Identifiers are the names that are given to various program elements such as variables, symbolic constants and functions. Variable or function identifier that is called a symbolic constant name.

Identifier can be freely named, the following restrictions.

  • Alphanumeric characters (a ~ z, A~Z, 0~9) and half underscore ( _ ) can only be used.
  • The first character of the first contain letters ( a ~ z , A~Z ) or half underscore ( _ ) can only be used.
  • Case is distinguishable. That is, word and WORD is recognized as a separate identifier.
  • Reserved words are not allowed. However, part of an identifier reserved words can be included.

Here are the rules you need to know :

  • Identifier name must be a sequence of letter and digits, and must begin with a letter.
  • The underscore character (‘_’) is considered as letter.
  • Names shouldn't be a keyword. (such as int , float, if ,break, for etc)
  • Both upper-case letter and lower-case letter characters are allowed. However, they're not interchangeable.
  • No identifier may be keyword.
  • No special characters, such as semicolon, period, blank space, slash or comma are permitted.