Virtual Base Class – C++.

In class hierarchies we have many common things and  the common code is implemented in a base class. Methods and variables and other objects accessed through multiple-inheritance. Base class have only one instance, there is no ambiguity when accessing these names. So,  virtual base classes offer a way to save space and avoid uncertainties in class hierarchies that use multiple inheritance.

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Example :

#include <iostream.h>

  class Stud_det

      {

          protected:

             int Roll;

             char name[20];

          public:

             void getData();

             void showData();

      };

  void Stud_det::getData()

      {

          cout<<"\n\tRoll No? ";

          cin>>Roll;

          cout<<"\n\tStudent Name? ";

          cin>>name;

      }

  void Stud_det::showData()

      {

          cout<<"\n\n\n\t\tStudent Details";

          cout<<"\n\n\tRoll No:"<<Roll<<"  Name : "<<name;

      }

  class Exam:virtual public Stud_det

      {

          protected:

             int marks[5];

          public:

             void getMarks();

             void showMarks();

      };

  void Exam::getMarks()

      {

          char Sub[5][10]={"Eng","Maths","Phy","Chem","Comp"};

          cout<<"\n\tMarks For\n";

          for(int i=0;i<5;i++)

             {

                 cout<<"\n\t"<<Sub[i]<<"? ";

                 cin>>marks[i];

             }

      }

  void Exam::showMarks()

      {

          cout<<"\n\tMarks Obtained\n";

          char Sub[5][10]={"Eng","Maths","Phy","Chem","Comp"};

          for(int i=0;i<5;i++)

             {

                 cout<<"\n\t"<<Sub[i]<<"  :  "<<marks[i];

             }

      }

  class Extra_Curr:public virtual Stud_det

      {

          protected:

             int Point;

          public:

          void getPoint();

          void showPoint();

      };

  void Extra_Curr::getPoint()

      {

          cout<<"\n\tPoints For Extra Curricular Activites : ";

          cin>>Point;

      }

  void Extra_Curr::showPoint()

      {

          cout<<"\n\tPoints For Extra Curricular Activites : ";

          cout<<Point;

      }

  class Result:public Exam,public Extra_Curr

      {

          public:

             void showResult();

      };

  void Result::showResult()

      {

          int Tmarks=0;

          float Avg=0;

          for(int i=0;i<5;i++)

             {

                 Tmarks=Tmarks+marks[i];

             }

          Tmarks+=Point;

          Avg=Tmarks/5.0;

          cout<<"\n\tTotals : "<<Tmarks;

          cout<<"\n\tAggregrate : "<<Avg;

      }

  int main()

      {

          Result Rs;

          Rs.getData();

          Rs.getMarks();

          Rs.getPoint();

          Rs.showData();

          Rs.showMarks();

          Rs.showResult();

          return 0;

      }