Virtual function

#include <iostream>
#include <conio.h>
using namespace std;

class Super
{
      protected :
              int a;
      public :
             virtual void Read();
};
void Super :: Read()
{
     cout<<"masukan nilai a : ";
     cin>>a;
}
class Sub : public Super
{
      protected :
              int i, j;
      public :
             void Read();
};
void Sub :: Read()
{
     cout<<"Masukan nilai i : ";
     cin>>i;
     cout<<"Masukan niali j : ";
     cin>>j;
}
int main()
{
    Super *a1 = new Super();
    a1 -> Read();
   
    Sub *a2 = new Sub();
    a2 -> Read();
   
    a1 = new Sub();
    a1 -> Read();
   
    system("pause");
    return 0;
}