Keywords

C has a set of reserved keywords. They have a basic meaning behind them. They are written in lower case. In all there are 32 keywords.

Following table provides with all the keywords:

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

Identifiers

Identifiers are the names given to the variables, constants, functions and the user-defined data.
Identifiers are written by keeping in mind a set of rules.

The rules are as follows:

1. Special characters or punctuation marks like #, $, ^,?, . etc cannot be included. But an '_' underscore can be used.
2. Two successive underscores cannot be used at the same time.
3. Any keywords cannot be used as an identifier.
4. Identifiers are case-sensitive.
5. The identifier name can begin with an alphabet or an underscore.
6. An identifier can be of any reasonable length, but it should not contain more than 31 characters.