Designing Interactive Panels (Panel Services) › About Panel Services › Invoke Full-screen Panels › Synchronous and Asynchronous Panel Displays

Synchronous and Asynchronous Panel Displays

An NCL procedure can issue an asynchronous panel statement or a synchronous panel statement:

• Asynchronous panel statements provide a panel display, but the procedure continues execution without waiting for input from the terminal.
• If a synchronous panel is displayed, further processing of the NCL procedure stops until you press an Enter key, a Function key, or provide some other input from a light pen or cursor select key. Control then returns to the NCL procedure following the &PANEL statement. The NCL procedure can then process the data just entered from the terminal.

If a synchronous panel has been displayed for a specific length of time without input from an operator, control can be returned to an NCL procedure automatically. The default panel operation is synchronous.

Note: The synchronous state is simpler to understand than asynchronous, and descriptions of panel operations assume synchronous operation unless stated otherwise.