- Unix views the file system as a tree, regardless of how many file systems
and physical devices are involved. Windows models this differently as
volumes (C:, D: etc). Other operating systems may have different models.
- The notions of file creation time, last accessed time, last modified
time and so forth are done differently (and incompatibly) on different
kinds of file system.
- One operating system may simulaneously host multiple types of file
system, so some of the differences are associated with the file system
and not with the operating system per se.
I'm not sure what might be required to have FileSystem work smoothly
with RISC OS as well as Windows/Unix, but I think the effort would be
very worthwhile. Windows and Unix file systems are already very similar,
so the best way to ensure a good level of abstraction is to make sure
that the model also fits file systems such as RISC OS that are not
fundamentally unix-based.
So far I have looked at FileSystem only to the extent needed to get
OSProcess/CommandShell working on Pharo, so I don't know if the above
are really relevant. In any case, I'll be happy to help where I can.