Function groups are containers for function modules. You cannot execute a function group. When you call an function module, the system loads the whole of its function group into the internal session of the calling program (if it has not already been loaded).
SAPL contains nothing but the INCLUDE statements for the following include programs:
LTOP. This contains the FUNCTION-POOL statement (equivalent for a function group of the REPORT or PROGRAM statement) and global data declarations for the entire function group.
LUXX. This contains further INCLUDE statements for the include programs LU01, LU02, … These includes contain the actual function modules.
The include programs LF01, LF02, … can contain the coding of subroutines that can be called with internal subroutine calls from all function modules of the group.
All of the function modules in a function group can access the global data of the group. For this reason, you should place all function modules that use the same data in a single function group. For example, if you have a set of function modules that all use the same internal table, you could place them in a function group containing the table definition in its global data.
Like executable programs (type 1) and module pools (type M), function groups can contain screens, selection screens, and lists. User input is processed either in dialog modules or in the corresponding event blocks in the main program of the function group. There are special include programs in which you can write this code. In this way, you can use function groups to encapsulate single screens or screen sequences.