Tokens in C

Tokens : In C programs, each word and punctuation is referred to as a token. 

C Tokens are the smallest building block or smallest unit of a C program.

C Supports Six Types of Tokens:

1. Keywords
2. Identifiers
3. Constants
4. Strings
5. Operators
6. Special characters

Keywords : A keyword is a reserved word. You cannot use it as a variable name, constant name etc.

There are only 32 reserved words (keywords) in the C language.

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

Identifiers : An identifier is a name that is assigned by the user for a program element such as variable, type, template, class,function or namespace. 

It is usually limited to letters, digits, and underscores.

Identifiers are used to identify a program element in the code.

Rules for Naming Identifiers :

1.  An identifier can only have alphanumeric characters (a-z, A-Z, 0-9) (i.e. letters & digits) and underscore( _ ) symbol.
2. Identifier names must be unique.
3. The first character must be an alphabet or underscore.
4. You cannot use a keyword as identifiers.
5. Only first thirty-one (31) characters are significant.
6. Must not contain white spaces.
7. Identifiers are case-sensitive.

Constants : Constants are like a variable, except that their value never changes during execution once defined.

C Constants is the most fundamental and essential part of the C programming language. 

Constants in C are the fixed values that are used in a program, and its value remains the same during the entire execution of the program.

Constants are also called literals and can be any of the data types.

const keyword defines a constant in C.

Strings : A string is a sequence of characters terminated with a null character "\0"

For example: char c[  ] = "c string";

c

s

t

r

i

n

g

\0

When the compiler encounters a sequence of characters enclosed in the double quotation marks, it appends a null character "\0" at the end by default.

Operators : An operator is a symbol that operates on a value or a variable. 

For example: "+" is an operator to perform addition.C has a wide range of operators to perform various operations.

C programming language offers various types of operators having different functioning capabilities.

1. Arithmetic Operators
2. Relational Operators
3. Logical Operators
4. Assignment Operators
5. Increment and Decrement Operators
6. Conditional Operator
7. Bitwise Operators
8. Special Operators

Arithmetic Operators : Arithmetic Operators are used to performing mathematical calculations like addition (+), subtraction (-), multiplication (*), division (/) and modulus (%).

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus

Increment and Decrement Operators : Increment operator ++ increases the value by 1 whereas decrement operator -- decreases the value by 1.

Operator	Description
++	Increment
−−	Decrement

Relational Operators : Relational operators are used to comparing two quantities or values.

Operator	Description
==	Is equal to
!=	Is not equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to

Logical Operators : C provides three logical operators when we test more than one condition to make decisions. 

These are: && (meaning logical AND), || (meaning logical OR) and ! (meaning logical NOT).

Operator	Description
&&	And operator. It performs logical conjunction of two expressions. (if both expressions evaluate to True, result is True. If either expression evaluates to False, the result is False).
||	Or operator. It performs a logical disjunction on two expressions. (if either or both expressions evaluate to True, the result is True).
!	Not operator. It performs logical negation on an expression.

Bitwise Operators : C provides a special operator for bit operation between two variables.

Operator	Description
<<	Binary Left Shift Operator
>>	Binary Right Shift Operator
~	Binary Ones Complement Operator
&	Binary AND Operator
^	Binary XOR Operator
|	Binary OR Operator

Assignment Operators : Assignment operators applied to assign the result of an expression to a variable. 

C has a collection of shorthand assignment operators.

Operator	Description
=	Assign
+=	Increments then assign
-=	Decrements then assign
*=	Multiplies then assign
/=	Divides then assign
%=	Modulus then assign
<<=	Left shift and assign
>>=	Right shift and assign
&=	Bitwise AND assign
^=	Bitwise exclusive OR and assign
|=	Bitwise inclusive OR and assign

Conditional Operator :  C offers a ternary operator which is the conditional operator (?: in combination) to construct conditional expressions.

Operator	Description
? :	Conditional Expression

Special Operators : C supports some special operators

Operator	Description
sizeof()	Returns the size of a memory location.
&	Returns the address of a memory location.
*	Pointer to a variable.

Special Characters : There are some Special Characters in C Programming, which are as shown in the table.

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