Original Author Paul Laughton, 2011
Page 44
De Re BASIC!
Do not confuse the pointer with the thing it points to. A pointer to a List is not a List; a pointer to a
bitmap is not a bitmap. A pointer is just a number that represents something else.
As an example of pointers think of a file cabinet drawer with folders in it. That file cabinet is maintained
by your administrative assistant. You never see the file drawer itself. In the course of your work you will
create a new folder into which you put some information. You then give the folder to your assistant to
be place into the drawer. The assistant puts a unique number on the folder and gives you a slip of paper
with that unique number on it. You can later retrieve that folder by asking your assistant to bring you
the folder with that particular number on it.
In BASIC! you create an information object (folder). You then give that information object to BASIC! to
put into a virtual drawer. BASIC! will give you a unique number--a pointer--for that information object.
You then use that pointer to retrieve that particular information object.
Continuing with the folder analogy, let's assume that you have folders that contain information about
customers. This information could be things such as name, address and phone number. The number that
your assistant will give you when filing the folder will become the customer's customer number. You can
retrieve this information about any customer by asking the assistant to bring you the folder with the
unique customer number. In BASIC! you would use a Bundle to create that customer information object
(folder). The pointer that BASIC! returns when you create the customer Bundle becomes the customer
number.
Now let's assume that a customer orders something. You will want to create a Bundle that contains all
the order information. Such bundles are used by the order fulfillment department, the billing
department and perhaps even the marketing department (to SPAM the customer about similar
products). Each Bundle could contain the item ordered, the price, etc. The Bundle will also need to
contain information about the customer. Rather than replicate the customer information you will just
create a customer number field that contains the customer number (pointer). The pointer that gets
returned when you create the order bundle becomes the Order Number. You can create different lists of
bundles for use by different departments.
It would also be nice to have a list of all orders made by a customer in the customer Bundle. You would
do this by creating a List of all order numbers for that customer. When you create the customer bundle,
you would ask BASIC! to create an empty List. BASIC! will return a pointer to this empty List. You would
then place this pointer into the customer record. Later when the customer places an order, you will
retrieve that list pointer and add the order number to the List.
You may also want to create several other Lists of order Bundles for other purposes. You may, for
example, have one List of orders to be filled, another List of filled orders, another List of returned
orders, another List for billing, etc. All of these Lists would simply be lists of order numbers. Each order
number would point to the order Bundle which would point to the Customer Bundle.