You enter data in SAP input screens in all business processes which are modelled in test cases. They are used to create master data, documents, orders, etc. To make test cases flexible, it is better to parameterize these input fields rather than use constants, and to perform calculations with these parameters or variables where appropriate.

Almost all CATT functions require input values and return results. Examples:

• Transaction call and function module call with dialog
  Screen field entries result in database changes. The result of the transaction can be, for example, the return of a success message with master record or document number.
• Function module call
  A function module performs a function (e.g. determine fiscal year), whose result is returned in an export parameter.
• Check customizing or database table contents
  The key for reading a table entry can be assembled from variables. Checking field contents against values which you provide returns a positive or negative result.
• Refer to a test case
  You pass data to a referred test case in constants, parameters or variables. They can be used, e.g. for conditions or as input values for the transaction to be tested.
  The referred test case usually returns a result which can be read in its export parameters by the referring test case.

• Special variables: