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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 · 5 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.

2Describe2 marksSound Swap Remove

A computer stores a digitised sound.

Describe how the sample rate affects the accuracy of the binary representation of a sound.

[2 marks]
Mark scheme

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

  • A higher sample rate means more samples are taken each second (1) so more binary values are stored to represent the sound (1)
  • A higher sample rate records the wave more frequently (1) so the binary representation follows the shape of the analogue wave more closely/is more accurate (1)
  • A lower sample rate records fewer samples (1) so the binary representation is less detailed/less accurate (1)

A statement about the effect of sample rate on sampling (e.g. more/fewer samples) without a link to the binary representation scores a maximum of one mark.

A definition of sample rate on its own, with no effect on sampling, scores no marks.

Accept 'more accurate' for the second mark only when linked to more samples or binary values being stored, for example by 'so', 'which means' or 'because'.

Do not accept responses that describe sample interval or bit depth instead of sample rate.

Do not accept 'a higher sample rate means more bits per sample' or 'higher resolution', as these describe bit depth.

Do not accept a larger file size unless it is linked to more samples/binary values being stored.

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

Example answers and how they were marked
Full marks2/2

A higher sample rate takes more samples each second, so more binary values are stored and the digital representation is more accurate.

Why: Linked points: more samples each second (1) leading to more binary values and a more accurate representation (1).

Some marks1/2

A higher sample rate records the wave more often.

Why: Correct statement about the effect on sampling (1) but no link to the binary representation.

No marks0/2

A higher sample rate uses more bits for each sample, so each sample is more accurate.

Why: Confuses sample rate with bit depth; 'more bits per sample' is not accepted.

3Explain2 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.

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