Program:

    #include<iostream.h>
    #include<conio.h>

    class student
    {
    int rollnumber;
    public:
    float m1,m2,m3,m4;
    void getnumber(void)
    {
    cout<<"Enter Roll Number: "<<endl;
    cin>>rollnumber;
    }
    void putnumber(void)
    {
    cout<<"\nRoll number: "<<rollnumber<<endl;
    }
    };
    class marks:virtual public student
    {
    public:
    void getmark(void)
    {
    cout<<"Enter subject1 mark\n";
    cin>>m1;
    cout<<"Enter subject2 mark\n";
    cin>>m2;
    cout<<"Enter subject3 mark\n";
    cin>>m3;
    cout<<"Enter subject4 mark\n";
    cin>>m4;
    }
    void putmark(void)
    {
    cout<<"\nSubject1 mark: "<<m1<<endl;
    cout<<"\nSubject2 mark: "<<m2<<endl;
    cout<<"\nSubject3 mark: "<<m3<<endl;
    cout<<"\nSubject4 mark: "<<m4<<endl;
    }
    };
    class result: virtual public student
    {
    protected:
    float tot,avg;
    public:
    void gettotal(void)
    {
    tot=m1+m2+m3+m4;
    avg=tot/4;
    }
    void puttotal(void)
    {
    cout<<"\nTotal: "<<tot<<endl;
    cout<<"\nAverage: "<<avg<<endl;
    }
    };
    class studdetail:public marks,public result
    {
    char course[10];
    int sem;
    public:
    void getdetail(void);
    void putdetail(void);
    };
    void studdetail::getdetail(void)
    {
    cout<<"Enter semester:"<<endl;
    cin>>sem;
    cout<<"Enter course name:"<<endl;
    cin>>course;
    }
    void studdetail::putdetail(void)
    {
    putnumber();
    putmark();
    cout<<"\nSemester: "<<sem<<endl;
    cout<<"\nCourse Name: "<<course<<endl;
    puttotal();
    }
    void main()
    {
    clrscr();
    studdetail s1;
    s1.getnumber();
    s1.getmark();
    s1.gettotal();
    s1.getdetail();
    cout<<"\n\tStudent Detail";
    s1.putdetail();
    getch();
    }