• Source 
    1. //Calculador de factorial
    2. #include <iostream>
    3. using namespace std;
    4.  
    5. long factorial(long a)
    6. {
    7. 	if (a > 1)
    8. 	return (a * factorial (a-1));
    9. 	else
    10. 	return 1;
    11. }
    12.   int main ()
    13.   {
    14.   	long numero = 9;
    15.   	cout << numero << "! = " << factorial(numero); 
    16.   }