Tokens in C++ Programming

Tokens

• A token is a group of characters.
• It is the smallest element of a C++ program which is meaningful to the compiler.

C++ uses the following types of Tokens:
1. Keywords
2. Identifiers
3. Data types
4. Operators

1. Keywords

• Keywords are the reserved identifiers that have special meanings.
• These reserved keywords cannot be used as identifiers in a program.
• All keywords are written in lower case.

Following are the keywords used in C++:

asm	default	float	operator	static_cast	union
auto	delete	for	private	struct	unsigned
break	do	friend	protected	switch	using
bool	double	goto	public	template	virtual
case	dynamic	if	register	this	void
catch	else	inline	reinterpret_cast	throw	volatile
char	enum	int	return	true	wchar_t
class	explicit	long	short	try	while
const	extern	Mutable	signed	typedef
const_cast	export	namespace	sizeof	typeid
continue	false	new	static	typename

2. Identifiers

Identifier is a sequence of characters used to define various things like variables, constants, functions, classes, objects, structures, unions etc.

It follows the rules for the formation of an identifier:

• An identifier consists of alphabets, digits or underscores.
• It cannot start with a digit. It can start either with an alphabet or underscore.
• Identifier should not be a reserved word.
• C++ is case-sensitive. So, upper case and lower case letters are considered different identifiers from each other.
• Blank spaces and special symbols are not allowed except underscore.

3. Data types

• Data type is used for identifying the type of data and the memory locations are required for storing the type of data in the memory.
• Whenever a variable is declared it becomes necessary to define data type.

Following are the C++ data types:

Data type	Range	Bytes
char	-127 to 128	1
signed char	-127 to 128	1
unsigned char	0 to 255	1
int	-32768 to 32767	2
signed int	-32768 to 32767	2
unsigned int	0 to 65535	2
short int	-32768 to 32767	2
long int	-2147483648 to 2147483647	4
signed short int	-32768 to 32767	2
signed long int	-2147483648 to 2147483647	4
unsigned short int	0 to 65535	2
unsigned long int	0 to 4294967296	4
float	3.4e-38 to 3.4e38	4
double	1.7e-308 to 1.7e308	8
long double	3.4e-4932 to 1.1e4932	10

4. Operators

• Operator is a symbol used to perform mathematical or logical manipulations.
• It specifies the order of operations in expressions that contain more than one operator.

It includes all C operators and has several new operators, as follows:

Operator	Description
Scope Resolution Operator (::)	It is used to identify and disambiguate identifiers used in different scopes.
Unary Operator ( - )	It returns the negative value of the variable to which it precedes.
Casting Operator ( () )	It is used for type conversion.
Address of Operator ( & )	It returns the address of a memory location.
sizeof() Operator	It returns the size of a memory location.
Comma ( , ) Operator	It allows grouping two statements where one is expected.
Indirection Operator or Value of Operator ( * )	It defines pointer to a variable.
Ternary Operator ( ?: )	It is a conditional expression.
New	Creates an instance of an object type.
Delete	Deletes property of an object.

Arithmetic Operators

Operator	Description
+	Addition
–	Subtraction
*	Multiplication
/	Division
%	Modulus (Reminder)
++	Increment
––	Decrement

Comparison Operators

Operator	Description
= =	Equal To
!=	Not Equal To
<	Less Than
>	Greater Than
<=	Less Than or Equal To
>=	Greater Than or Equal To

Assignment Operators

Operator	Description
=	Simple Assignment
+=	Add and Assignment
-=	Subtract and Assignment
*=	Multiply and Assignment
/=	Divide and Assignment
%=	Modulus and Assignment

Logical Operators

Operator	Description
&&	Logical AND
||	Logical OR
!	Logical NOT

Bitwise Operators

Operator	Description
&	Bitwise AND
|	Bitwise OR
^	Bitwise XOR
~	Bitwise NOT
<<	Left Shift
>>	Right Shift

Scope Resolution Operator

• Scope Resolution Operator is denoted by :: symbol.
• It is used to define a function outside a class.
• When Local variable and global variable having same name then local variable gets the priority.
• C++ allows flexibility of accessing both the variables through a scope resolution operator.