C Identifiers

During execution of the program, you may require a container (variable) to hold input or output or an intermediate value.
These values are stored in computer’s memory at a different memory locations. To refer these memory locations, we need to use identifier.

What is identifier?

Identifiers is a name that is given to various program elements such as variables, symbolic constants, functions, structures or enums. The identifier is used to identify a user-defined item.


In the above examples int, char, double are keywords whereas marks, name, total are identifiers.

Rules for Naming C Identifiers

  • An identifier can only start with letter (A-Z, a-z) or underscore( _ ) symbol.
  • An identifier can contain alphabet, digits(0-9), and underscore only.
  • The identifier must not contain white spaces.
  • A keyword can not use as an identifier.
  • You can not use punctuation characters (@, #, $, %, &) as identifers.
  • As C is a case-sensitive language. Thus, MARKS, Marks, marks are different identifiers.
  • So identifier name should be unique.
  • Length of an identifier can contain 31 characters.


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