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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 659 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 · 7 marks

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1Short recall1 markSound Swap Remove

To store sound in binary, an analogue sound wave is sampled at regular intervals.

Define the term 'sample rate'.

[1 mark]
Mark scheme

Award one mark for:

  • The number of samples taken per second (1)

Allow captured/recorded for taken.

Allow 'samples per second'.

Allow 'each second' for 'per second'.

Allow Hz/hertz as the unit.

Do not accept the time between samples/sample interval.

Do not accept 'the number of samples' without a per second/time reference.

Do not accept the number of bits used per sample/bit depth.

Example answers and how they were marked
Full marks1/1

The number of samples taken per second.

Why: States samples per second (1); 'per second' is accepted.

No marks0/1

The time between each sample.

Why: Defines sample interval, not sample rate; do not accept.

No marks0/1

The number of bits used for each sample.

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

2Describe2 marksCharacter Sets Swap Remove

A computer uses 7-bit ASCII to store text.

Describe why 7 bits are needed to represent each character, rather than 6 bits.

[2 marks]
Mark scheme

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

  • 6 bits give only 64 different codes (1) which is fewer than the number of letters, digits and symbols that must be represented (1)
  • 7 bits give 128 different codes (1) which is enough to represent every letter, digit and symbol that is needed (1)
  • Adding a bit doubles the number of different codes from 64 to 128 (1) so that every character needed can have its own code (1)
  • There are more than 64 characters that must be represented (letters, digits and symbols) (1) so 6 bits cannot give each one a different code (1)

A statement of the number of codes without a development can earn one mark only; the development must be linked to the statement for the second mark.

Do not accept responses that only say computers use binary (1s and 0s).

Do not accept that 7 bits are needed because 7 is a bigger number than 6, with no reference to the number of codes or characters.

Do not accept responses about 8 bits, extended ASCII or Unicode.

Example answers and how they were marked
Full marks2/2

6 bits can only give 64 different codes, which is not enough for all the letters, digits and symbols that have to be represented.

Why: Gives the number of codes 6 bits can make (1) linked to the number of characters that must be represented (1).

Some marks1/2

7 bits give 128 different codes.

Why: States the number of codes available from 7 bits (1) but gives no linked development, so the second mark is not earned (0).

No marks0/2

Because computers only use binary and 7 is a bigger number than 6.

Why: Says only that computers use binary and compares the numbers, which the mark scheme tells markers not to accept; no creditworthy point about codes or characters.

3Explain2 marksImages Swap Remove

A bitmap image uses a colour depth of 8 bits. Each pixel is stored as a binary value.

Explain how the colour of a pixel is represented in a bitmap image.

[2 marks]
Mark scheme

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

  • Each pixel is stored as a binary value/code (1) which represents/maps to a colour (1)
  • The binary value is used to look up a colour in a palette (1) so the pixel can be displayed in that colour (1)
  • A bit pattern is assigned to each colour (1) and each pixel stores the bit pattern for its colour (1)
  • The number of bits per pixel sets how many different colour codes exist (1) so each code can represent a different colour (1)

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

Do not accept 'pixels are binary' or 'the image is made of 1s and 0s' without saying a pixel's colour is represented by a binary value.

Do not accept RGB values stored as denary or hexadecimal.

Example answers and how they were marked
Full marks2/2

Each pixel stores a binary value; this value is used to look up the pixel's colour in a palette.

Why: Linked point (1) and reason (1): a binary value is stored for each pixel and maps to a colour.

Some marks1/2

A bit pattern is assigned to each colour.

Why: One mark for stating that colours have bit patterns; it does not say that each pixel stores the pattern for its colour.

No marks0/2

Each pixel stores the RGB colour as denary numbers between 0 and 255.

Why: Bitmap pixels are stored in binary, not as denary values; this common misconception earns no mark.

4Explain2 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.

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5.3 Cybersecurity

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