Source-coding definitions

• A code is a function ?: X ? B+

  • B = {0, 1}
  • B+ ? the set of finite strings over B
    • B+ = {0, 1, 00, 01, 10, 11, 000, 001, …}
  • ?(x) = ?(x1) ?(x2) ?(x3) … ?(xN)

• A code is uniquely decodable (UD) iff

  • ?: X+ ? B+ is one-to-one

• A code is instantaneous iff

  • No codeword is the prefix of another
  • ?(x1) is not a prefix of ?(x2)

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