Program to illustrate 'const' Objects

#include <iostream.h>
#include<conio.h>
class sample
{
        int a, b;
    public:
        sample(int, int);
        sample() { }
        void display() const; // 'const' member function prototype
        ~sample() { }
};
sample::sample(int x, int y)
{
    a = x; b = y;
}
void sample::display() const // 'const' member function defined
{
    cout << "a = " << a << "\t";
    cout << "b = " << b << "\n";
}
void main(void)
{
    clrscr();
    const sample A(10,20);     // 'const' Object declaration
    A.display();                   // 'const' object invoking 'const' member function
    getch();
}