C program to count zeros and ones in a binary number

Write a C program to input a number from user and count total number of ones (1s) and zeros (0s) in the given number using bitwise operator. How to count zeros and ones in a binary number using bitwise operator in C programming.



Input any number: 22


Output number of ones: 3
Output number of zeros: 29

Required knowledge

Bitwise operators, Data types, Variables and Expressions, Basic input/output, If else, For loop

Logic to count zeros and ones in a binary number

Step by step descriptive logic to count zeros and ones in a binary number.

  1. Input a number from user. Store it in some variable say num.
  2. Compute total bits required to store integer in memory i.e. INT_SIZE = sizeof(int) * 8.

    Must read - How to find size of a data type using sizeof() operator.

  3. Initialize two variables to store zeros and ones count, say zeros = 0 and ones = 0.
  4. Run a loop from 0 to INT_SIZE. The loop structure should look like for(i=0; i<INT_SIZE; i++).
  5. Inside the loop check if Least Significant Bit of a number is set, then increment ones by 1 otherwise increment zeros by 1.
  6. Right shift num 1 time i.e. perform num = num >> 1;.

Program to count zeros and ones in a binary number

 * C program to count total of zeros and ones in a binary number using bitwise operator

#include <stdio.h>
#define INT_SIZE sizeof(int) * 8 /* Total number of bits in integer */

int main()
    int num, zeros, ones, i;

    /* Input number from user */
    printf("Enter any number: ");
    scanf("%d", &num);

    zeros = 0;
    ones = 0;

    for(i=0; i<INT_SIZE; i++)
        /* If LSB is set then increment ones otherwise zeros */
        if(num & 1)

        /* Right shift bits of num to one position */
        num >>= 1;

    printf("Total zero bit is %d\n", zeros);
    printf("Total one bit is %d", ones);

    return 0;

In the above code if(num & 1) is equivalent to if((num & 1) == 1).
In the statement num >>= 1; I have used shorthand assignment operator which is equivalent to num = num >> 1;


Enter any number: 22
Total zero bit is 29
Total one bit is 3

Happy coding 😉

About Pankaj

Pankaj Prakash is the founder, editor and blogger at Codeforwin. He loves to learn new techs and write programming articles especially for beginners. He works at Vasudhaika Software Sols. as a Software Design Engineer and manages Codeforwin. In short Pankaj is Web developer, Blogger, Learner, Tech and Music lover.

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