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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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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.

2Describe2 marksCharacter Sets Swap Remove

A school needs to store text in several different languages.

Describe one limitation of using 7-bit ASCII to store this text.

[2 marks]
Mark scheme

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

  • 7-bit ASCII has only 128 different codes (1) so characters from languages such as Chinese cannot be stored (1)
  • 7 bits give 2^7 = 128 possible binary codes (1) so there are not enough codes to give every character in the world's languages its own code (1)
  • Only the 128 characters in the ASCII set can be stored (1) so a character outside the set, such as é or 中, cannot be represented (1)

The stated limit on its own (that ASCII can represent only 128 characters) earns 1 mark; the second mark is for linking it to characters from other languages not being storable.

Do not accept 'ASCII can only store English letters/characters' unless it refers to the 128 codes or the 7 bits.

Do not accept a statement that ASCII is 'limited' or 'old' with no link to the number of bits/codes.

Do not accept a recommendation to use Unicode instead, or that ASCII cannot store accented letters, without saying that the 7 bits/128 codes cause the limitation.

Do not accept responses that describe ASCII as a programming language.

Example answers and how they were marked
Full marks2/2

7-bit ASCII can only represent 128 characters, so it cannot store characters from languages such as Chinese.

Why: Only 128 characters/codes can be represented (1) and this is linked to characters from other languages not being storable (1).

Some marks1/2

ASCII only has 128 characters.

Why: States the limit set by the 7 bits, that only 128 characters can be represented (1), but does not link it to the text in several languages (0).

No marks0/2

ASCII can only store English letters, so the school should use Unicode to store accented letters like e with an accent.

Why: 'Only stores English letters' is not accepted without reference to the 128 codes/7 bits, and recommending Unicode is not a limitation caused by the number of available bits.

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.

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