0, however up to 64k of user numbers can be established, for use when the Applix is serving multiple users, or running as a Bulletin Board. Normally you just ignore this. Files with the address in the directory entry provide a way for small files to load quicker than normal. The BORING bit is provided for you to apply to files which don’t change, such as programs in the /bin directory, therefore removing any need to back them up. Hidden files are for tidy housekeeping when others are using the system, as User 0 will see all files in any case. Symbolic links are for use by Jeremy Fitzhardinge, and allow a file to have multiple names, provided you have an appropriate driver.
1616/OS Commands User Tutorial Manual Page 69