What does the H protection bit mean under classic AmigaOS?

Question

The AmigaOS file protection bits allows for Read, Write, eXecute, Delete permissions on files, similarly to Unix (save for the Delete permission). Additional bits are Archive (reset when a file is written), Pure (signals that the program code is reentrant, thus it can be kept in memory to reduce disk swapping via the RESIDENT command), Script (file is a shell script that can be run without using the RUN command).

There's also an H bit that however has two different historically accounted interpretations for its meaning.

The first interpretation is that it means Hidden; supposedly its effect is to hide the file in a directory listing issued in the shell; the idea was that it would be applied to #?.info files (Workbench icon files) since they're uninteresting for the user. However, this looks unimplemented as neither the DIR nor the LIST command have options to optionally "unhide" hidden files.

The second interpretation is that it means Hold. Supposedly an executable that is both Pure and Hold would automatically become resident after the first time it is executed.

Which of the two interpretations is correct?

Answer 1

The Hold interpretation is the correct one for AmigaOS. In the OFS and FFS file systems, if the H,P, E, and R bits are all set then a reentrant command will automatically become resident the first time its executed.

The confusion comes from the later SFS (Smart File System) which does use it as a "hide" bit despite that not being part of the original standard. If this bit is set on an SFS file system the file will indeed be hidden, but since this wasn't the original intended function there is no switch for the dir or list commands to reveal hidden files meaning you have to remember or infer their presence to access them.