The Field Component
Many statement types require you to specify either one or two field components, in which you enter a field name or value. Categories of field components are as follows:
· A defined field is one that is specified in the data dictionary of the current application, or in another APPX application. For example, ORDER1 CUSTOMER NO might be a defined field in the Order Processing (TOE) application.
· A work field, like a defined field, is also specified in the data dictionary, but is not stored in a file.
· A predefined field specifies any one of APPX’s predefined fields (PDFs). A complete list of the PDFs and a discussion of their nature and use are provided in Chapter 4-7: Predefined Fields and Processes.
· A constant includes any of four types of values, including numeric, alpha, date/time, or logic. Unlike some languages, you do not enclose a constant within quotation marks when you specify it in APPX. In addition to letters and numbers, constants may contain special characters. Refer to the discussion about specifying constant values later in this chapter.
Chapter 4-6: ILF Keyword Reference provides the syntax of each statement and also details the specific categories permitted for each field component. Unless a key field is specifically required, a defined field or work field can be used wherever the syntax calls for a field name. Predefined fields and constants can only be used where explicitly stated.