Earlier, we discussed sorting as an important operation in telephone-book publishing. This application is kind of special in that the telephone book is only published once or twice a year, so all the work can be done right before the publishing date.
Consider, on the other hand, the database kept by American Express for tracking ``cardmembers.'' This needs to be much more dynamic.
Each customer has a record: name, customer id number, address, perhaps some billing information (!).
