1) so finer detail can be represented (1)
  • The pixels in Version B are smaller (1) so more detail can be captured in the same space (1)
  • Version B has a higher resolution (1) because there are more pixels per unit of area (1)

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

Do not accept 'more pixels' on its own without saying same area/pixel density/smaller pixels.

Do not accept higher colour depth or more colours.

Example answers and how they were marked
Full marks2/2

Version B has more pixels in the same area so each pixel represents a smaller part of the image.

Why: Linked point (1) and reason (1): more pixels in the same area means smaller pixels and more detail.

Some marks1/2

Version B has more pixels in the same area.

Why: One mark for the point about pixel density; the linked reason about smaller pixels or finer detail is missing.

No marks0/2

Version B has a higher colour depth, so it can display more colours.

Why: Colour depth is not the reason for more detail here; this is the common misconception that colour depth increases resolution.

3Discuss6 marksSound Swap Remove

A school records its end-of-year concert. The recording will be put on the school website as an audio file. The school wants the recording to sound as close to the live performance as possible, but the file must not be too large.

Discuss how the sample rate and the sample interval used to digitise the concert affect the quality of the recording and its file size.

Your answer should include:

  • the meaning of sample rate and how it relates to sample interval
  • how changing them affects the accuracy of the recording
  • the effect on the size of the audio file.
[6 marks]
Mark scheme

Indicative content

Sample rate and sample interval

  • The sample rate is the number of samples taken each second, measured in hertz (Hz).
  • The sample interval is the time between one sample and the next.
  • The sample interval is the reciprocal of the sample rate, so doubling the sample rate halves the sample interval.
  • A higher sample rate therefore gives a shorter sample interval, so the concert is measured more often.
  • A lower sample rate gives a longer sample interval, so fewer points on the sound wave are recorded.
  • The school could sample at 44,100 Hz, taking 44,100 measurements of the concert every second.

Accuracy of the recording

  • A higher sample rate, and so a shorter sample interval, records more points on the sound wave, so its shape is followed more closely and the recording is more like the live performance.
  • A higher sample rate can capture high-frequency sounds in the music, such as a violin, more accurately.
  • With a low sample rate the gap between samples is long, so fast changes such as a drum beat can happen between samples and be missed, making the recording less accurate.
  • If the sample rate is too low, a high-frequency sound changes several times between samples, so the digital file does not represent that sound properly.

Effect on file size

  • Each sample is stored using a number of bits, so more samples each second means more data to store for each second of the concert.
  • The file size is the sample rate multiplied by the bit depth multiplied by the duration, so doubling the sample rate doubles the size of the file for the same concert.
  • A lower sample rate means fewer samples are stored, so the file is smaller and quicker to download from the school website.
  • A higher sample rate gives a more accurate recording but a larger file, so the school must trade off quality against file size.

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)

Additional guidance

  • Level 3 responses must cover both sample rate and sample interval, including how they are related, and link them to the accuracy of the recording and to the file size. For Level 2, the response must link a change in sample rate/sample interval to the accuracy of the recording and link a change to the size of the file, with some application to the concert; definitions alone, or points that are not linked, are Level 1.
  • Accept reasoning that uses sample rate only, or sample interval only, if the relationship between them is stated or implied. Do not accept sample rate described as the number of bits per sample (that is bit depth), and do not accept the claim that a higher sample rate makes the file smaller.
Example answers and how they were marked
Full marks6/6

The sample rate is the number of samples taken each second and is measured in hertz. The sample interval is the time gap between one sample and the next, so it is the reciprocal of the sample rate: a higher rate means a shorter interval. If the school uses a high sample rate, such as 44,100 Hz, the interval between samples is short, so the analogue-to-digital converter measures the concert wave very often and follows its shape closely. This makes the recording more accurate, because quiet details and fast drum beats are less likely to happen between samples and be missed, and high notes from the violins are captured properly. However, every sample is stored using bits, so 44,100 samples each second means much more data for each second of the concert and a much larger file, which could download slowly from the school website. If the school halves the sample rate, the interval doubles, the file is half the size, but fast changes in the music may be missed and the recording will sound less like the live performance, so the school must trade off quality against file size.

Why: Level 3 (6 marks): defines both terms, states the reciprocal link, explains why a short interval gives accurate capture (wave shape, fast changes, high frequencies) and why more samples per second means more data, applies all of this to the concert and the website, and draws a trade-off.

Some marks3/6

The sample rate is how many samples are taken each second. The sample interval is the time between each sample, so a higher sample rate means a shorter sample interval. If the school uses a higher sample rate, more of the concert is measured each second, so the recording is more accurate. A higher sample rate also makes the audio file bigger, which will download more slowly from the school website. The school should not use a sample rate that is too high or the file will be too large.

Why: Level 2 (3 marks): definitions are correct and the reciprocal link is stated, and there is one link to accuracy and one link to file size with some application to the concert, but nothing on why slow sampling misses detail and no mechanism for the file-size increase, so it is adequate rather than comprehensive.

Some marks1/6

The sample rate is the number of bits used for each sample. A higher sample rate gives a more accurate recording, so the school should use the highest sample rate so that the concert sounds just like the live performance.

Why: Level 1 (1 mark): one basic correct point, that a higher sample rate gives a more accurate recording; the definition confuses sample rate with bit depth and is not credited, and no point is made about the file size.

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

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Malware 18 questions Social Engineering 18 questions

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