This event keyword defines the standard processing block of an executable program. The associated event is triggered by the ABAP runtime environment during the running of an executable program after any standard selection screens have been processed.
In an executable program, all statements that are not declarations and that are listed before the first explicit
or if the program does not contain any explicit processing blocks, then all functional statements of
the program, are assigned to an implicit event block
START-OF-SELECTION, which is inserted before any explicit
START-OF-SELECTION event blocks.
If the program is associated with a
logical database, preparatory tasks can be performed in
before the logical database imports the data. If the program is not associated with a logical database, this event block becomes a type of "main program" from which
procedures or screens are called.
The following are three executable programs with exactly the same functions:
The first program contains an explicit event block
START-OF-SELECTION and shows the recommended spelling.
REPORT test_start_of_selection. DATA text TYPE string. START-OF-SELECTION. text = `Hello World!`. WRITE text.
In the second program, an assignment is inserted before the first processing block, which forms a second implicit event block
START-OF-SELECTION before the explicit event block.
REPORT test_start_of_selection. DATA text TYPE string. text = `Hello World!`. START-OF-SELECTION. WRITE text.
In the third program, there is no explicit processing block. All statements implicitly form the event block
REPORT test_start_of_selection. DATA text TYPE string. text = `Hello World!`. WRITE text.
The third program has exactly the same meaning as the first program. The second program, in contrast, would have the following form if expressed explicitly:
REPORT test_start_of_selection. DATA text TYPE string. START-OF-SELECTION. text = `Hello World!`. START-OF-SELECTION. WRITE text.
This means that if the second program contained a
WRITE statement before
the explicit event block, it would behave differently to the first or third programs with the same
WRITE statement, as the statement
NEW-LINE is executed at the end of the implicit event block.