What are the events in Screen Programming?

PBO (Process Before Output) – Before the screen is displayed, the PBO event is processed.
PAI (Process After Input) – When the user interacts with the screen, the PAI event is processed.
POH (Process On Help) - are triggered when the user requests field help (F1). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.
POV (Process On Value) - are triggered when the user requests possible values help (F4). You can program the appropriate coding in the corresponding event blocks. At the end of processing, the system carries on processing the current screen.