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.
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