Passing Data Between Calling Programs and Subroutines

Passing Data Between Calling Programs and Subroutines

The default handling of data is different for internal and external subroutines.

In the case of internal subroutines, you can access all global data of the calling program directly from your subroutine, provided it is not hidden by local data with the same name. This global data consists of internal data objects and types, as well as all ABAP Dictionary fields which are referenced with the TABLES statement in the program (for more information about this statement, see The TABLES Statement).

If you want to access the calling program data from external subroutines in the same way as from internal subroutines, you have to declare the data as common part in the calling program as well as in the programs that contain the external subroutines (see Declaring Data as Common Part).

When you work with global data in subroutines, you can put a copy of the global data on a local data stack. This is valid for global data in internal subroutines and for data declared as common part. To do so, you must work with field symbols (for more details about this topic, see Assigning a Local Copy of a Global Field).

You should use common parts only for simple modularizations. Especially when using function modules in nested subroutine calls (for more information about function modules, see Function Modules), the rules for accessing common parts can become complicated.

To make programs more transparent and flexible, you should choose the following possibility to pass data between calling programs and subroutines:

Specify explicitly the data that you need and may change in internal as well as in external subroutines. To do so, you can use parameters during defining and calling subroutines. These parameters are defined in the <pass> option of the FORM (see Defining Subroutines) and PERFORM (see Calling Subroutines) statements.

The following topics describe

Declaring Data as Common Part

Passing Data by Parameters