Keywords and Identifiers

Keywords :

Keywords are the reserved words which convey some special meaning for compiler.

  • They cannot be changed or manipulated by user.
  • They are case sensitive.
  • There are 32 keyword in C


Identifiers :

  • Identifiers are the name given to the tokens used by a user.
  • Token is the smallest unit in program.
  • Identifiers are case sensitive.
  • They are defined by programmer.


  • It must not be a keyword
  • Identifiers can only have alphabets, numbers and an underscore sign( _ ).
  • It should not begin with a numbers.
  • Identifiers can be any characters long.


Valid Identifiers :

My_name, myname, myNAME, my123, my_123, m12_n32, m1n2 etc.

Invalid Identifiers:

12Myname, 123, #myname, ?myname, int.

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