How does the Dialog handle user requests? | ABAP Module Programming

- when an action is performed ,the system triggers the PROCESS AFTER INPUT event.The data passed includes field screen data data entered by the user and a function code. A functioncode is a technical name that has been allocated in a screen Painter or Menu Painter to a meny entry,a push button,the ENTER key or a function Key of a screen.An internal work field(ok-code)in the PAI module evaluates the function code,and the appropriate action is taken.