Identifiers refer to the names of variables, constants, functions and arrays. They are user defined names and consist of sequence of letters or digits. Both lowercase and uppercase letters can be used as identifiers. Identifiers are of variable length. Underscore character is also permitted in identifiers. Example : max,s234, no_of_days.


Every C word is classified as an identifier or a keyword. All keywords have fixed meanings and these meanings cannot be changed .Keywords serve as building blocks of a program statements .they can be used for user defined words. There are only 32 keywords in C whose strength lie in their rich built in functions.

Some of the keywords are:

									 auto	  double	int 		struct
									 break 	  else 		long		switch 
									 case 	  enum 		register 	typedef
									 char 	  extern 	float 		return 
									 union 	  const		short 		unsigned
									 continue for 		signed		void 
									 default  goto 		sizeof 		volatile
									 do 	  if 		static 		while