This technique is shown in Figure H-21. If you examine the figure, you will see that a similar set of links
has been used to represent the relationship between VENDOR BB and its invoices. The structure in Figure H-21 is much easier to modify than is a sequential list of the records. For example, suppose that we
add a new invoice, say number 111, to VENDOR AA. To do this, we just add the record to the file and
insert it into the linked list. Physically, the record can be placed anywhere. But where should it be placed
logically? Usually, the application will have a requirement; for example, children are to be kept in