Encoding of Information

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  • In computers, encoding is the process of putting a sequence of characters (letters, numbers, punctuation, and certain symbols) into a specialized format for efficient transmission or storage.
  • Decoding is the opposite process -- the conversion of an encoded format back into the original sequence of characters.
  • Encoding and decoding are used in data communications, networking, and storage.
  • The code used by most computers for text files is known as ASCII (American Standard Code for Information Interchange).
  • ASCII can depict uppercase and lowercase alphabetic characters, numerals, punctuation marks, and common symbols.
  • Other commonly-used codes include Unicode, BinHex and Uuencode.
  • In data communications, Manchester encoding is a special form of encoding in which the binary digits (bits) represent the transitions between high and low logic states.

Operation Code (Opcode)


  • It specifies the operation to be performed.
  • The operation of the CPU is determined by the instructions it executes.
  • The instructions are referred to as machine instructions or computer instructions.
  • Each instruction must contain the information required by the CPU for execution.

Encoding and decoding

  • It is important that the opcode word be easy to decode.
  • A decoder that must examine a large number of opcode bits simultaneously requires a correspondingly large number of levels of logic gates and introduces a large delay.
  • If the opcode is divided into small fields and a separate decoder is used for each field, the decoding delay will be much smaller.
  • Three formats are used for data manipulation instructions and the fourth is used in flow control instructions such as branch and branch-to-subroutine.
  • The opcode field also determines certain units which will be responsible for completing the execution of the instruction and so should read the information on the source buses.

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