**Introduction**

An Armstrong number (also known as a narcissistic number, pluperfect digit, pluperfect number, or pluperfect digital invariant) in a given number base is a number that is the sum of its own digits raised to the power of the number of digits. C, a classic and foundational programming language, provides a straightforward approach to identifying such numbers. In this article, we will explore how to determine if a number is an Armstrong number using the C programming language.

**What is an Armstrong Number?**

An **Armstrong number** of a given number of digits is an integer such that the sum of its own digits raised to the power of the number of digits is equal to the number itself.

**For example:**

- 153 is an Armstrong number because: 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153

**C Implementation**

**Algorithm**:

- Take a number as input.
- Calculate the number of digits in the number.
- For each digit, raise it to the power of the total number of digits and calculate the sum.
- Compare the calculated sum with the original number. If they are the same, it’s an Armstrong number.

**Code Example**:

```
#include <stdio.h>
#include <math.h>
int main() {
int num, temp, sum = 0, n = 0;
printf("Enter a number: ");
scanf("%d", &num);
temp = num;
// Calculate number of digits
while(temp != 0) {
temp /= 10;
++n;
}
temp = num;
// Calculate sum of nth power of each digit
while(temp != 0) {
sum += pow(temp % 10, n);
temp /= 10;
}
if(sum == num)
printf("%d is an Armstrong number\n", num);
else
printf("%d is not an Armstrong number\n", num);
return 0;
}
```

Here, two libraries are included:

`stdio.h`

: This is the standard input-output library in C. It provides functions to read and write data. In our code, it is used for printing to the console and reading user input.`math.h`

: This library provides mathematical functions. In our code, it is used for the`pow()`

function which calculates the power of a number.

`num`

– Stores the number input by the user.`temp`

– Temporary variable used to manipulate and check the value of`num`

without altering it.`sum`

– Stores the sum of the nth power of each digit of the number.`n`

– Counts the number of digits in the number.

This loop runs until `temp`

becomes 0. In each iteration, `temp`

is divided by 10 (which effectively removes its last digit), and the count `n`

is incremented. This gives us the total number of digits in the number.

Here, we reset the value of `temp`

to `num`

to go through its digits again. For each digit (retrieved using `temp % 10`

), we raise it to the power of `n`

using `pow()`

and add it to the `sum`

. Then, we remove the last digit of `temp`

by dividing it by 10. This loop continues until all digits of `temp`

are processed.

We compare the `sum`

to the original `num`

. If they are equal, the number is an Armstrong number. Otherwise, it’s not The `return 0;`

statement signifies successful termination of the program.

**Conclusion**

Armstrong numbers are a fascinating mathematical concept, and their implementation in C helps novice programmers understand loops, conditional statements, and arithmetic operations in a real-world context. By working on such foundational concepts, one can grasp the intricacies of programming languages like C and cultivate logical thinking and problem-solving skills.