C program to get highest order set bit of a number

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C program to get highest order set bit of a number

Write a C program to input any number from user and find highest order set bit of given number using bitwise operator. How to find the highest order of the set bit of a given number using bitwise operator in C programming. Logic to get highest order set bit of a number in C programming.

Required knowledge

Operators, Data Types in c, Variables in C, Basic input/output, C if-else, C Loops

Highest order set bit

Highest position of a set bit from left to right in a number is said to be highest order set bit of that number. Highest order set bit of any negative integers is 31 (for 32 bit signed integer). Since, highest order set bit of any negative number is its Most Significant Bit (MSB).

Logic to get highest order set bit of a number

Step by step descriptive logic to get highest order set bit of a number.

1. Input number from user. Store it in some variable say, num.

2. Find total bits required to store an integer in memory say, INT_SIZE = sizeof(int) * 8.

3. Read more - How to find size of a data type using sizeof() operator.

4. Run a loop from 0 to INT_SIZE. The loop structure should look like for(i=0; i<INT_SIZE; i++).

5. Initialize a variable to store highest order, say order = -1;.

6. Inside the loop if ith bit is set then update order to i i.e. order = i;.

Program to get highest order set bit of a number

/**
 * C program to find highest order set bit in a number
 */

#include <stdio.h>
#define INT_SIZE sizeof(int) * 8 /* Integer size in bits */

int main()
{
    int num, order = -1, i;

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

    /* Iterate over each bit of integer */
    for(i=0; i<INT_SIZE; i++)
    {
        /* If current bit is set */
        if((num>>i) & 1)
            order = i;
    }

    if (order != -1)
        printf("Highest order set bit in %d is %d", num, order);
    else 
        printf("0 has no set bits.");

    return 0;
}

Output:

Enter any number: 22
Highest order set bit in 22 is 4

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