Report Programs in ABAP are event-driven programs that are used for displaying a large amount of data. The various events firing will take place in a particular ORDER within a report program. That is:

• Top of page: This event will be triggered by the first ‘write’ statement written in the report. It acts as a page header. By default, the first event triggered will be the ‘load-of-program’, if the ‘write’ statement is not INCLUDED in the report.
• Load-of-program: This event will be triggered when the program of type E(Executable program), M(Module pool), F(Function pool), or S(Subroutine pool) gets loaded. It will be in existence only once per program.
• Initialization: This event is used for initializing the values. This event will be triggered after the ‘load-of-program’ event and before the display of the selection screen.
• At selection-screen output: This event will be triggered just before the display of the selection screen. It is used if you wish to change the screen fields during runtime. It will hide the fields or make them invisible/visible or make them intensified.
• At selection-screen: This event will be triggered processing of selection-screen by the USER. It will be used for checking and validating the inputted values.
• At selection-screen on field: This event will be triggered in the PAI(Process After Input) when data is transferred from PARAMETERS or SELECT-OPTIONS to ABAP. It can be used for validating the user input.
• At selection-screen on value-request: Using this, if a program field is defined with ABAP Dictionary field reference for which possible entries help has been defined, the values from the ABAP Dictionary help will be displayed automatically on calling F4 help for that field by the user.
• Start-of-selection: This event will be triggered on execute button click or F8 button press by the user.
• End-of-selection: This event will be triggered on the execution of the last statement of the start-of-selection event.
• End of page: This event will be triggered each time when the list data reaches the page footer region.