A Dedicated File (DF) is a file directory in the file system of a smart card
. The file directory is identified by the DF name, which is supplemented by the File Identifier (FID). The DF name can be between 1 and 16 bytes long and can contain a registered Application Identifier
(AID), which allows a worldwide unique identification. The Dedicated File is one of several file structures, the others being the Master File (MF), which forms the basis for the basic file structure, and the Elementary File (EF), which contains the user data.