Function Parameters 
Use
Use the Parameters view to assign parameters to functions (with function reference).
See Also: Example: Creating Functions
Features
ABAP Parameters and External Parameters
A function module can have parameters. If this is the case, you must assign the corresponding ABAP parameters to the associated functions. Parameters that have already been applied are shown. If external names or descriptions of such parameters are changed, then these are valid for all applications of this parameter. You can choose any parameter here except PERIOD_FROM, PERIOD_CNT and CALL_PROG. You then assign each of these to a language-dependent external parameter; use the Explanation column to enter a commentary on the parameters.
Parameter Type and Default Value
The parameter types include:
Normal: The parameter appears without an entry; you must fill the field during template maintenance. Do not enter any values in the Default column.
Hidden: the parameter does not appear on the screen. You need to enter a value in the Default column. This can be a function with field reference or a character string bracketed in quotation marks ( ” ).
Literal field: the entry value of the parameter contains the function name field as a character string; that is, a literal entry. The parameter does not take hold of these contents, but rather the program transfers internally the combination of table fields in quotation as character string. With this parameter type you can enter a field name in column Default .
Optional: A free space (“ “) is shown as parameter in the template maintenance. You can fill the field during template maintenance. Do not enter any values in the Default column. However, you must enter a default value in the associated function module if you do not make any entries during template maintenance.
Using Data Elements for Determining Possible Entries
By using F4 for parameters gives only those functions whose data elements match those of the parameters. You can enter the data element in the F4 data element column, or allow the SAP system to take the data element from the corresponding function module.
If you enter an asterisk ( * ) in the F4 data element column, all functions appear for all instances of the parameter, as long as they are generally available in this context.
For more information, see Function Uses .