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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 693 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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4 questions · 10 marks

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1Short recall1 markCharacter Sets Swap Remove

ASCII uses 7 bits to store each character. A system has only 6 bits available to store each character.

State the number of different characters the system can represent.

[1 mark]
Mark scheme

Award one mark for:

  • 64 (1)
  • 2^6 (1)
  • 2 × 2 × 2 × 2 × 2 × 2 (1)

Allow 64 characters / sixty-four.

Allow 2 to the power of 6 for 2^6.

Do not accept 128, which is the number of characters that can be represented using 7 bits.

Do not accept 63, the largest value that can be represented using 6 bits, rather than the number of different characters.

Do not accept 12 (2 × 6), ie the number of bits multiplied by 2.

Example answers and how they were marked
Full marks1/1

64

Why: Correct: 2^6 = 64 different characters (1).

No marks0/1

128

Why: Scores 0: 128 is the number of characters that 7 bits can represent, not the 6 bits the system has; the Do not accept line applies.

No marks0/1

63

Why: Scores 0: 63 is the largest value 6 bits can hold, not the number of different characters; the Do not accept line applies.

2Short recall1 markImages Swap Remove

A bitmap image uses one bit per pixel.

State the limitation this places on the number of colours in the image.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • Only two different colours can be represented/stored (1)
  • Each pixel can only be one of two values (1)
  • The image can only be shown in black and white (1)

Allow answers that give the number of colours, e.g. two colours, 2 colours

Allow any pair of two colours, e.g. black and white, black and grey

Do not accept low resolution/poor quality/lower quality

Do not accept only one colour/can only show black

Do not accept 2 bits/2^1 without a statement about the number of colours that can be represented

Example answers and how they were marked
Full marks1/1

Only two colours can be represented, such as black and white.

Why: States that only two different colours can be represented (1)

No marks0/1

The image will have a low resolution.

Why: Confuses colour depth with resolution; low resolution is not accepted

No marks0/1

The image can only show black.

Why: One colour is all a single value can give; the limitation is that only two colours can be represented, so this is not accepted

3Describe2 marksSound Swap Remove

Each sample of a sound is stored as a binary number.

Describe how bit depth affects the stored value of a sound sample.

[2 marks]
Mark scheme

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

  • The bit depth is the number of bits used to store each sample/measurement (1) so a higher bit depth gives more possible/discrete values for the amplitude (1)
  • A higher bit depth records the amplitude more accurately (1) because the stored value can be closer to the actual height of the wave (1)
  • A low bit depth gives fewer possible amplitude values (1) so the amplitude is rounded to the nearest value, making the recording less accurate (1)

Do not accept sample rate/sample interval (number of samples per second) in place of bit depth.

Do not accept 'more bits gives better quality' or 'more accurate' on its own, without a development linked to the number of values or the amplitude stored.

Do not accept file size on its own, and a file size point cannot earn the second mark, as it does not describe the stored value.

Example answers and how they were marked
Full marks2/2

The bit depth is the number of bits used to store each sample, so a higher bit depth gives more possible values for the amplitude that can be stored.

Why: First point, the number of bits per sample (1), then the linked development, more possible values for the amplitude (1).

Some marks1/2

The bit depth is the number of bits used to store one sample.

Why: Gives the first point, the number of bits per sample (1), but does not develop how this affects the value that is stored.

No marks0/2

A higher bit depth makes the sound better quality and more accurate.

Why: Near-miss: 'better quality' and 'more accurate' on their own, with no development linked to the number of values or the amplitude, so no mark is awarded.

4Discuss6 marksImages Swap Remove

A wildlife photographer takes a photograph for a magazine. The photograph can be printed across a full page or used as a small thumbnail on the magazine's website.

Discuss how the resolution of the photograph affects its use in the magazine and on the website.

Your answer should include:

  • what resolution means
  • the effect of resolution on the detail shown
  • the effect of resolution on the file size.
[6 marks]
Mark scheme

Indicative content

What resolution means

  • Resolution is the number of pixels in the image, or the number of pixels per inch.
  • A photograph that is 6000 × 4000 pixels has a higher resolution than one that is 600 × 400 pixels.
  • Resolution is not the same as colour depth or the number of colours.

Effect on detail

  • A higher-resolution photograph has more pixels in the same area, so it can show more detail.
  • A low-resolution photograph printed across a full page will look blocky or pixelated because each pixel is enlarged.
  • A small website thumbnail uses fewer pixels on screen, so a lower-resolution version may still look sharp.
  • A high-resolution original can be cropped and still contain enough pixels for a full-page print.

Effect on file size

  • More pixels means more binary values must be stored, so the file is larger.
  • A large file takes more storage and is slower to upload or download, which matters for visitors to the website.
  • The photographer could make a lower-resolution copy for the website and keep the high-resolution original for print.
  • File size also depends on the colour depth and the file format or compression used.

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 detail and file size.

Do not accept resolution as the number of colours.

Example answers and how they were marked
Full marks6/6

Resolution is the number of pixels in the photograph, for example 6000 × 4000 pixels. A high-resolution photograph has more pixels, so it can show fine detail such as the animal's fur. This is important for the full-page magazine print because a low-resolution image would look blocky when enlarged. The small website thumbnail uses fewer pixels on screen, so a lower-resolution copy would still look sharp and would be suitable. A high-resolution file contains more pixel values, so it takes up more storage space. It would also be slower to download for people viewing the website. The photographer could keep the high-resolution original for print and make a lower-resolution copy for the website.

Why: Defines resolution accurately, links detail to the print use, links file size to storage and download for the website, and gives a sensible recommendation. Sustained application, so Level 3.

Some marks4/6

Resolution means how many pixels are in the image. A higher resolution means the photograph has more pixels, so it can show more detail. This is good for the full-page print because it will not look pixelated. A lower resolution might be enough for the small website thumbnail because it is shown smaller.

Why: Covers what resolution means and its effect on detail, with some application to print and the website. It does not discuss the effect on file size, so it is limited to Level 2.

Some marks1/6

Resolution is the number of pixels in the image. The photograph will have a higher resolution if it has more colours, so it will look sharper in the magazine. The file size is bigger when the resolution is higher, so the website will load faster.

Why: Only the definition of resolution is creditworthy. The answer wrongly links resolution to the number of colours and says a larger file will make the website load faster.

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