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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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3 questions · 4 marks

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1Short recall1 markSound Swap Remove

Digital sound is made up of samples.

Define the term 'bit depth'.

[1 mark]
Mark scheme

Award one mark for:

  • The number of bits used per sample (1)

Allow bits per sample

Allow the number of bits used to record/store each sample

Do not accept the number of samples taken per second (sample rate)

Do not accept the number of bits used to store the whole sound file

Do not accept the number of levels/amplitude values a sample can take

Example answers and how they were marked
Full marks1/1

The number of bits used to record each sample.

Why: States the number of bits per sample (1).

No marks0/1

The number of samples taken each second.

Why: Defines sample rate, not bit depth; do not accept.

No marks0/1

The number of amplitude values each sample can take.

Why: Gives the number of levels/amplitude values, not the number of bits per sample; do not accept.

2Short recall1 markImages Swap Remove

Each pixel in a bitmap image is stored using a number of bits.

Define the term colour depth.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • The number of bits per pixel (1)
  • The number of bits used to represent/store the colour of each pixel (1)

Allow bit depth

Do not accept the number of colours a pixel can have on its own

Do not accept the number of pixels in the image (this is the resolution/image size)

Example answers and how they were marked
Full marks1/1

The number of bits used to store the colour of one pixel.

Why: Gives the number of bits per pixel (1)

No marks0/1

The number of colours that each pixel can use.

Why: Gives the number of colours, not the number of bits; the mark scheme does not accept this on its own

No marks0/1

The number of pixels in the image.

Why: Confuses colour depth with resolution/image size, which the mark scheme does not accept

3Describe2 marksImages Swap Remove

A bitmap image is stored using 2 bits for each pixel.

Describe why using 2 bits for each pixel can limit the image.

[2 marks]
Mark scheme

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

  • Two bits give only four possible binary values (1) so at most four colours can be represented (1)
  • Only 2^2 = 4 colours can be stored (1) so colours in the original image may be lost/changed (1)
  • There are not enough bit patterns for more than four colours (1) so the image cannot show all the colours it needs (1)
  • Each pixel has a limited set of codes (1) so similar colours may become the same colour (1)

Do not accept 'the image will be low resolution' or 'it will be poor quality' alone.

Do not award responses about file size.

Example answers and how they were marked
Full marks2/2

Two bits give only four binary values, so the image can use at most four colours.

Why: Point (1) that two bits give only four binary values and development (1) that at most four colours can be represented.

Some marks1/2

Two bits can only represent four colours.

Why: Point (1) that only four colours can be stored, but no linked development about colours being lost or changed.

No marks0/2

The image will be low resolution because there are not enough bits.

Why: No credit: 'low resolution' alone is not accepted as a limitation of using 2 bits per pixel.

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