Flow Logic

It is the code that processes a screen in SAP. The various event blocks of flow logic are as follows

·         Process Before Output PBO

Code that is executed before the current screen is displayed

·         Process After Input PAI

Code to be executed when the user does any interaction with the screen. At the end of PAI the system goes to the PBO of the next or the current screen

·         Process on Help-Request POH & Process on Value-Request POV

Code to be executed when the user presses F1 or F4 respectively. At the end the system continues with the processing of the current screen 

Syntax of the flow logic statements is similar to ABAP, but all ABAP key words can not be used in the flow logic. The following keywords can be used with the event blocks

·         Module       Calls a dialog module

·         Field          Indicates when screen field contents are transported

·         On             Used with Field

·         Values       Used with field

·         Chain         Start of processing of chain of fields

·         Endchain   End of processing of chain of fields

·         Call            Calls a subscreen

·         Loop          Start of processing of screen table

·         Endloop     End of processing of screen table

To summarize

A Transaction is a collection of screens and ABAP routines, controlled and executed by a dialog processor. Only one module pool can be associated with a transaction.

A module pool is a collection of screens, which are invoked in a pre-defined sequence to complete the task that needs to be performed. 

Now we will learn the concepts described above through an example ...