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Backus Normal Form

What Does Backus Normal Form Mean?

Backus Normal Form (BNF) is a metasyntactic notation procedure used to specify the syntax of computer programming languages, command/instruction sets, document formatting and communication protocols. BNF is applied when language descriptions are required.


BNF is also known as Backus-Naur form.

Techopedia Explains Backus Normal Form

A BNF specification is a derivation rule set that is usually written as follows:

  • The <symbol>::_expression_where <symbol> is a non terminal
  • The _expression_consists of one or more symbol sequences.
  • A vertical bar (|) delineates other sequence options.
  • Symbols not appearing on the left side are terminals.
  • Symbols appearing on the left side are located within the symbol-expression pair and are non-terminals.

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