Example: C Program to Check Armstrong Number using Function

// C Program to Check Armstrong Number using Function
#include <stdio.h>
#include <math.h>

// This function will check input number is armstrong or not
void CheckArmstrong(int x) {
    int y, rem, n = 0;
    float r = 0.0;

    // y - To store the storage of original input number to check
    // rem - To store the reminder
    // r - To store the result variable

    y = x;

    // store the number of digits of x in n
    for (y = x; y != 0; ++n) {
        y /= 10;
    }

    for (y = x; y != 0; y /= 10) {
        rem = y % 10;
        // store the sum of the power of individual digits in r
        r += pow(rem, n);
    }

    // if x is equal to r, the number is an Armstrong number
    if ((int) r == x) {
        printf("%d is an Armstrong number.\n", x);
    } else {
        printf("%d is not an Armstrong number.\n", x);
    }
}

// It's the driver function
int main() {
    int x; // To store the input number

    printf("-----Enter the integer number-----\n");
    scanf("%d", &x);

    CheckArmstrong(x);
    return 0;
}