 Such methods either store the additional information in extra files and directories (classic Mac OS and macOS), or give new semantics to previously unused fields of the FAT on-disk data structures (OS/2 and Windows NT).Mac OS using PC Exchange stores its various dates, file attributes and long filenames in a hidden file called "codice_12", and resource forks (a common Mac OS ADS) in a subdirectory called "codice_13", in every directory where they are used.From PC Exchange 2.1 onwards, they store the Mac OS long filenames as standard FAT long filenames and convert FAT filenames longer than 31 characters to unique 31-character filenames, which can then be made visible to Macintosh applications.