TOKENS, C++

Tokens
A token is the smallest element of a C++ program that is meaningful to the compiler. The C++ recognizes the following tokens:

• Identifiers
• Keywords
• Literals / Constants
• Operators
• String

Tokens are usually separated by white space. White space can be one or more blanks, Horizontal or Vertical tab, New lines, Form feeds, Comments. 

Identifiers

An identifier is a sequence of characters. Which are used to denote object or variable name, class, structure, or union name, functions name etc. Doesn't use the keywords as a Identifiers, it will get error.

Keywords

Keywords are predefined reserved identifiers that have special meanings. They cannot be used as identifiers in the program. C++ reserved Keywords are listed following.

asm	default	goto	register	throw
auto	delete	if	return	try
bool	do	inline	short	typedef
break	double	int	signed	union
case	else	long	sizeof	unisigned
catch	enum	new	static	virtual
char	extern	operator	struct	void
class	float	private	switch	volatile
const	for	protected	template	while
continue	friend	public	this

Literals / Constant

Invariant program elements are called "Literals" or Constants". Constants means the program may not alter the fixed value and they called literal. The terms 'Literal' and ' constant' are used interchangeably here. Literals fall into four major categories. They are integer, character, floating point and string literals.

Character Constant: The character type is used to store characters. 'char' keyword is used to declare these types of variable. Range of character type is -128 to 127 and size is one byte.

Integer Constant: The integer type is used for storing whole numbers without fraction parts. We can use signed, unsigned or plain integer values. Integer values come in three sizes, plain int, short int, long int. The range of values of these types will be defined by compiler. Normal range is -32768 to 32767. Size is 2 bytes.

Floating Constant: Floating constants contain decimal numbers. They are also called Real Constant. It consist of signed or unsigned digits including a decimal points, for example 1.16, - .085.

Operator
Operator are special symbols used for specific purpose. C++ provides six types of Operators.

• Arithmetic Operator
• Relational Operator
• Logical Operator
• Unary Operator
• Assignment Operator
• Conditional Operator
• Comma Operator

String
String is represented by a group of characters. String constant are enclosed in double quotes.