Ok... the word ''Bus'' is a concept... embodying a large vehicle, numerous seats, or whatever. Now, see the thing driving down the road full of people? That is an instance of a Bus. An instance is a physical representation of a concept. There can be any number of instances of that concept.

In code terms:

  // This is the Bus concept, embodied as a classclass Bus{int number_of_seats;int colour;int driver;};// Now we make an instance of a Bus, called bus1;Bus bus1;// And another one, called bus2;Bus bus2;  

Note that your original example was incorrect: it doesn''t make sense for driver to be an instance of Bus. Driver is perhaps part of a Bus, but an instance of a Bus is a Bus. With me?

To ''instantiate'' is to ''create an instance''. So, the line "Bus bus1" instantiated a ''Bus'' object called ''bus1''. Just like the line ''int xyz'' instantiates an ''int'' object called ''xyz''.

Is that any help?

It''s quite simple. First you have to create your class :

class bus
{
protected:
const char *driver;
unsigned long seats;
unsigned long capacity;

public:
int showdrivername();
};

But, VC++ can''t use a class in this way, you must create an instance of it. That means the compiler will allocate as for a variable memory to stock the all the data of the class.
In this case, it will allocate memory for the 3 variables (driver, seats, capacity) and for the procedure showdrivername();

You create an instance of a class this way:
for ex: bus *mybus;

This way with your variable mybus, you can use all data members of the class. Ex: mybus->capacity=50;

The class structure is very cool if you have several same objects of the same type. In this case you can have for example 3 buses and assign different value for each one.

Ex:
bus *mybus1;
bus *mybus2;
bus *mybus3;

mybus1->capacity = 100;
mybus2->capacity = 150;
mybus3->capacity = 200;


This is what we call instancing;

hope I was of any help !

quote:Original post by Pixelisator

Ex:
bus *mybus1;
bus *mybus2;
bus *mybus3;

mybus1->capacity = 100;
mybus2->capacity = 150;
mybus3->capacity = 200;

Shouldn''t that be:

bus *mybus1 = new bus;
bus *mybus2 = new bus;
bus *mybus2 = new bus;

No, instantiating a class has access to all the members of the class. Otherwise there''d be no point to protected and private members. It''s other classes that can''t access the protected and private members.

As for the heap issue, well Pixelisator accidentally confused matters by declaring pointers to Buses instead of actual Buses. When you declare a pointer, you generally then have to create the actual object on the heap. But there is no reason you can''t just have a class on the stack.