C Programming Code Examples C > Bitwise Operators Code Examples C program to get lowest order or first set bit of a number C program to get lowest order or first set bit of a number Write a C program to input any number from user and find lowest order set bit of given number using bitwise operator. How to find first set bit in a given number using bitwise operator in C programming. Lowest order or first set bit of any number is the first bit set starting from left to right. Lowest order set bit of any odd number is 0 since first bit of any odd number is always set. Logic to get lowest order set bit is almost similar to highest order set bit of a number. 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. Run a loop from 0 to INT_SIZE. The loop structure should look like for(i=0; i<INT_SIZE; i++). Initialize a variable to store lowest order set bit, say order = 0;. Inside the loop if ith bit is set then update order to i i.e. order = i; and terminate from loop. #include <stdio.h> #define INT_SIZE sizeof(int) * 8 /* Integer size in bits */ int main() { int j, order, i; /* Input number from user */ printf("Enter any number: "); scanf("%d", &j); /* Initially set the order to max size of integer */ order = INT_SIZE - 1; /* Iterate through each bit of integer */ for(i=0; i<INT_SIZE; i++) { /* If current bit is set */ if((j>>i) & 1) { order = i; /* Terminate the loop */ break; } } printf("Lowest order set bit in %d is %d", j, order); return 0; }