Lesson 4.5.5.1

4.5.5.1 Character codes, ASCII and Unicode Quiz: AQA Computer Science, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.5.5.1, Character codes, ASCII and Unicode: 20 multiple choice questions for the AQA Computer Science (7517), Unit 5: Fundamentals of data representation, written with Revision Ninja.

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The 20 questions

  1. What is the ASCII code, in decimal, for the uppercase letter 'A'?

    • 66
    • 65
    • 48
    • 97

  2. Which character code was introduced to support characters from all of the world's languages?

    • Binary coded decimal
    • ASCII
    • Unicode
    • Gray code

  3. How many bits does standard ASCII use for each character?

    • 32 bits, giving about 4 billion characters
    • 7 bits, giving 128 possible characters
    • 4 bits, giving 16 possible characters
    • 16 bits, giving 65,536 possible characters

  4. Which description of ASCII is most accurate?

    • A code that stores each digit in binary coded decimal, with four bits for every decimal digit
    • An 8-bit code covering every language in the world, including every script in current use
    • A compression scheme for large text files, which removes repeated characters before storage
    • A 7-bit character code covering English letters, digits, punctuation and control characters

  5. What is the character form of a decimal digit such as 7?

    • The character code for the symbol '7', which is a different bit pattern from binary 0111
    • The binary value 0111, which is the same as its character code because the code is pure binary
    • The value 7 stored as an 8-bit integer only, which is the same pattern as its character code
    • The Gray code of the number 7, which is a single-bit change from the binary value of six

  6. What is the ASCII code, in decimal, of the character '0'?

    • 32
    • 48
    • 1
    • 0

  7. Which decimal value is the ASCII code for the lowercase letter 'a'?

    • 98
    • 122
    • 65
    • 97

  8. The character '7' has ASCII code 55. What is 55 in 7-bit binary?

    • 0110111
    • 0111000
    • 0000111
    • 0110110

  9. How many bytes does the ASCII text 'Quiz' need, using one byte per character?

    • 3 bytes
    • 16 bytes
    • 8 bytes
    • 4 bytes

  10. A file stores 1000 characters, each using 16 bits. How many bytes does the file need?

    • 8000 bytes
    • 4000 bytes
    • 2000 bytes
    • 1000 bytes

  11. The ASCII code for 'A' is 65. What is the ASCII code for 'C'?

    • 68
    • 66
    • 67
    • 70

  12. What is the ASCII code of the character '9', and how does it differ from the binary value 9?

    • ASCII '9' is 1001, because digits share their binary values
    • ASCII '9' is 90, while binary 9 is 1001
    • ASCII '9' is 57, which is 0111001, while binary 9 is 1001
    • ASCII '9' is 9, so both have the bit pattern 1001

  13. A text uses 200 ASCII characters, each stored in 7 bits. How many bits are needed?

    • 200
    • 800
    • 1600
    • 1400

  14. A string of 10 characters is stored with 8 bits per character. How many bits does it need?

    • 100
    • 80
    • 70
    • 10

  15. How many distinct characters can an 8-bit code represent?

    • 256
    • 128
    • 255
    • 64

  16. Why does Unicode need more than one byte for some characters?

    • Unicode stores characters as decimal digits, which need more space than binary codes in a file
    • Unicode codes are the same as ASCII codes, so no extra bits are needed for any character set
    • Unicode uses only four bits, so it is always smaller than ASCII for every text in every language
    • One byte gives only 256 codes, far fewer than the characters across all scripts, so longer codes are needed

  17. A text file has 500 characters. 480 are ASCII characters stored in 1 byte each and 20 are stored in 2 bytes each. What is the total size?

    • 540 bytes
    • 1000 bytes
    • 500 bytes
    • 520 bytes

  18. Which pair of ASCII codes differ by exactly 32 for an uppercase and lowercase letter?

    • 'a' (97) and 'z' (122)
    • 'A' (65) and 'B' (66)
    • 'A' (65) and 'a' (97)
    • '0' (48) and 'A' (65)

  19. The ASCII code of the character '4' is 52. What value results from subtracting 48?

    • 3
    • 4
    • 48
    • 52

  20. Which statement about the ASCII codes of 'Z' (90) and 'z' (122) is correct?

    • The difference is 90, which is the value of 'Z' and so the two codes differ by its size
    • The difference is 32, the same as between any uppercase letter and its lowercase counterpart
    • The difference is 25, so the two codes are unrelated and the lowercase letter is stored separately
    • 'z' needs fewer bits than 'Z' in standard ASCII, because lowercase letters use a smaller code range

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