RM/Panels supports three different methods of handling screens in COBOL application programs. In addition to the two common approaches of coding individual fields or accepting an entire screen definition, RM/Panels uses a third approach based on a programming technique called the event loop.
The event loop is common in programming graphical user interfaces. It frees you from having to direct all the activity of complex screens. The basic activities of the screen are performed automatically, but every event is reported to the application program to allow special processing when desired. RM/Panels applies this concept to COBOL screen handling to provide full-screen entry with field level control and a minimum of coding. The three methods are contrasted in the following sections.