class example in c++

#include<iostream.h>
#include<conio.h>
class book
{
    int bid;
    int balance;
    int received;
    int sold;
    public:
    void getdata()
    {
        cout<<"\nEnter Book Id: ";
        cin>>bid;
        cout<<"\nEnter inventory balance at the begining of the month : ";
        cin>>balance;
        cout<<"\nNumber of copies received during the month : ";
        cin>>received;
        cout<<"\nNumber of copies sold during the month : ";
        cin>>sold;
    }
    void display()
    {
        cout<<"\nBook Id: "<<bid;
        cout<<"\nUpdated Balance : "<<balance;
    }
    void update()
    {
        balance=balance+received-sold;
    }
};
void main()
{
    book b[5];
    clrscr();
    for(int i=0;i<5;i++)
    {
        b[i].getdata();
        b[i].update();
        b[i].display();
    }
    getch();
}