VIRTUAL BASE CLASSES

VIRTUAL BASE CLASSES

     An ambiguity can arise when several paths exist to a class from the same base class. This means that a child class could have duplicate sets of members inherited from a single base class. C++ solves this issue by introducing a virtual base class. When a class is made virtual, necessary care is taken so that the duplication is avoided regardless of the number of paths that exist to the child class.

Example:

#include<iostream.h>

#include<conio.h>

 

class student

{

   int rno;

  public:

   void getnumber()

   {

              cout<<"Enter Roll No:";

              cin>>rno;

   }

   void putnumber()

   {

              cout<<"\n\n\tRoll No:"<<rno<<"\n";

   }

};

 

class test:virtual public student

{

  

  public:

   int part1,part2;

   void getmarks()

   {

              cout<<"Enter Marks\n";

              cout<<"Part1:";

              cin>>part1;

              cout<<"Part2:";

              cin>>part2;

   }

   void putmarks()

   {

              cout<<"\tMarks Obtained\n";

              cout<<"\n\tPart1:"<<part1;

              cout<<"\n\tPart2:"<<part2;

   }

};

class sports:public virtual student

{

 

  public:

    int score;

    void getscore()

    {

              cout<<"Enter Sports Score:";

              cin>>score;

    }

    void putscore()

    {

              cout<<"\n\tSports Score is:"<<score;

    }

};

class result:public test,public sports

{

    int total;

  public:

   void display()

   {

      total=part1+part2+score;

      putnumber();

      putmarks();

      putscore();

      cout<<"\n\tTotal Score:"<<total;

   }

};

 

void main()

{

   result obj;

   clrscr();

   obj.getnumber();

   obj.getmarks();

   obj.getscore();

   obj.display();

   getch();

}




Output:




Enter Roll No: 200

 Enter Marks

 Part1: 90

Part2: 80

Enter Sports Score: 80

 Roll No: 200

 Marks Obtained

Part1: 90

Part2: 80

Sports Score is: 80

 Total Score is: 250