Keywords and Identifiers

Keywords and Identifiers

 

In this tutorial, you will learn about Tokens (keywords, identifiers,

Strings, Operators), Character set, etc.

Character Set:-

C has the rich set of character that are Litters (A-Z), Digits (0-9), special character ({}, [], , .,etc).

Letters

Uppercase: A  B  C-------------------X  Y  Z

Lowercase: a  b  c--------------------x  y  z

Digits

1  2  3  4  5  6  7  8  9  0

Special Characters

+	<	>	.	-
)	(	;	&	:
%	}	{	#	?
‘	$	[	]	“
^	!	*	\	|
_	/	~	,

White space Characters

New line, Horizontal tab, Carriage returns and black space.

Tokens:-

As we know the smallest individual units in a program are known as tokens.

C has the following tokens:-

• Keywords
• Identifiers
• Constants
• Strings
• Operators
  
  

A C program writing using these tokens, white spaces and the syntax of the language .

KeyWord:

                      They are reserved identifier and cannot be used as variable names. The keywords in C are:-

                                       Keywords of C

auto	double	int	struct
Do	if	static	while
Default	goto	sizeof	volatile
Continue	for	signed	void
Const	float	short	unsigned
Char	extern	return	union
Case	enum	register	typedef
Break	else	long	switch

There are several numerous keywords depending upon the compiler.

Example:- int ashu; Here, int is a keyword that indicates ‘ashu’ is a variable of type integer.

Identifiers:-

                         Identifiers refer to the name of variables, function, array, and structures etc, created by the user. They are fundamental requirement of any language. Each language has its own rule to identifiers. Some rules in C are given below:-

1.              A valid identifier is a series of one or more letters, digits or underscores characters.
2. Neither spaces nor punctuation marks or symbols can be part of an identifier.
3. Only letters, digits and single underscore characters are valid.
4. Variable identifiers always have to begin with a letter.
5. They can also begin with an underline with letter.

Important:               The C language is a case sensitive language. It means let we have two identifiers which have same name but one is written in capital letters and another in small is not equivalent. Thus, for example, the HAPPY variable is not the same as the happy variable or the Result variable.