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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 631 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 markSound Swap Remove

A digital sound representation is created by sampling an analogue sound wave.

State one way the accuracy of this representation can be increased.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • Increase the sample rate / take more samples per second (1)
  • Increase the bit depth/sample resolution / use more bits per sample (1)
  • Decrease the sample interval (1)

Do not accept increase the amplitude/volume

Do not accept decrease the sample rate / increase the sample interval

Example answers and how they were marked
Full marks1/1

Increase the sample rate.

Why: Creditworthy point: increase the sample rate (1).

No marks0/1

Decrease the sample rate.

Why: Near-miss: decreasing the sample rate reduces accuracy, so no mark; the mark scheme's do-not-accept line covers this (0).

No marks0/1

Increase the volume of the sound.

Why: Misconception: loudness/amplitude is not a way to increase sampling accuracy; do not accept increase amplitude/volume (0).

2Short recall1 markImages Swap Remove

A bitmap image has a resolution.

State what is meant by the resolution of an image.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • The concentration/density of pixels in an area (1)
  • The number of pixels per inch (PPI) / pixels per unit area (1)
  • The width and height/dimensions of the image in pixels (1)

Do not accept the number of pixels in the image on its own, without dimensions or an area, e.g. 'the total number of pixels'

Do not accept colour depth / the number of bits used per pixel / the number of colours

Do not accept file size in bytes / the amount of storage the image uses / screen size / image quality

Example answers and how they were marked
Full marks1/1

The concentration of pixels in an area, such as the number of pixels per inch.

Why: Gives the density/concentration of pixels in an area, and pixels per inch (1)

No marks0/1

The number of pixels in the image.

Why: A bare total pixel count is not accepted without dimensions or an area

No marks0/1

The number of bits used to store each pixel's colour.

Why: Describes colour depth, not resolution, and colour depth is not accepted

3Explain2 marksSound Swap Remove

Analogue sound is converted to binary by sampling at regular intervals.

Explain one reason why increasing the sample rate improves the quality of a digitised sound.

[2 marks]
Mark scheme

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

  • More samples are taken every second / the sample rate is higher (1) so the digital wave follows the shape of the analogue wave more closely (1)
  • The amplitude is measured more often / at shorter intervals (1) so fewer changes in the sound are missed between measurements (1)
  • The sample interval is shorter (1) so less of the sound wave is lost/goes unrecorded between samples (1)
  • More data points are recorded for the same length of sound (1) so the digital representation is a closer copy of the original sound (1)

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

Do not accept 'the quality is better/higher' or 'the sound is clearer' as a point on its own without a reason such as more samples or more detail.

Do not accept 'the samples are more accurate' or 'more data is collected' without saying what becomes more accurate or what the extra data records.

Do not accept 'the file size is larger' as a reason for improved quality.

Do not accept answers about using more bits per sample, as these describe bit depth, not the sample rate.

Example answers and how they were marked
Full marks2/2

More samples are taken every second, so the digital representation follows the shape of the analogue wave more closely.

Why: Point (more samples each second) (1) with linked reason (follows the analogue wave more closely) (1).

Some marks1/2

More samples are taken every second.

Why: Creditworthy point (1) but no linked reason about what the extra samples achieve, so stays on one mark.

No marks0/2

Each sample is stored using more bits, so every measurement is more accurate.

Why: This describes bit depth, not the sample rate, so neither mark is awarded.

4Discuss6 marksImages Swap Remove

A school is creating a small logo to display on its website. The logo is stored as a bitmap image. Each pixel in the logo is stored as a binary value.

Discuss how the bitmap image of the logo is represented in binary.

Your answer should include:

  • pixels
  • binary values
  • the grid of pixels.
[6 marks]
Mark scheme

Indicative content

Pixels

  • A bitmap image is made up of picture elements, called pixels.
  • Each pixel is the smallest identifiable area of the image and has a single colour.
  • The logo is stored as a grid of pixels, and its width and height in pixels give its dimensions.
  • Each pixel is stored separately, so a larger grid needs more pixel values to be stored.

Binary values

  • Each pixel's colour is represented by a binary value.
  • The number of bits used for each pixel is the colour depth.
  • With n bits per pixel there are 2^n different binary values, so 2^n possible colours.
  • A black-and-white image can use one bit per pixel, with 0 for white and 1 for black.
  • More bits per pixel allow more colours to be represented in the logo.

Grid

  • The binary values are stored in order, row by row, so the computer can rebuild the grid.
  • The resolution is the number of pixels in the image, for example width × height.
  • A higher-resolution grid stores more pixels, so the logo can show more detail.
  • The image file stores the pixel values and data such as the image dimensions.

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 pixels and binary values.

Do not accept resolution as the number of colours.

Example answers and how they were marked
Full marks6/6

A bitmap is a grid of pixels. Each pixel is one small area of the logo and has a single colour. The width and height of the grid are measured in pixels, so the logo's dimensions tell us how many pixels it contains. Each pixel's colour is stored as a binary value. The number of bits used for each pixel is the colour depth, and with n bits there are 2^n possible values, so 2^n possible colours. For example, 3 bits per pixel would allow 8 colours. The binary values are stored row by row so that the computer can rebuild the grid. A larger grid stores more pixel values, but it can show more detail. More bits per pixel let the logo use more colours, such as the school's colours.

Why: Covers pixels as the smallest areas of a grid (AO1), binary values with colour depth and 2^n colours (AO1), and applies these to the logo's grid and colours (AO2). Sustained and structured, so Level 3.

Some marks4/6

A bitmap is a grid of pixels. Each pixel is a small square with one colour. Each pixel is stored as a binary value. The logo needs a binary value for every pixel, so a bigger logo has more values. More bits per pixel means more colours.

Why: Gives pixels and binary values, with a simple link to the logo's size. Points are mostly independent and not developed into a full discussion, so Level 2.

Some marks1/6

A bitmap image is a grid of pixels. Resolution is the number of colours in the image. Each pixel is stored as a letter, so the logo can use any colour.

Why: One basic point: a bitmap is a grid of pixels. The rest is incorrect: resolution is not the number of colours, and pixel values are stored as binary, not letters.

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