Public Data members of the class in C++

public member of the class can be accessed in class itself, its derived class
and outside of the class. This example shows the same.
#include<iostream.h>
#include<conio.h>
class demo1
{
public:
int a,b,c;
void add()
{
a=10; // public members a,b and c are accessed within the class
b=20;
c=a+b;
cout << c <<endl;
}
};
class demo2: public demo1
{
public:
void sub()
{
a=30; // public members of the class are accessed in its derived class.
b=20;
c=a-b;
cout << c <<endl;
}
};

main()
{
clrscr();
demo2 d;
d.add();
d.sub();
d.a=50; // public members of the class are accessed outside of the class.
d.b=60;
d.c=d.a+d.b;
cout << d.c <<endl;
getch();
}