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C program to count leading zeros in a binary number



C program to count leading zeros in a binary number

Write a C program to input any number from user and find total number of leading zeros of the given number. How to find total leading zeros of a given number (in binary representation) using bitwise operator in C programming.

    Input number from user. Store it in some variable say, j.
    Find total bits required to store an integer in memory say, INT_SIZE = sizeof(int) * 8.
    Initialize a variable and set its MSB to 1, say msb = 1 << (INT_SIZE - 1);.
    Initialize a variable to store leading zeros count, say count = 0;.
    Run a loop from 0 to INT_SIZE. The loop structure should look like for(i=0; i<INT_SIZE; i++).
    Inside the loop, left shift j, i times and check its MSB is set or not. If its MSB is set i.e. if((j << i) & msb) then terminate the loop; otherwise increment count by 1.

/* C program to count leading zeros in a binary number using bitwise operator */

#include <stdio.h>
#define INT_SIZE sizeof(int) * 8

int main()
{
    int j, count, msb, i;

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

    // Equivalent to
    // 10000000 00000000 00000000 00000000
    msb = 1 << (INT_SIZE - 1);

    count = 0;

    /* Iterate over each bit */
    for(i=0; i<INT_SIZE; i++)
    {
        /* If leading set bit is found */
        if((j << i) & msb)
        {
            /* Terminate the loop */
            break;
        }

        count++;
    }

    printf("Total number of leading zeros in %d is %d", j, count);

    return 0;
}