Examples of Derived Classes

/************************************************************************
*

                                                                        *
************************************************************************/

// This example illustrates references
// to base class members.

class base
{
public:
      int a,b;
};
class derived : public base
{
public:
      int c;
};
void main()
{
      derived d;
      d.a = 1;      // base::a
      d.b = 2;      // base::b
      d.c = 3;      // derived::c
}

/************************************************************************
*

The derived class can also add new class members and redefine existing base class members. In the above example, the two inherited members , a and b, of the derived class d, in addition to the derived class member c, are assigned values.

For example:

                                                                        *
************************************************************************/

// This example illustrates references to base class
// members with the scope resolution (::) operator.

#include <iostream.h>
class base
{
public:
      char* name;
      void display(char* i) {cout << i << endl;}
};
class derived : public base
{
public:
      char* name;
      void display(char* i){cout << i << endl;}
};
void main()
{
      derived d;                    // create derived class object
      d.name = "Derived Class";     // assignment to derived::name
      d.base::name = "Base Class";  // assignment to base::name

      // call derived::display(derived::name)
      d.display(d.name);

      // call base::display(base::name)
      d.base::display(d.base::name);
}

/************************************************************************
*

In the following example, d, a pointer to a derived class object is assigned to bptr, a pointer to a base class object. A call is made to display() using bptr. Even though bptr has a type of pointer to base, in the body of display() the name member of derived is manipulated:

                                                                        *
************************************************************************/

// This example illustrates how to make a pointer
// to a derived class point to a base class.

#include <iostream.h>
class base
{
public:
      char* name;
      void display(char* i) {cout << i << endl;}
};
class derived : public base
{
public:
      char* name;
      void display(char* i){cout << i << endl;}
};
void main()
{
      derived d;

      // standard conversion from derived* to base*
      base* bptr = &d;

      // call base::display(base::name)
      bptr->display(bptr->name);
}