Using - C
 Source Code
#include<stdio.h>
#include<math.h>

int sumOfCube(int num);

void main() {
  int num;
  printf("Enter a number:  ");
  scanf("%d",&num);

  if(num == sumOfCube(num))
    printf("It is a Armstrong Number!");
  else
    printf("It is not a Armstrong Number!");
}

int sumOfCube(int num) {
int sum=0, cubeOfdigit, digit;
    while(num!=0) {
    digit = num % 10;
    cubeOfdigit = pow(digit,3);
    sum += cubeOfdigit;
    num /= 10;
    }
return sum;
}

Using - C++
 Source Code
#include<iostream>
#include<math.h>
using namespace std;

int sumOfCube(int n);

int main() {
int n, sum=0;
	cout<<"Enter a number: ";
	cin>> n;

	if(n == sumOfCube(n))
		cout<< "It is a Armstrong Number!";
	else
		cout<< "It is not a Armstrong Number!";

	return 0;
}

int sumOfCube(int n) {
int sum=0, cubeOfdigit, digit;
    while(n!=0) {
    digit = n % 10;
    cubeOfdigit = pow(digit,3);
    sum += cubeOfdigit;
    n /= 10;
    }
return sum;
}