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Edexcel GCSE Computer Science (1CP2) Exam Questions

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5 questions · 9 marks

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1Multiple choice1 markCharacter Sets Swap Remove

A text file stores each character using 7-bit ASCII.

Identify the denary ASCII code for the space character.

[1 mark]
  • A32
  • B33
  • C48
  • D65
Mark scheme
  • A 32 (1)
  • The only correct answer is A. The correct answer is 32.
  • B is not correct because 33 is the ASCII code for the exclamation mark (!)
  • C is not correct because 48 is the ASCII code for the character 0
  • D is not correct because 65 is the ASCII code for the uppercase letter A
Example answers and how they were marked
Full marks1/1

A 32

Why: Correct option: the space character has the ASCII code 32 (1).

No marks0/1

C 48

Why: Near miss scoring 0: 48 is the ASCII code for the character 0, not the space character.

No marks0/1

D 65

Why: Misconception scoring 0: 65 is the ASCII code for the uppercase letter A, so a well-known code is given but not the code for a space.

2Short recall2 marksSound Swap Remove

A sound wave is sampled and the amplitude of each sample is stored using a small number of bits.

Give two limitations of storing the sound in binary when only a small number of bits is available for each sample.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • Only a limited/fixed number of amplitude values can be stored (1)
  • The amplitude of each sample is rounded/approximated to the nearest value that can be stored (1)
  • The recording is less accurate than the original analogue sound/does not match the analogue wave exactly (1)
  • Sounds louder than the highest amplitude that can be stored are clipped/distorted (1)
  • Sounds quieter than the lowest amplitude that can be stored cannot be represented/are lost (1)

Allow quantisation error/noise for the amplitude being rounded to the nearest value that can be stored, but do not award a second mark for the same idea

Allow a stated consequence as a separate mark only when it is a different point from the list, e.g. fewer amplitude values can be stored (1) so very quiet sounds are lost (1)

Do not accept 'lower quality'/'poorer sound' on its own; the answer must say the recording is less accurate than the original/does not match the analogue wave

Do not accept sample rate/sample interval/number of channels (stereo/mono), as these are not limited by the number of bits available for each sample

Do not accept remedies such as 'a larger bit depth would make it more accurate', as these do not describe a limitation

Do not accept answers about file size, compression or playback method

Do not accept a statement that repeats the stem, e.g. 'the sound is stored in binary using a fixed number of bits'

Example answers and how they were marked
Full marks2/2

The amplitude of each sample has to be rounded to the nearest value that can be stored, and very quiet sounds cannot be represented.

Why: Amplitude rounded to the nearest stored value (1) and quiet sounds cannot be represented (1): two different points from the list.

Some marks1/2

The recording is less accurate than the original sound.

Why: The recording is less accurate than the original analogue sound (1); a second, different limitation is not given.

No marks0/2

The sample rate is too low, so parts of the wave are missed.

Why: Sample rate is not limited by the number of bits per sample, so it is not accepted.

3Describe2 marksSound Swap Remove

Sound is converted into binary using a limited bit depth.

Describe one limitation of representing a sound sample with a limited bit depth.

[2 marks]
Mark scheme

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

  • Only a fixed number of amplitude values/levels can be represented (1) so the amplitude is rounded to the nearest available value/level (1)
  • Fewer amplitude values/levels are available to choose from (1) so similar/close amplitudes cannot be stored as different values (1)
  • The exact amplitude often falls between available values/levels (1) so the stored amplitude is not exact/less accurate (1)

Answers must relate to the number of bits per sample (bit depth) and the amplitude values/levels it can represent.

Do not accept answers about the sample rate, sample interval or the number of samples taken, or that confuse bit depth with the number of samples.

Do not award 'lower quality'/'more detail'/'less detail' unless it is linked to the number of amplitude values/levels.

Do not accept 'the sound cannot be played/stored' without a linked limitation.

Example answers and how they were marked
Full marks2/2

Only a fixed number of amplitude values can be represented, so the amplitude is rounded to the nearest available value and some detail is lost.

Why: Linked points: fixed number of amplitude values (1) and rounding to the nearest available value (1).

Some marks1/2

Only a fixed number of amplitude values can be represented.

Why: Gives the first linked point only (1); it does not develop what this limitation leads to.

No marks0/2

A lower bit depth means fewer samples are taken, so parts of the sound are missed.

Why: Confuses bit depth with the number of samples/sample rate; no creditworthy point about amplitude values is given.

4Explain2 marksCharacter Sets Swap Remove

Characters typed on a keyboard are stored using ASCII.

Explain how the computer encodes the letter A using ASCII.

[2 marks]
Mark scheme

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

  • The computer looks up the character in the ASCII character set/table (1) to find the code that represents it (1)
  • Each character has its own unique ASCII code (1) so the letter A is converted to and stored as a 7-bit binary pattern (1)
  • ASCII uses 7 bits for each character (1) so A is stored as its ASCII code 1000001 (binary) / 65 (denary) (1)

The second mark requires a linked expansion, so a point on its own (e.g. 'A has the code 65') can only earn one mark.

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

Accept an 8-bit pattern with a leading 0 (e.g. 01000001) as the binary code for A.

Do not accept 'the character is stored as text' without saying it is changed into a code/binary.

Do not accept a binary value on its own (e.g. 1000001) without saying that it is the ASCII code/that the character is converted to it.

Example answers and how they were marked
Full marks2/2

The computer finds the unique ASCII code for A, which is 65 in denary, and stores it as the 7-bit binary pattern 1000001.

Why: Linked point that A is given its unique ASCII code (1) and reason/expansion that it is converted to and stored as a 7-bit binary pattern (1).

Some marks1/2

The computer changes the letter A into a number.

Why: Gives the point that the character is given a code/number (1) but no linked expansion saying it is converted to binary or stored, so stays on one mark.

No marks0/2

The letter A is stored as the number 1 because it is the first letter of the alphabet.

Why: Wrong reason and no creditworthy point: it does not say that the character is given its ASCII code and converted to binary.

5Explain2 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 (1); this value is used to look up the pixel's colour in a palette (1).

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.

Questions by topic

2.1 Binary

Build a paper on this topic 58
Adding Binary Numbers 6 questions Binary and Hexadecimal Basics 10 questions Binary Shifts 6 questions Binary to Denary Conversion 6 questions Binary to Hexadecimal Conversion 6 questions Denary to Binary Conversion 6 questions Denary to Hexadecimal Conversion 6 questions Denary to Negative Binary Conversion 6 questions Hexadecimal to Binary Conversion 6 questions

2.2 Data representation

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Character Sets 18 questions Images 19 questions Sound 19 questions

2.3 Data storage and compression

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Compression 18 questions Units & Conversion 6 questions

3.1 Hardware

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Embedded Systems 17 questions Fetch Decode Execute Cycle 15 questions Primary Memory 15 questions Secondary Memory 15 questions Stored Program Computers 15 questions

3.2 Software

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File Management 18 questions Memory Management 16 questions Peripheral Management 11 questions Process Management 12 questions Purpose & Function of Operating Systems 17 questions Software Basics 13 questions User Management 18 questions Utility Software 19 questions

3.3 Programming languages

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Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

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Addressing 16 questions LANs & WANs 16 questions Network Speed 5 questions Packet Switching 16 questions Protocols & Layers 17 questions The Internet 16 questions Topologies 17 questions Wired Connections 17 questions Wireless Connections 18 questions

4.2 Network security

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Network Security Risks 18 questions Preventing Network Security Risks 18 questions

5.1 Environmental

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E-waste 17 questions Manufacturing Technology 19 questions

5.2 Ethical and legal

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Data Protection Act 17 questions Impact of AI 16 questions Intellectual Property 12 questions

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