test.cpp

#include <iostream>

int Factorial(int number);

int main() {
   for(int i = 1; i < 10; i ++)
      std::cout << i <<"! is " << Factorial(i) << std::endl;

   return 0;
}

int Factorial(int number) {
   return (number == 1) ? number : (number * Factorial(number - 1));
}