Edexcel GCSE Computer Science (1CP2) exam questions

Build a practice paper from 514 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.

Practice paper

8 questions · 16 marks

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1Multiple choice1 markCharacter Sets Swap Remove

A new character set must be able to represent 70 different characters.

Identify the minimum number of bits needed to represent each character.

[1 mark]

Mark scheme

B 7 (1)
The only correct answer is B. The correct answer is 7.
A is not correct because 6 bits give only 64 combinations, which is not enough for 70 characters
C is not correct because 7 bits already give 128 combinations, so 8 bits is not the minimum needed
D is not correct because 70 is the number of characters needed, not a number of bits

Example answers and how they were marked

Full marks1/1

B 7

Why: The only correct answer: 7 bits give 128 combinations, enough for 70 characters, and it is the smallest number of bits that does (1).

No marks0/1

C 8

Why: Distractor, no credit: a single-tick item has no partial credit, and 8 bits is not the minimum because 7 bits already give 128 combinations, so the scheme's C line gives no mark.

No marks0/1

A 6

Why: Misconception, no credit: 6 bits give only 64 combinations, which cannot represent 70 different characters, so the scheme's A line gives no mark.

2Short 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.

3Short 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).

4Short 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

5Explain2 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 (1) so each pixel represents a smaller part of the image (1).

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.

6Explain2 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.

7Explain2 marksSound Swap Remove

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

Explain how increasing the bit depth affects the representation of a sound wave.

[2 marks]

Mark scheme

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

Each sample is stored using more bits (1) so the amplitude can be recorded more precisely (1)
More different amplitude values can be represented (1) because each extra bit doubles the number of possible values (1)
The height of the wave at each sample point is measured more accurately (1) so the digital wave is closer to the analogue wave (1)
The gap between the true amplitude and the stored value is smaller (1) because there are more values for the sample to be rounded to (1)

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

Do not accept 'the sound is sampled more often' or 'more samples are taken per second', as these describe the sample rate, not the bit depth.

Do not accept 'the file size increases' on its own as an effect on the representation of the sound.

Example answers and how they were marked

Full marks2/2

Each sample is stored using more bits, so the amplitude at each sample point can be recorded more precisely.

Why: Point (more bits per sample) (1) with linked reason (amplitude recorded more precisely) (1).

Some marks1/2

Each sample is stored using more bits.

Why: Creditworthy point (1) but no linked effect on the accuracy of the representation, so only one mark.

No marks0/2

It takes more samples every second, so the wave is stored in more detail.

Why: Confuses bit depth with sample rate, so no mark is awarded.

8Discuss6 marksCharacter Sets Swap Remove

A library is digitising its catalogue. The titles of books and the names of authors are stored as text.

Discuss how 7-bit ASCII is used to encode the text in the library catalogue.

Your answer should include:

how characters are mapped to codes
why 7 bits are used for each character
the benefits of using ASCII for the catalogue.

[6 marks]

Mark scheme

Indicative content

How characters are mapped to codes

Each character in a book title or author name is given a unique 7-bit binary code from the ASCII character set.
The letter A, for example, is stored as the code 1000001 and the letter B as 1000010, so the catalogue can store letters as binary.
Uppercase letters, lowercase letters, digits, punctuation and the space character each have their own ASCII code.
The same character always uses the same code, so the text can be stored and read back correctly by the library system.

Why 7 bits are used for each character

Seven bits give 2 to the power of 7, which is 128 different bit patterns, and this is enough to represent the letters, digits and punctuation needed in the catalogue.
A standard keyboard has around 98 characters, so 6 bits would give only 64 codes and would not be enough.
Using a fixed 7 bits per character means every character takes the same amount of storage, which makes the catalogue file simple to process.

Benefits of using ASCII for the catalogue

ASCII is a standard character set, so the catalogue data can be exchanged between different computers and software.
Author names and titles entered on one system will display correctly on another system that uses ASCII.
ASCII uses only 7 bits per character, so the catalogue takes less storage than a character set that uses more bits.
It is simple to encode and decode because each character has a single fixed code.

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)

Do not accept 8 bits or 256 characters as features of 7-bit ASCII; these are extended ASCII.

Example answers and how they were marked

Full marks6/6

Each character in a catalogue title or author name is given its own 7-bit ASCII code. For example, the letter A is 1000001 and the letter B is 1000010, so the library can store the text as binary. Seven bits give 128 different codes, which is enough for uppercase and lowercase letters, digits, punctuation and spaces. Six bits would give only 64 codes, which would not be enough for all the characters in the catalogue. ASCII is also a standard character set, so the catalogue data can be exchanged between different computers and will display correctly. Because each character uses only 7 bits, the catalogue also takes less storage than it would with a character set that uses more bits per character.

Why: Covers all three bullets with sustained application: mapping and example codes; 7 bits give 128 codes and why 6 bits is insufficient; standardisation and storage benefits. Level 3.

Some marks4/6

ASCII gives each character a unique code. For example, A is stored as 1000001 and B is stored as 1000010. Seven bits are used for each character because seven bits give 128 codes, which is enough for the letters and punctuation in the catalogue. The library can store titles and author names as binary.

Why: Covers mapping and the 7-bit reason with some application, but does not discuss the benefits of ASCII for the catalogue. Level 2.

Some marks1/6

ASCII is a programming language that gives each letter a binary code. It uses 8 bits for each character, so it can store 256 characters. This means it can store every book title in the library.

Why: A basic point that letters are given binary codes is credited, but the answer treats ASCII as a programming language and uses 8 bits/256 characters, which are misconceptions. Level 1.

Edexcel GCSE Computer Science (1CP2) Exam Questions

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Questions by topic

2.1 Binary

2.2 Data representation

2.3 Data storage and compression

3.1 Hardware

3.2 Software

3.3 Programming languages

4.1 Networks

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