C++ Factorial

the factorial of a positive integer number n! is the product of all integers less than or equal to n.
For example :

5! = 5x4x3x2x1.

here's a typical implementation of function using for,while and do-while loop.

i) for loop

#include<iostream>
using namespace std;

int main()
{
    int n;
    int fac = 1;

    cout << " Please enter an Integer : " ;
    cin >> n;
    cout << " The Factorial of " <<n<< "!= ";

    for (n>=0;n>0;n--)
    {
        fac = fac*n;
        cout<<n;
        if(n!=1)
        cout << " x ";
    }

    cout << " = " <<fac<<endl;
    system ("pause");
    return 0;
}


ii) while loop


#include <iostream>
using namespace std;

int main ()
{
  int n;
  int fac = 1;
  cout << "Please enter an integer : ";
  cin >> n;
  cout << "The factorial of " <<n<< "! = " ;

  while (n>0)
  {
    fac = fac * n;
    cout << n;

    if(n!=1)
    cout << " x "  ;
    --n;
  }

  cout << " = " << fac<< endl;
  system ("pause" );
  return 0;


iii) do-while loop


#include <iostream>
using namespace std;

int main()
{
    int n;
    int fac = 1;

    cout << " Please enter an integer : ";
    cin >>n;
    cout << " The Factorial of " <<n<< "! = ";
{
         do
         {
         
              fac = fac*n;
              cout <<n;
              if (n!=1)
              cout << " x ";
              n--;
              }
              while (n>0);
              }
              cout << " = " <<fac<<endl;
              system ("pause");
              return 0;
              }