Using Predefined Fields (PDFs) in Statements
In the runtime application, APPX includes and maintains a number of fields called predefined fields or PDFs. These fields contain various “points of reference,” such as who the current user is and the company address. Although the names of these fields are pre-specified, you can use them as you would any field that you defined in the data dictionary of your own applications. The primary difference between predefined fields and those you specify in the data dictionary is that APPX initializes the values of PDFs and automatically maintains these values at all times. As a designer, you can set or modify the values of certain PDFs with statements, and may thereby alter this pattern of automatic maintenance. Within the context of statements, you can examine the value of a PDF at any point in time, modify a PDF’s value (if allowed), and display a PDF in a report or on a screen image.
There are five categories of predefined fields:
· Current status PDFs provide information about current values, such as the current user ID.
· Process control PDFs control what will happen next in the application.
· Terminal management PDFs provide information about such factors as current cursor position.
· Report management PDFs provide information about the disposition of reports, such as the print destination.
· General purpose PDFs are used as index work variables or work fields in ILF statements.
Each PDF has a number of attributes that uniquely define how it is initialized and maintained by APPX. A table of PDFs and a complete description of each can be found in Chapter 4-7: Predefined Fields and Processes.