factorial (!) function (for n>=0):
f(0) := 1
f(n) := f(n-1)*n     [ for n > 0 ]

Write a program that solves this function recursively, and write a main function that
asks the user for a number and prints out the result

#include...
using...

int factorial(int n)
{
  if (n==0) 
  {
     return 1;
  }
  else 
  {
     return factorial(n-1)*n;
  }
}

int main()
{
  int num;
  cout << "Factorial of which number:"; cin >> num;
  cout << "That is: " << factorial(num) << endl;
  return 0;
}


5! = 4! * 5 = 3! * 4 * 5 = 2! * 3 * 4 * 5 = 1! * 2 * 3 * 4 * 5 = 0! * 1 *2 *3 *4*5=1*1*2*3*4*5