Virtual function

  

                     Virtual function

Virtual function ppt for knowing about the virtual functions in brief

For ppt click here
https://drive.google.com/file/d/0B66GayMWsBULYzl2bWNhaXo5alk/view

Program of static binding
#include <iostream.h>
#include<conio.h>
class Baseclass
{
protected:
int d;
public:
Baseclass()
{     }
Baseclass(int arg)
{
d=arg;
}
void display()
{
cout<<"Display method of Base class";
cout<<endl<<"d="<<d<<endl;
}
};
class Deriveclass;public Baseclass
{
private:
int k;
public:
Derivedclass()
{
}
Derivedclass(int arg)
{
k=arg;
}
void display()
{
cout<<"\nDisplay method of derived class";
cout<<endl<<"d="<<d<<endl;
cout<<endl<<"k="<<k<<endl;
}
};
void main()
{
//create instance of base class
Baseclass varB(10);
//call display function on instance of base class
varB.display();
Derivedclass varD(20);
vard.display();
}

Output
Display method of base class
d=10
Display method of derived c


Program of dynamic binding

#include <iostream.h>
#include<conio.h>
class Baseclass
{
protected:
int d;
public:
Baseclass()
{     }
Baseclass(int arg)
{
d=arg;
}
virtual void display()
{
cout<<"Display method of Base class";
cout<<endl<<"d="<<d<<endl;
}
};
class Deriveclass;public Baseclass
{
private:
int k;
public:
Derivedclass()
{
}
Derivedclass(int arg)
{
k=arg;
}
void display()
{
cout<<"\nDisplay method of derived class";
cout<<endl<<"d="<<d<<endl;
cout<<endl<<"k="<<k<<endl;
}
};
void main()
{

Baseclass *baseptr;                 //declare pointer to base class
Baseclass varB(10);                //create instance of base class                                             
baseptr->display();                //assign address of base class to pointer
Derivedclass varD(20);
baseptr=&varD;
baseptr->display();
}


Output
Display method of base class
d=10

Program for abstract class

Example of Abstract base class

class Base          //Abstract base class
{
public:
virtual void show() = 0;            //Pure Virtual Function
};

class Derived:public Base
{
public:
void show()
{ cout << "Implementation of Virtual Function in Derived class"; }
};
int main()
{
Base obj;       //Compile Time Error
Base *b;
Derived d;
b = &d;
b->show();
}

Output : Implementation of Virtual Function in Derived class
In the above example Base class is abstract, with pure virtual show() function, hence we cannot create object of base class.