Write a C++ Program to illustrate Abstract Base Class

The word polymorphism means having many forms. Typically, polymorphism occurs when there is a hierarchy of classes and they are related by inheritance.

C++ polymorphism means that a call to a member function will cause a different function to be executed depending on the type of object that invokes the function.

Virtual Function : :

A virtual function is a function in a base class that is declared using the keyword virtual. Defining in a base class a virtual function, with another version in a derived class, signals to the compiler that we don’t want static linkage for this function.

Below is the source code for C++ Program to illustrate Abstract Base Class which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/*  C++ Program to illustrate Abstract Base Class  */

#include <iostream>
using namespace std;

class Polygon {
  protected:
    int width, height;
  public:
    void set_values (int a, int b)
      { width=a; height=b; }
    virtual int area (void) =0;
};

class Rectangle: public Polygon {
  public:
    int area (void)
      { return (width * height); }
};

class Triangle: public Polygon {
  public:
    int area (void)
      { return (width * height / 2); }
};

int main ()
{
  Rectangle rect;
  Triangle trgl;
  Polygon * ppoly1 = &rect;
  Polygon * ppoly2 = &trgl;
  ppoly1->set_values (4,5);
  ppoly2->set_values (4,5);
  cout<<"\nExample to illustrate Abstract Base Class :: \n\n";
  cout << ppoly1->area() << "\n";
  cout << ppoly2->area() << "\n";
  return 0;
}

OUTPUT : :

/*  C++ Program to illustrate Abstract Base Class  */

Example to illustrate Abstract Base Class ::

20
10

Process returned 0

Above is the source code and output for C++ Program to illustrate Abstract Base Class which is successfully compiled and run on Windows System to produce desired output.