Passing Data Between Programs 

There are two ways of passing data to a called program:

Passing Data Using Internal Memory Areas

ABAP programs have access to two cross-program memory areas that can be used for passing data.

SAP Memory

SAP memory is a memory area to which all main sessions within a SAPgui have access. You can use SAP memory either to pass data from one program to another within a session, or to pass data from one session to another. Application programs that use SAP memory must do so using SPA/GPA parameters (also known as SET/GET parameters). These parameters can be set either for a particular user or for a particular program at the time of logon using the SET PARAMETER statement. Other ABAP programs can then retrieve the set parameters using the GET PARAMETER statement. The most frequent use of SPA/GPA parameters is to fill input fields on screens (see below).

ABAP Memory

ABAP memory is a memory area that all ABAP programs within the same internal session can access using the EXPORT and IMPORT statements. Data within this memory area remains throughout a sequence of program calls, with the exception of LEAVE TO TRANSACTION. To pass data to a program that you are calling, the data needs to be placed in ABAP memory before the call is made from the internal calling session using the EXPORT statement. The internal session of the called program then replaces that of the calling program. The program called can then read from the ABAP memory using the IMPORT statement. If control is then returned to the program that made the initial call, the same procedure operates in reverse  (see also Storage Media for Data Cluster). If a transaction is called using LEAVE TO TRANSACTION, the ABAP memory and the call stack are deleted. They cannot be used for data transfer.

Since objects belonging to ABAP objects can only be accessed within an internal session, it does not make sense and is therefore forbidden (from a syntax point of view) to pass a reference to an object to a calling program through the ABAP memory.

Filling Input Fields on an Initial Screen

Most programs that you call from other programs have their own initial screen that the user must fill with values. For an executable program, this is normally the selection screen. The SUBMIT statement has a series of additions that you can use to fill the input fields of the called selection screen:

Filling the Selection Screen of a Called Program

You cannot fill the input fields of a screen using additions in the calling statement. Instead, you can use SPA/GPA parameters.

Filling Initial Screens using SPA/GPA Parameters