Screens are called either through transaction codes or using the statement CALL SCREEN. During the call, the event PBO is triggered and its event block is processed in the screen flow logic. Afterwards, the screen of the dynpro (dynamic program) is displayed in the current or in a new pop-up level (in the case of modal dialog boxes). After a user action in the user interface of this window, the event PAI (or POH or POV) is triggered and its event block is processed in the screen flow logic. In the event blocks of the screen flow logic, dialog modules of the appropriate ABAP program are called. When PAI processing is closed, the next screen of the current dynpro (dynamic program) is called.
Each screen has a next screen. In particular, a screen can also have its own special next screen. The next screen is either statically predefined ot it is set in the ABAP program using the statements SET SCREEN or LEAVE TO SCREEN. In this way, a screen is automatically part of a screen sequence. Each next screen always belongs to a single pop-up level and is executed in a single window. The number of the current screen can be taken from the system field sy-dynnr.
The flow of a screen sequence is determined by the respective next screen in the dynpro (dynamic program) concerned. During processing, a screen always has a next screen. At the beginning of processing, this is statically predefined, but it can be overwritten in the program. The first screen of a screen sequence is the initial screen. A screen sequence is ended by calling the next screen with the screen number 0.
If a screen sequence is embedded in another, the calling screen sequence is continued after completion of a screen sequence. If the screen sequence is not embedded, the current program is ended.