Function modules and function groups

Question

Hi alll
   Can anybody explain me abt function module and function groups...please
Thanks and Regards
vijaya

Answer 1

<b>Function groups</b> 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).
The name of a function group can be up to 26 characters long. This is used by the system to create the components of the group (main program and corresponding include programs). When you create a function group or
function module in the Function Builder [Ext.] , the main program and include programs are generated automatically.
When you create a new function group, the system automatically creates a main program containing two includes. Like any other programs and includes, you can display them in the Repository Browser.
The name of the main program is assigned by the system. This is made up of the prefix SAPL followed by the function group name. For example, the main program for function group SXXX is called SAPLSXXX.
The names of the include files begin with L followed by the name of the function group, and conclude with UXX ( or TOP for the TOP include). The TOP include contains global data declarations that are used by all of the function modules in the function group. The other include file within the main program is used to hold the function modules within the group.
You cannot declare a COMMON PART in a function group. Function groups have their own table work areas (TABLES). Function groups encapsulate data.
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.
For function module, have a look at
http://help.sap.com/saphelp_nw04/helpdata/en/26/64f623fa8911d386e70000e82011b8/content.htm
I hope it helps.
Best Regards,
Vibha