#ifndef CLASSES_H
#define CLASSES_H 1

#include <iostream>
using namespace std ;

class BaseClass
{
    public:
        BaseClass ()
        { cout << "BaseClass Constructor: " << endl ;}

        virtual ~BaseClass()
        { cout << "BaseClass Destructor: " << endl ; }

        virtual void foo (const string& s) = 0 ;
} ;


class DerivedClass : public BaseClass
{
    public:
        DerivedClass ()
        { cout << "DerivedClass Constructor: " << endl ;}

        ~DerivedClass()
        { cout << "DerivedClass Destructor: " << endl ; }

        virtual void foo (const string& s)
        { cout << "DerivedClass Foo: " << s << endl ; }
} ;
#endif