Pre-Display

In change, delete, and inquire modes the Pre-Display event point executes once, after the Pre-Display/Verify event point and before Global Pre-Display. During data addition Pre-Display/Verify is not executed prior to displaying the image. Instead, Pre-Display is executed once for each entry level (up to 9 times).

Because Pre-Display is an image-level event point, it is used for image-specific routines. Recall that the frame-level event points Select Image and Global Pre-Display can be used for routines that apply to all alternate images.

Pre-Display is found only in menu, input, inquiry, and output processes. It is often used to:

·    Prohibit a user from entering a field by using a NO INPUT statement.

·    Set the value of the predefined field OPTION to perform automatic operations, such as automatically ending an input process.

·    Bypass a record. For example, in an accounts payable invoice maintenance process, you might choose to display only those invoice records that were created in accounts payable, bypassing those that were entered through a purchase orders application. You can do so by conditionally executing the NEXT RECORD option in this event point.

·    Establish various control totals or other computed values for display on an input process image.

·    Display fields with DISPLAY statements.