GCSE Computer Science (CCEA)

Topic Summaries

COMPUTER SYSTEMS: Encoding and compression

Characters

  • A character set is a table that gives each symbol or letter a binary code.
  • ASCII: 7 or 8-bit codes for basic English letters/symbols (e.g. A = 01000001, B = 01000010). This allows for 128 possible characters – mainly English letters, digits, and basic punctuation).
  • Unicode: is much bigger than ASCII and supports many languages and symbols (e.g. Chinese characters, Arabic script, emojis) using more bits, typically 16, 32, or variable-length encoding like UTF-8. 
    • UTF-8 is a popular Unicode encoding that remains compatible with ASCII for standard English text while allowing extra bytes for more complex characters. 
    • Using Unicode enables global text processing, ensuring consistency and compatibility across platforms and languages.

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