This program prints all Armstrong numbers between 1 and 100 in the C programming language.

## Problem Statement

Given a range of natural numbers from 1 to 100, write a C program to find and print all Armstrong numbers in this range.

## Solution

To solve this problem, we will write a function called `isArmstrong()`

that takes an integer argument `num`

and returns a boolean value indicating whether or not `num`

is an Armstrong number. We will then use a loop to iterate over all numbers from 1 to 100 and print those that are Armstrong numbers. Here’s the code:

#include <stdio.h> #include <stdbool.h> bool isArmstrong(int num); int main() { int i; printf("Armstrong numbers between 1 and 100 are:\n"); for (i = 1; i <= 100; i++) { if (isArmstrong(i)) { printf("%d\n", i); } } return 0; } bool isArmstrong(int num) { int temp, digit, sum = 0; temp = num; while (temp != 0) { digit = temp % 10; sum += digit * digit * digit; temp /= 10; } return num == sum; }

## Output

Let’s go through the code step-by-step:

- We include the standard input/output header file
`stdio.h`

and the boolean header file`stdbool.h`

. - We declare a function called
`isArmstrong()`

that takes an integer argument`num`

and returns a boolean value. This function will be used to check if a number is an Armstrong number or not. - In the
`main()`

function, we declare an integer variable`i`

and use a loop to iterate over all numbers from 1 to 100. For each number, we call the`isArmstrong()`

function to check if it is an Armstrong number. If it is, we print it using the`printf()`

function. - The
`isArmstrong()`

function is defined below the`main()`

function. It takes a single integer argument`num`

, which is the number to be checked for Armstrong property. - Inside the
`isArmstrong()`

function, we declare three integer variables`temp`

,`digit`

, and`sum`

. We initialize`temp`

to`num`

, which will be used to extract each digit of`num`

. We initialize`sum`

to 0, which will be used to store the sum of cubes of digits of`num`

. - We then use a while loop to extract each digit of
`num`

and add its cube to`sum`

. We divide`temp`

by 10 to remove the last digit of`num`

. This process continues until`temp`

becomes 0. - Finally, we check if
`num`

is equal to`sum`

. If it is, we return`true`

(indicating that`num`

is an Armstrong number), otherwise we return`false`

.

## Explanation

An Armstrong number is a number that is equal to the sum of cubes of its digits. For example, 153 is an Armstrong number because 1^3 + 5^3 + 3^3 = 153. To check if a number is an Armstrong number, we need to extract each digit of the number, cube it, and add the cubes. If the result is equal to the original number, then the number is an Armstrong number.

The `isArmstrong()`

function takes an integer argument `num`

and extracts each digit of `num`

using a while loop. Inside the loop, we extract the last digit of `num`

using the modulus operator `%`

and store it in the variable `digit`

. We then cube `digit`

and add it to `sum`

. We remove the last digit of `num`

by dividing `temp`

by 10, and the loop continues until `temp`

becomes 0. Once the loop is finished, we check if `num`

is equal to `sum`

. If it is, we return `true`

, indicating that `num`

is an Armstrong number. If it isn’t, we return `false`

.

In the `main()`

function, we use a loop to iterate over all numbers from 1 to 100. For each number, we call the `isArmstrong()`

function to check if it is an Armstrong number. If it is, we print it using the `printf()`

function.

## Conclusion

In this program, we used a loop and a function to find all Armstrong numbers between 1 and 100 in the C programming language. Armstrong numbers are numbers that are equal to the sum of cubes of their digits. By extracting each digit of a number, cubing it, and adding the cubes, we can check if a number is an Armstrong number. The `isArmstrong()`

function uses this process to check if a number is an Armstrong number, and the `main()`

function uses a loop to find and print all Armstrong numbers between 1 and 100.