tut40.cpp

#include <iostream>
using namespace std;

class Student
{
protected:
    int roll_number;

public:
    void set_roll_number(int);
    void get_roll_number(void);
};
void Student ::set_roll_number(int r)
{
    roll_number = r;
}
void Student ::get_roll_number()
{
    cout << "The roll number is  " << roll_number << endl;
}
class Exam : public Student
{
protected:
    float maths;
    float physics;

public:
    void set_marks(float, float);
    void get_marks(void);
};
void Exam ::set_marks(float m1, float m2)
{
    maths = m1;
    physics = m2;
}
void Exam ::get_marks()
{
    cout << "The marks obtained in maths are : " << maths << endl;
    cout << "The marks obtained in physics  are : " << physics << endl;
}
class Result : public Exam {
     float percentage ;
      public :
       void display_results (){
        get_roll_number();
         get_marks();
        cout << " Your percentage is "<<(maths + physics)/2<<endl;         
       }
        
      
};
int main()
{
Result harry ;
 harry.set_roll_number(233);
 harry.set_marks(94.0,90.3);
 harry .display_results();

    return 0;
}