These are implemented in the form of subroutines and hence are also known as FORM EXITs. The user exits are generally attached to the standard program by the SAP.
User exits are a type of system enhancement that was originally developed for the R/3 SD (Sales and distribution) module.
User-exits are empty subroutines that SAP Developers have provided for you.
You can fill them with your own source code. Technically this is a modification.All User exits start with the word USEREXIT_...FORM USEREXIT_XXXX....ENDFORM.
User exits can be found in the following ways:
Go to Object Navigator (SE80), select Package and put VMOD (Application development R/3 SD customer modification) and press enter. You will find all the includes for user exits in SD. You will get User exits for Sales order, Delivery, Billing, Pricing etc. Most of the time documentation is maintained for each subroutine which helps developer for better understanding of the subroutine. Select the subroutine according to the requirement and start coding within the subroutine.
- In User exits MV45AFZZ(Sales Order Exit), we have subroutine
This user exit can be used to move additional fields into the communication table which is used for pricing. TKOMK for header fields and TKOMG for item fields. The fields which are not in either of the two tables KOMK and KOMP cannot be used in pricing.
-In User exits MV50AFZ1(Delivery Exit), you have subroutine
This user exit can be used for changes or checks, before a document is saved.