Tokens in C

Tokens are classified as

• Keywords
• Identifiers
• Operators
• Constants
• Special Symbols

Keywords

Keywords are reserved by the compilers and keywords will not be redefined (means the keywords are not been declared as variable names, etc). There are standard 32 keywords in C compiler, and some compilers uses more keywords based on their specification. Here is the list of 32 keywords

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

 

Identifiers

1. Identifiers are variable names declared inside the program.
2. They use alphabets, number, symbols like _ and $
3. They must begin with  alphabet or _
4. They are case sensitive i.e Var_name is different from var_name

Some valid identifiers are

john	Value	r_sie	x1
x2	Chennai	Sum1	abcd

invalid identifiers

123	%	(super)	25th
1st	ab-d	sum of total

 

Operators

operators are further classified into different categories like

• Arithmetic operators

+  - for addition   1+3 = 4

-   for subtraction      3 – 2 = 1        

*  for multiplication 4* 2 = 8

/   for Division      4 / 2    = 2

% for modulo  4 % 3 = 1 (when 4 is divided by 3, the remainder is 1)

• Increment/ Decrement operators

++  increment Ex: a++ or ++a

--  decrement Ex: a—or –a

• relational Operators

< – less than

> – greater than

<= less than or equal to

>= greater than or equal to

== is equal to

• logical operators

&&  - Logical AND

||   - Logical OR

!  - Logical NOT

• bitwise operators

& Bitwise AND

| bitwise OR

^ bitwise XOR

~ one’s complement

<< shift left

>> shift right

• Conditional Operators

? : Conditional operator

f =(a>b) ?a : b;

if the condition a> b is true then

a is assigned to f and if false then b is assigned to f

the statement can be rewritten as

if(a>b>

{

f=a;

}

else

{

f=b;

}

• Other Operators

= assignment operator (this is not equality operator, it just assigns the value to some other variable from right to left assignment)

Example: a=b means b is assigned to a

, comma operator (This is to separate the array variables, etc)

sizeof() operator (to find out the various sizes of the entities like int, char, array size, etc)

• Special symbols

{} This to begin and end any statement, loop in C program

[] This is for specifying the array index (Ex: int a[10];)

()  This is used for functions in C and helpful for grouping arithmetical operations

Constants

• Constants is an entity will never changes it value during the execution of the program
• They are different from variables

 

• Integer constant

Examples are 2, –1, 0, 345, 324, etc

• float Constant

Examples are 3.0, –2.345, 32.56, 4.65

• String Constant

“abc”, “Pradeep Kumar”

• Character constant

‘A’, ‘b’, ‘1’

There are two ways to declare a constant

1st way is to define at the preprocessing level

Example is

#define PI 31.4

2nd way is declare inside the program

const int a=3.14;

const is the keyword to define a constant.