Bitwise Operators in C

Bitwise Operators

            

C language supports bitwise operators as &, |, ^, ~, << and >> operators.  These operators are used to manipulate data of the operands at bit level i.e., operations are performed on corresponding bits of the given operands.

Bitwise operators can operate only on integer quantities such as int, char, short int, long int etc.,

Bit-Wise AND, Bit-Wise OR and Bit-Wise Exclusive OR follows the following bit comparison tables.

Bit1	Bit2	Bit1 & Bit2	Bit1 | Bit2	Bit1 ^ Bit2
0	0	0	0	0
0	1	0	1	1
1	0	0	1	1
1	1	1	1	0

Here,

Ø  Bit-Wise AND compares the corresponding bits of the operands and produces 1 when both bits are 1; 0 otherwise.

Ø  Bit-Wise OR compares the corresponding bits of the operands and produces 0 when both bits are 0; 1 otherwise.

Ø  Bit-Wise Exclusive OR compares the corresponding bits of the operands and produces 0 when both bits are same; 1 otherwise.

For the above operations consider the following number conversion system for octal and hexa-decimal numbers.

NUMBER	OCTAL	HEXADECIMAL
0	000	0000
1	001	0001
2	010	0010
3	011	0011
4	100	0100
5	101	0101
6	110	0110
7	111	0111
8		1000
9		1001
A - 10		1010
B – 11		1011
C – 12		1100
D – 13		1101
E – 14		1110
F - 15		1111

Example:

           

1.         X         : 011                0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1

            Y         : 027                0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 1             (Octal)

X&Y   :                       0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1             : 1

X|Y     :                       0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1             : 37

            X^Y    :                       0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0             : 36

2.         X         : 0X7B                        0 0 0 0 0 0 0 0 0 1 1 1 1 0 1 1

            Y         : 0X129           0 0 0 0 0 0 0 1 0 0 1 0 1 0 0 1     (Hexadecimal)

            X&Y   :                       0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1             : 29

            X|Y     :                       0 0 0 0 0 0 0 1 0 1 1 1 1 0 1 1             : 17B

            X^Y    :                       0 0 0 0 0 0 0 1 0 1 0 1 0 0 1 0             : 152

One’s Complement (or) Bit Negation operator is a unary operator that complements the bits of the given operand. i.e., Bit 0 converted into Bit 1 and Bit 1 converted into Bit 0.

Example:

X         : 0X7B                        0 0 0 0 0 0 0 0 0 1 1 1 1 0 1 1

~X       :                       1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0             :           FF84

Shift Operators:                    Left shift operator (<<) and right shift operator (>>) are known as shift operators.  They perform left and right shifts of their operand bits by the number of bit positions specified by the argument which must be integer and positive number.

Left Shift Operator Syntax:

            VariableName << NoOfBitPositions;

Example:        Let X = 36

                        X << 2;

Ø  While performing left shift operations, there is a loss of data at MSB side.

Ø  The vacated positions at LSB side are filled with zeros.

Ø  For each shift value by the number of bits, the result value is equivalent to multiplication by 2.

Right Shift Operator Syntax:

            VariableName >> NoOfBitPositions;

Example:        Let X = 36

                        X >> 2;                          

Ø  While performing right shift operations, there is a loss of data at LSB side.

Ø  The vacated positions at MSB side are filled with zeros.

Ø  For each shift value by the number of bits, the result value is equivalent to division by 2.

/* EXAMPLE PROGRAM FOR SHIFT OPERATORS */

#include<stdio.h>

#include<conio.h>

main()

{

            int x;

            clrscr();

            x=36;

            printf("\nLeft Shift Result:%d",x<<2);

            x=36;

            printf("\nRight Shift Result:%d",x>>2);

}