d_customer in the library).</p>

<p>Next we have the actual Output. In this case we don't want to do anything in Output so we set this member to false.  Output could be defined as a method that takes data, which is the output record, and returns a format to print.</p>

<p>In After_invoice, we use the Append method to add a format to the end of the report, this time it is another QueryFormat for the line items.  Notice how the data gets passed to the Query method of the QueryFormat.  This time the Output is 