Run Time Polymorphism in C++ with example

Run Time Polymorphism is usually achieved through the use of inheritance and virtual functions.

Virtual functions essential and capable of supporting run-time polymorphism whenever utilized by using a pointer.

Example:

#include<iostream.h>

#include<conio.h>

class A

               {

                              Public:

                              virtual void show ();

               };

void A :: show ()

{

               cout<<”Base Class”;

}

class B public A

               {

                              Public:

                              void show ();

               };

void B :: show ()

{

               cout<<”Derived Class”;

}

void main ()

{

               clrscr ();

A *ptr;

               A ab;

               B ba;

               ptr = &ab;

ptr -> show ();

ptr = &ba;

ptr -> show ();

getch ();

}

Pure Virtual Function and Abstract class with Example

Pure Virtual Function

A Pure Virtual Function is a type of function which has only a function declaration. It does not have the function definition. The virtual function may be equated to zero.

In other words, any virtual function which is defined in the following manner in the base class is known as Pure Virtual Function.

virtual return_datatype functionname () = 0;

Abstract class

An abstract class is a class that is designed to be specifically used as a base class. Any class which has a pure virtual function is known as Abstract class and we cannot create the object of this class.

Example:

#include<iostream.h>

#include<conio.h>

class media                        //class media is Abstract class

               {

                              public:

virtual void show () = 0;

               };

class book : public media

{

                              char title[20];    

                              char tag[20];

                              double price;

                              public:

                              void get ();

                              void show ();

};

void book :: get ()

{

cout<<”Enter Book Title”;

               cin>>title;           

               cout<<”Enter Book Tag”;

               cin>>tag;

               cout<<”Enter Book Price”;

               cin>>price;

}

void book :: show ()

{

cout<<”Title =”<<title<<”\n”;

cout<<”Tag =”<<tag<<”\n”;

cout<<”Price =”<<price<<”\n”;

}

class tape : public media

{

                              char t[20];

                              char ta[20];

                              double pri;

                              public:

                              void getdata ();

                              void show ();

};

void tape :: getdata ()

{

cout<<”Enter Tape Title”;

               cin>>t;  

               cout<<”Enter Tape Tag”;

               cin>>ta;

               cout<<”Enter Tape Price”;

               cin>>pri;

}

void tape :: show ()

{

cout<<”Title =”<<t<<”\n”;

cout<<”Tag =”<<ta<<”\n”;

cout<<”Price =”<<pri<<”\n”;

}

void main ()

{

               clrscr ();

               media *m;

               book b;

               tape t;

               m = &b;

               b.get ();

               m -> show ();

               m = &t;

               t.getdata ();

               m -> show ();

getch ();

}