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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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4 questions · 5 marks

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1Multiple choice1 markCharacter Sets Swap Remove

Characters are encoded using 7-bit ASCII.

Identify the number of different characters that can be represented using 7-bit ASCII.

[1 mark]
  • A64
  • B127
  • C128
  • D256
Mark scheme
  • C 128 (1)
  • The only correct answer is C. The correct answer is 128.
  • A is not correct because 6 bits give only 64 different combinations
  • B is not correct because 127 is the largest 7-bit value, not the number of characters that 7 bits can represent
  • D is not correct because 256 characters need 8 bits, as used by 8-bit extended ASCII
Example answers and how they were marked
Full marks1/1

C 128

Why: Selects the only correct option (1): 7 bits give 2 to the power of 7, which is 128 different characters.

No marks0/1

D 256

Why: Near miss scoring 0: 256 is the number of characters that 8 bits give in extended ASCII, not 7-bit ASCII.

No marks0/1

B 127

Why: Misconception scoring 0, the off-by-one error the examiners' report describes: 127 is the largest 7-bit value, but 7 bits give 128 different characters.

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 markImages Swap Remove

A bitmap image uses one bit per pixel.

State the limitation this places on the number of colours in the image.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • Only two different colours can be represented/stored (1)
  • Each pixel can only be one of two values (1)
  • The image can only be shown in black and white (1)

Allow answers that give the number of colours, e.g. two colours, 2 colours

Allow any pair of two colours, e.g. black and white, black and grey

Do not accept low resolution/poor quality/lower quality

Do not accept only one colour/can only show black

Do not accept 2 bits/2^1 without a statement about the number of colours that can be represented

Example answers and how they were marked
Full marks1/1

Only two colours can be represented, such as black and white.

Why: States that only two different colours can be represented (1)

No marks0/1

The image will have a low resolution.

Why: Confuses colour depth with resolution; low resolution is not accepted

No marks0/1

The image can only show black.

Why: One colour is all a single value can give; the limitation is that only two colours can be represented, so this is not accepted

4Describe2 marksCharacter Sets Swap Remove

Uppercase letters are represented in a computer using 7-bit ASCII codes.

Describe how the ASCII codes for the uppercase letters A to Z are arranged.

[2 marks]
Mark scheme

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

  • The codes run in alphabetical order/consecutively (1) so each letter has a code one more than the letter before it (1)
  • A has the code 65 and Z has the code 90 (1) so the codes for the letters in between increase by 1 each time (1)
  • The letters are stored in sequence (1) so B is A + 1, C is B + 1 and so on (1)

Accept the codes given in denary (65, 90) or as 7-bit binary (1000001, 1011010).

Do not accept 'the codes go up' or 'the codes are in order' on its own, as neither gives the step of 1 or links one letter to the next.

Do not accept 'each uppercase letter has a different code' on its own, as this does not describe the arrangement.

Example answers and how they were marked
Full marks2/2

The codes are in alphabetical order, so B is one more than A and C is one more than B.

Why: Codes are consecutive/in order (1) with the linked step of one more for each letter (1).

Some marks1/2

A is 65 and Z is 90.

Why: Gives the first half of the linked pair, the start and end codes (1), but does not give the linked development, the increase of 1 between letters (0).

No marks0/2

The ASCII codes for uppercase letters go up.

Why: 'Codes go up' on its own gives no step of 1 and no link to the next letter, so it is not creditworthy (0) under the 'Do not accept' line.

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