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Information coding systems
Official AQA 7517 section 4.5.5.
0
Objectives
10
Flashcards
10
Questions
76 min
Study time
AqaA LevelComputer ScienceFundamentals of data representation
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Character form of a decimal digit1 objectives
- Character form of a decimal digit: Differentiate between the character code representation of a decimal digit and its pure binary representation. 68
ASCII and Unicode1 objectives
- ASCII and Unicode: Describe ASCII and Unicode coding systems for coding character data and explain why Unicode was introduced.
Error checking and correction1 objectives
- Error checking and correction: Describe and explain the use of: • parity bits • majority voting • checksums • check digits.
Key terms
Character codePure binary representationCharacter coding systemUnicodeChecksumCheck digit
Exam tips
- State the meaning, not just the bit pattern: When comparing representations, explicitly say whether the bits represent a character or a numerical value.
- Link the limitation to the reason for Unicode: When explaining why Unicode was introduced, explicitly connect ASCII's limited character set to the need to represent characters from more languages and additional symbols.
Common mistakes
- Assuming a digit character is the same as its value: Identify whether the data is text or a number. A character code for '7' represents the character; the numerical value 7 has its own pure binary representation.
- Confusing ASCII's bit length with Unicode: State that standard ASCII uses 7 bits and has a limited character set. Unicode was introduced to support a much wider range of characters.
Practice preview
- A system uses the character code 00110100 for the character '4'. Which is the pure binary representation of the numerical value four?
- A user enters the two-character sequence '27'. Which statement is correct?
- Which statement best differentiates the character code representation of a decimal digit from its pure binary representation?
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