Predefined Fields (PDFs)
In the runtime application, there are a number of fields that 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 other fields in your own applications. You can reference predefined fields in statements, for example, and set the values of some of them (such as ALTERNATE IMAGE NUMBER) to control processing flow. APPX keeps track of the values of predefined fields at all times, and maintains their values automatically.
When you use a predefined field, you designate the application ID with three hyphens (---). APPX interprets the three hyphens as the runtime application. (The actual application ID is 0LA.)