Operators and Expressions

1 Operators and Expressions

What is Operator?

Simple answer can be given using expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and + is called operator. C language supports following type of operators.

  • Arithmetic Operators
  • Logical (or Relational) Operators
  • Bitwise Operators
  • Assignment Operator
  •  Conditional operators (ternary operators)
  • Increment/decrement operators
  • Special operators

 

Types of operators

  1. Arithmetic Operators:

There are following arithmetic operators supported by C language:

Assume variable A holds 10 and variable B holds 20 then:

 

Operator

Description

Example

+

Adds two operands

A + B will give 30

-

Subtracts second operand from the first

A - B will give -10

*

Multiply both operands

A * B will give 200

/

Divide numerator by denumerator

B / A will give 2

%

Modulus Operator and remainder of after an integer division

B % A will give 0

++

Increment operator, increases integer value by one

A++ will give 11

--

Decrement operator, decreases integer value by one

A-- will give 9

  1. Logical (or Relational) Operators:

There are following logical operators supported by C language

Assume variable A holds 10 and variable B holds 20 then:

 

Operator

Description

Example

==

Checks if the value of two operands is equal or not, if yes then condition becomes true.

(A == B) is not true.

!=

Checks if the value of two operands is equal or not, if values are not equal then condition becomes true.

(A != B) is true.

Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.

(A > B) is not true.

Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.

(A < B) is true.

>=

Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.

(A >= B) is not true.

<=

Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.

(A <= B) is true.

&&

Called Logical AND operator. If both the operands are non zero then then condition becomes true.

(A && B) is true.

||

Called Logical OR Operator. If any of the two operands is non zero then then condition becomes true.

(A || B) is true.

!

Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

!(A && B) is false.

  1. Bitwise Operators:

Bitwise operator works on bits and perform bit by bit operation.

Assume if A = 60; and B = 13; Now in binary format they will be as follows:

A = 0011 1100

B = 0000 1101

-----------------

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A  = 1100 0011

There are following Bitwise operators supported by C language

Operator

Description

Example

&

Binary AND Operator copies a bit to the result if it exists in both operands.

(A & B) will give 12 which is 0000 1100

|

Binary OR Operator copies a bit if it exists in eather operand.

(A | B) will give 61 which is 0011 1101

^

Binary XOR Operator copies the bit if it is set in one operand but not both.

(A ^ B) will give 49 which is 0011 0001

~

Binary Ones Complement Operator is unary and has the efect of 'flipping' bits.

(~A ) will give -60 which is 1100 0011

<< 

Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.

A << 2 will give 240 which is 1111 0000

>> 

Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.

A >> 2 will give 15 which is 0000 1111

  1. Assignment Operators:

There are following assignment operators supported by C language:

 

Operator

Description

Example

=

Simple assignment operator, Assigns values from right side operands to left side operand

C = A + B will assigne value of A + B into C

+=

Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand

C += A is equivalent to C = C + A

-=

Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand

C -= A is equivalent to C = C - A

*=

Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand

C *= A is equivalent to C = C * A

/=

Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand

C /= A is equivalent to C = C / A

%=

Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand

C %= A is equivalent to C = C % A

<<=

Left shift AND assignment operator

C <<= 2 is same as C = C << 2

>>=

Right shift AND assignment operator

C >>= 2 is same as C = C >> 2

&=

Bitwise AND assignment operator

C &= 2 is same as C = C & 2

^=

bitwise exclusive OR and assignment operator

C ^= 2 is same as C = C ^ 2

|=

bitwise inclusive OR and assignment operator

C |= 2 is same as C = C | 2

5.  Conditional or ternary operators in C:

    • Conditional operators return one value if condition is true and returns another value is condition is false.
    • This operator is also called as ternary operator.

Syntax     :        (Condition? true_value: false_value);

Example :        (A > 100  ?  0  :  1);

.

    • In above example, if A is greater than 100, 0 is returned else 1 is returned. This is equal to if else conditional statements.

Example program for conditional/ternary operators in C:

C

1

2

3

4

5

6

7

8

#include <stdio.h>

int main()

{

        int x=1, y ;

        y = ( x ==1 ? 2 : 0 ) ;

        printf("x value is %d\n", x);

        printf("y value is %d", y);

}

Output:

x value is 1
y value is 2

6.  Increment/decrement Operators

  • Increment operators are used to increase the value of the variable by one and decrement operators are used to decrease the value of the variable by one in C programs.
  • Syntax:

Increment operator     :     ++var_name; (or) var_name++;
Decrement operator   :                                                         –  - var_name; (or) var_name –  -;

Example:

Increment operator :     ++ i ;    i ++ ;
Decrement operator:     – - i ;    i – - ;

Example program for increment operators in C:

In this program, value of “i” is incremented one by one from 1 up to 9 using “i++” operator and output is displayed as “1 2 3 4 5 6 7 8 9”.

C

1

2

3

4

5

6

7

8

9

10

11

12

//Example for increment operators

#include <stdio.h>

int main()

{

     int i=1;

     while(i<10)

     {

         printf("%d ",i);

         i++;

     }    

}

Output:

1 2 3 4 5 6 7 8 9

  1. Special operators

There are few other operators supported by C Language.

 

Operator

Description

Example

sizeof()

Returns the size of an variable.

sizeof(a), where a is interger, will return 4.

&

Returns the address of an variable.

&a; will give actaul address of the variable.

*

Pointer to a variable.

*a; will pointer to a variable.

Precedence of C Operators:

Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator:

For example x = 7 + 3 * 2; Here x is assigned 13, not 20 because operator * has higher precedenace than + so it first get multiplied with 3*2 and then adds into 7.

Here operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedenace operators will be evaluated first.

Category 

Operator 

Associativity 

Postfix 

() [] -> . ++ - -  

Left to right 

Unary 

+ - ! ~ ++ - - (type) * & sizeof 

Right to left 

Multiplicative  

* / % 

Left to right 

Additive  

+ - 

Left to right 

Shift  

<< >> 

Left to right 

Relational  

< <= > >= 

Left to right 

Equality  

== != 

Left to right 

Bitwise AND 

Left to right 

Bitwise XOR 

Left to right 

Bitwise OR 

Left to right 

Logical AND 

&& 

Left to right 

Logical OR 

|| 

Left to right 

Conditional 

?: 

Right to left 

Assignment 

= += -= *= /= %= >>= <<= &= ^= |= 

Right to left 

Comma 

Left to right