Bitwise Operators in C

Bit level operators make C useful for many low level applications. Bitwise operations allow one to read and manipulate bits in variables of certain types. The bit wise operators only work on int and char types.

The following are the bitwise operators in C

Operator	Description
~	Bitwise Complement
<<	Bitwise Shift Left
>>	Bitwise Shift Right
&	Bitwise AND
^	Bitwise EX-OR
|	Bitwise OR

Bitwise operations helps to work on Boolean variable, which needs only one bit.Set membership can be represented with Boolean variables ( 1 means element in the set 0 means not in the set) and the Bitwise-AND can be used to implement set-intersection and Bitwise-OR to implement set union.

The bitwise AND(&) is true only if both bits are set. The bitwise OR(|) is false only when both the bits are false. The bitwise EX-OR operation returns 1 if the input bits are different.

The following chart defines these bitwise binary operations

Variable	Decimal Equivalent	B3	B2	B1	B0
x	12	1	1	0	0
y	10	1	0	1	0
x&y	8	1	0	0	0
x|y	14	1	1	1	0
x^y	6	0	1	1	0

Bitwise NOT operation is the unary operator which flips the bits. It is also known as 1’s complement operator. This changes each 1 to 0 and 0 to 1.

Variable	Decimal Equivalent	B3	B2	B1	B0
x	12	1	1	0	0
~x	3	0	0	1	1

Bitwise SHIFT operators << and >> perform left and right shifts of their left operand by the number of bit positions given by the right operand, which must be non negative.

 
When we shift left , the most significant bits are lost and the vacated least significant bits are zero. Similarly when we shift right least significant bits are lost and the most significant bits become zero.

 
Eg:
int x=5 // 0000 0000 0000 0101
y=x<<2; // x is shifted left two times and the result is stored in y.
so y become 20 //0000 0000 0001 0100
z=x>>2;// x is shifted right two times and the result is stored in z
so z become 1 // 0000 0000 0000 0001

 

Many programs can be written efficiently using bit wise operator, which otherwise require loops ,division etc..

Examples

1. Check whether the given number is even or odd

#include <stdio.h>
void main()
{
int n;
printf("enter the number..\n");
scanf("%i",&n);
if(n & 0x00000001)
printf("odd\n");
else
printf("even\n");
}
2.Check whether the given number is a power of 2.
#include <stdio.h>
int main()
{
int n;
printf("Enter the number..\n");
scanf("%d",&n);
if(n & (n-1)==0)
  printf("The number is Power of 2\n");
else
  printf("The number is not power of 2\n");
return 0;
}
3.Exchanging the values of two variables with out using a temporary variable
#include <stdio.h>
int main()
{
int a,b;
printf("Enter the a and b..\n");
scanf("%d %d",&a,&b);
a=a^b;
b=b^a;
a=a^b;
printf("The swapped values of a and b\n",a,b);
return 0;
}
4.16 bit Binary equivalent of an integer number
#include <stdio.h>
void main()
{
unsigned short int n,i;
unsigned short int mask=0x8000;
int t;
printf("enter the number..\n");
scanf("%hu",&n);
for(i=0;i<16;i++)
{
 t=n&mask;
 putchar(t==0?'0':'1');
 n=n<<1;
}
printf("\n");
}

5.printing the binary and also counting the number of 1's 

#include <stdio.h>
void main()
{
unsigned short int n;
int count=0;
unsigned short int mask=0x8000;
printf("enter the number..\n");
scanf("%hu",&n);
while(mask!=0)
{
if(n & mask)
   {printf("1");count++;}
else
    printf("0");
mask=mask>>1;
}
printf("\nNumber of ones=%d\n",count); 

}

6.Write an easy to read C program to process a set of n natural numbers and to find the largest even number and smallest odd number from the given set of numbers. The program should not use division and modulus operators.

#include <stdio.h>
void main()
{
int n,i,x,le=-1,so=9999;
printf("enter n..\n");
scanf("%i",&n);
printf("enter %d numbers\n",n);
for(i=0;i<n;i++)
{
scanf("%d",&x);
if(x & 0x00000001)
   {if(x<so) so=x;}
else
   {if(x>le) le=x;}
}
printf("Largest even=%d smallest odd=%d\n",le,so);
}

7. Write a C program using bitwise operators to count the number of 1’s in the binary representation of the given number ( University Question)

#include <stdio.h>

int countOnes(int num) {

int count = 0;

while (num != 0) {

// Check the least significant bit

if (num & 1) {

count++;

}

// Right shift the number by 1

num >>= 1;

}

return count;

}

void main() {

    int number;

printf("Enter an integer: ");

scanf("%d", &number);

int result = countOnes(number);

printf("The number of 1s in the binary representation of %d is: %d\n",

number, result);

}