Dialog Transaction Execution dari kutipan BC402

You assign a dialog transaction to a module pool. The following steps occur when you run a dialog transaction:

• First, the LOAD-OF-PROGRAM event is triggered. Once this event block has been executed, the ABAP processor passes control to the screen processor. For an example of how to use this new event, refer to the example in the Function Groups and Function Modules unit.
  
• The screen processor processes the intial screen specified in the transaction definition. The initial screen can be a selection screen (regardless of the program type). The PROCESS BEFORE OUTPUT event is triggered and control passes to the ABAP processor, which processes the first PBO module.
  
• The ABAP processor executes the processing block and returns control to the screen processor. Once all PBO modules have been processed, the contents of any ABAP fields with identically-named corresponding fields on the screen are transported to the relevant screen fields. Then the screen is displayed (screen contents, active title, active status).
  
• Once the user has chosen a dialog function (such as ENTER), the contents of the screen fields are transported back to the corresponding identically-named fields in the ABAP program, and the processing blocks that belong to the PROCESS AFTER INPUT event are processed. The system then continues by processing the next screen

The only processing logic that is processed in a dialog transaction are the statements belonging to the LOAD-OF-PROGRAM event and those occurring in the various modules.
However, you can also use the statement LEAVE TO LIST-PROCESSING. This makes all of the list processing events available to you.