Function modules are procedures that are defined in function groups (special ABAP programs with type F) and can be called from any ABAP program. Function groups act as containers for function modules that logically belong together. You create function groups and function modules in the ABAP Workbench using theFunction Builder.
Function modules allow you to encapsulate and reuse global functions in the R/3 System. They are stored in a central library. The R/3 System contains a wide range of predefined function modules that you can call from any ABAP program. Function modules also play an important role indatabase updates and in remote communications between R/3 Systems or between an R/3 System and a non-SAP system.
Unlike subroutines, you do not define function modules in the source code of your program. Instead, you use theFunction Builder. The actual ABAP interface definition remains hidden from the programmer. You can define the input parameters of a function module as optional. You can also assign default values to them. Function modules also support exception handling. This allows you to catch certain errors while the function module is running. You can test function modules without having to include them in a program using the Function Builder.
TheFunction Builder also has a release process for function modules. This ensures that incompatible changes cannot be made to any function modules that have already been released. This applies particularly to the interface. Programs that use a released function module will not cease to work if the function module is changed.
Function Groups Calling Function Modules Creating Function Modules