Pure virtual destructor

#include<iostream>
using namespace std;

class Base
{
    public:
    virtual ~Base() = 0;     // Pure Virtual Destructor
};

// Definition of Pure Virtual Destructor
Base::~Base() 
{ 
    cout << "Base Destructor\n"; 
} 

class Derived:public Base
{
    public:
    ~Derived() 
    { 
        cout<< "Derived Destructor\n"; 
    }
}; 

int main()
{
    Base* b = new Derived;     // Upcasting
    delete b;
}