Pre-Display/Verify
The Pre-Display/Verify event point executes before Pre-Display and again after Verify, except during data addition, when it is not executed prior to displaying the image. After displaying the image, Pre-Display/Verify executes the same number of times as Verify because it always executes after Verify, and never unless Verify has executed.
The primary reason Pre-Display/Verify executes twice is for data that is retrieved from files, and then manipulated and displayed to the screen. It does not execute before Pre-Display during data addition because the data has not yet been entered and stored.
This event point is found only in input processes and the Key Entry image of inquiry processes. It is often used for:
Validating the interrelationships between fields on the screen that a user entered. While APPX automatically validates individual items of information that are stored in a database, it is up to the designer to validate their interrelationships.
Building keys and accessing information that cannot be accessed automatically with a data lookup. For example, you may have to perform calculations or look up data to determine the key of the record to be read.
Flagging error or warning conditions using ERROR, WARNING, and BLINK statements.
Performing computations and accumulations.
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