Parameter fields generate prompts that
require the user of a report to enter information before
Crystal Reports can return data. Think of a parameter as a
question that the user needs to answer before the report is generated. The
information users enter, or the way they respond, determines what appears in
the report. For example, in a report used by salespeople, there might be a
parameter that asks the user to choose a region. The report would return the
results for the specific region, instead of returning the results for all of
the regions.
By using parameter fields in formulas,
selection formulas, and in the report itself, you can create a single report
that you can modify whenever your needs change. Parameter fields can also be
used in subreports.