Inherit

#include<iostream.h>

#include<conio.h>

#include<stdio.h>

#define size 5



class student

{

 int rollno;

 char name[20];

 public:

 void input()

 {

  cout<<"\n\nEnter Name                 : ";

  gets(name);

  cout<<"\n\nEnter Roll Number          : ";

  cin>>rollno;

 }

 void display()

 {

  cout<<"\n\nName                       : "<<name;

  cout<<"\n\nRoll Number                : "<<rollno;

 }

};

class mark : public student

{

 float m1,m2,m3;

 public:

 void getdata()

 {

  input();

  cout<<"\n\nEnter marks in Mathematics : ";

  cin>>m1;

  cout<<"\n\nEnter marks in Physics     : ";

  cin>>m2;

  cout<<"\n\nEnter marks in Chemistry   : ";

  cin>>m3;

 }

 void showdata()

 {

  clrscr();

  display();

  cout<<"\n\nMarks in Mathematics       : "<<m1;

  cout<<"\n\nMarks in Physics           : "<<m2;

  cout<<"\n\nMarks in Chemistry         : "<<m3;

  cout<<"\n\nTotal Marks                : "<<compute();

 }

 float compute()

 {

  return (m1+m2+m3);

 }

};

class Grade : public mark

{

 float total,avg;

 char grade;

 public:

 void calc()

 {

  getdata();

  avg = mark::compute()/3;

  total = mark::compute();

  if(avg>=80)

   grade = 'A';

  else if(avg>=60)

   grade = 'B';

  else if(avg>=40)

   grade = 'C';

  else

   grade = 'D';

 }

};

void main()

{

 Grade s[size];

 int i=0;

 clrscr();

 for(i=0;i<size;i++)

 {

  clrscr();

  cout<<"\n\nEnter the details for Student "<<i+1;

  s[i].calc();

 }

 cout<<"\n\nEnter 1 to continue : ";

 cin>>n;

 if(n==1)

  for(i=0;i<size;i++)

  {

   cout<<"\n\nDetails for student "<<i+1;

   mark::showdata();

   cout<<"\n\nAverage                    : "<<avg;

   cout<<"\n\nGrade                      : "<<grade;

 getch();

}