• Types of ABAP Processing Blocks
  All ABAP programs are made up of processing blocks. You cannot nest processing blocks. When a program is executed, its processing blocks are called. All of the statements in an ABAP program, apart from its global data declarations, belong to a processing block.

• Dialog Module: Defined between the MODULE...ENDMODULE statements in type 1, M, and F programs. Has no local data area and no parameter interface. Called using the MODULE statement in screen flow logic. Processes screens.
• Event Block: Defined by one of the event key words. N o local data area and no parameter interface.  Reacts to events in the ABAP runtime environment. (Exceptions: AT SELECTION-SCREEN and GET are implemented internally using subroutines, and have a local data area).

Reporting events

• INITIALIZATION
• START-OF-SELECTION
• GET
• END-OF-SELECTION

Called by the ABAP runtime environment while a type 1 program is running; contain application logic for report programs.

Selection screen events

• AT SELECTION-SCREEN OUTPUT
• AT SELECTION-SCREEN ON VALUE REQUEST
• AT SELECTION-SCREEN ON HELP REQUEST
• AT SELECTION-SCREEN ON <f>
• AT SELECTION-SCREEN ON BLOCK
• AT SELECTION-SCREEN ON RADIOBUTTON GROUP
• AT SELECTION SCREEN
• AT SELECTION SCREEN ON END OF <f>

Called by the ABAP runtime environment following a user action on a selection screen in a type 1, M, or F program; process selection screens.

List events

• TOP-OF-PAGE
• END-OF-PAGE
• AT LINE-SELECTION
• AT PF<nn>
• AT USER-COMMAND

Called by the ABAP runtime environment while a list is being created or after a user action on a list in a type 1, M, or F program.

• Procedures: ABAP contains the following procedures. They have a local data area and a parameter interface:

• Subroutines: Defined by FORM...ENDFORM in any program except for type K; called using the PERFORM statement in any ABAP program.
• Function modules: Defined by FUNCTION...ENDFUNCTION in type F programs; called using CALL FUNCTION from any ABAP program.
• Methods: Defined by METHOD...ENDMETHOD in global classes in programs with type K, or in local classes in any ABAP program; called using CALL METHOD from any ABAP program for global classes, and, for local classes, from the program in which the class is defined.

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