In computer software, a user exit is a place in a software program where a customer can arrange for their own tailor-made program to be called. In the R/3 system from SAP, a user exit is contrasted with a customer exit and allows a customer‘s developer to access program components and data objects within the R/3 system. In R/3, some user exits use Include statements to include customer program enhancements that are called from the program. Other user exits use tables that are accessed through customization.
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Difference between user exits & customer exits:
User exit - A user exit is a three character code that instructs the system to access a program during system processing.
SXX: S is for standard exits that are delivered by SAP. XX represents the 2-digit exit number.
UXX: U is for user exits that are defined by the user. XX represents the 2-digit exit number
Customer exit - The R/3 enhancement concept allows you to add your own functionality to SAP’s standard business applications without having to modify the original applications. SAP creates customer exits for specific programs, screens, and menus within standard R/3 applications. These exits do not contain any functionality. Instead, the customer exits act as hooks. You can hang your own add-on functionality onto these hooks. *-- Mani
The following document is about exits in SAP :-
The
R/3 enhancement concept allows you to add your own functionality to
SAP’s standard business applications without having to modify the
original applications.
SAP
creates user exits for specific programs, screens, and menus within
standard R/3 applications. These exits do not contain any functionality.
Instead, the customer exits act as hooks. You can hang your own add-on
functionality onto these hooks.
Types of Exits
There are several different types of user exits. Each of these exits
acts as hooks where you can attach or "hang" your own add-ons.
Menu Exits
Menu exits add items to the pulldown menus in standard SAP
applications. You can use these menu items to call up your own screens
or to trigger entire add-on applications.
SAP
creates menu exits by defining special menu items in the Menu Painter.
These special entries have function codes that begin with "+" (a plus
sign). You specify the menu item’s text when activating the item in an
add-on project.
Screen Exits
Screen exits add fields to screens in R/3 applications. SAP creates
screen exits by placing special subscreen areas on a standard R/3 screen
and calling a customer subscreen from the standard screen’s flow logic.
Function Module Exits
Function module exits add functions to R/3 applications. Function module exits play a role in both menu and screen exits.
When
you add a new menu item to a standard pull down menu, you use a
function module exit to define the actions that should take place once
your menu is activated.
Function
module exits also control the data flow between standard programs and
screen exit fields. SAP application developers create function module
exits by writing calls to customer functions into the source code of
standard R/3 programs.
These calls have the following syntax:
CALL CUSTOMER-FUNCTION ‘001’.
Field Exits
Field exits allow you to create your own programming logic for any data
element in the Dictionary. You can use this logic to carry out checks,
conversions, or business-related processing for any screen field.
Example: The data element BBBNR identifies a company’s international
location number. You might want to set up your R/3 System so that all
international location numbers are larger than 100.
The field exit concept lets you create a special function module that contains this logic.
You
assign the special function module to the data element BBBNR. You then
assign the module to any programs and screens in which users can add new
international location numbers. When you activate your field exit, the
system automatically triggers your special routine whenever a user
enters a company location number.
You can use "RSMODPRF" program to create field exits.
An example of a user exits :-
MODULE user_exit_0001 INPUT
CASE okcode.
WHEN ‘BACK OR EXIT‘.
CASE sy-dynnr.
WHEN ‘100‘.
SET SCREEN 0.
LEAVE SCREEN.
WHEN ‘200‘.
******************************************************************************
**** Note that you can write any code that satisfy your needs. ****
**** But in this case, this was wrote as a sample code for reference sake. ****
**** And you can test it. ****
******************************************************************************
SET SCREEN 100.
LEAVE SCREEN.
ENDCASE.
ENDCASE.