Keywords, Tokens, Identifier in C

Keywords are pre – defined (already defined) words in a C compiler. Every keyword is meant to perform a specific function i.e. There are 32 keywords in c ( i.e.  while, do, switch, else, if  for,  go to, default, auto, break, continue, const, char, case, float, void etc) Keywords cannot be used as variable name. The most important keywords are

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

Identifier : –

Identifier refer to name of variable, functions and array these are defined by user but they cannot have letters and digits, with a letter as a first character. Both uppercase and lowercase letters are permitted but lower case letters are commonly used.

Rules of identifier:-

First character must be an alphabet.
Only first 31 characters are significant.
Cannot use a keyword.

C tokens: –

In a passage of text Individual words and punctuation marks are called tokens. Similarly in C program the smallest individual units are known as C Tokens.

There are six types of C tokens.

Keywords(eg: int, while)
Identifiers(eg: main, total)
Constants(eg: 15, 4)
Strings(eg: “safal”, “hi”)
Special symbols(eg: (), {}, [])
Operators(eg: +,-,*, /,%)
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