At the heart of the AcuODBC interface are data dictionaries that map your application's SQL commands to COBOL records 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 fields are included in the data dictionary and how they are mapped to a database column format that your Windows application will recognize. 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.