In this example, the circulation department of a magazine
maintains a mailing list that contains tens of thousands of names.
Each issue of the magazine contains a form for readers to fill out
when they change their names or addresses. To simplify the maintenance
job, the form requests that readers send only new information. New
subscribers can start a subscription by completing the entire form.
When a form is received, a data entry operator enters the information
about the form into a raw data file. The mailing list is updated once
per month from the raw data file.
The mailing list includes
these variables for each subscriber:
specifies a unique number that is assigned to the subscriber at the time the subscription ...