At the heart of the AcuODBC interface are data dictionaries that map the SQL commands sent by your Windows application to COBOL records and/or fields and vice versa. These dictionaries are also called extended file descriptors (XFDs) because they're based on the standard COBOL file descriptors (FDs).
This chapter describes what information is included in the XFD and how it is mapped to a database format that is easily recognized by your Windows application. It also describes how you can take control of the XFDs using directives. Since this material is relevant during compilation, it applies only to COBOL developers.