Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!dlyons
From: dlyons@Apple.COM (David A Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: Notes and Comments - Apple II, 18k file
Message-ID: <53680@apple.Apple.COM>
Date: 5 Jun 91 23:02:24 GMT
References: <1991Jun5.031630.10666@crash.cts.com>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 40

In article <1991Jun5.031630.10666@crash.cts.com> mlyons@pro-fla.cts.com (mlyons, SysAdmin) writes:
>
>| Notes and Comments  -  Apple II 
>| Dedicated to the Deprived Apple II Users Everywhere,  June 1991
>'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
[...]
>Another big rumored feature is the use of more FSTs. FST stands for File
>System Translator. Currently GS/OS can't understand ProDos. In order to
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>make all of your Apple ProDos disks work, GS/OS uses a FST for ProDos. The
>FST explains to GS/OS what a ProDos disk looks like, how files and
>directories are stored on the disk, and how to read and write to the disk.
>[...]

The above is essentially right, but it's a little misleading.

Under GS/OS, File System Translators are responsible for all knowledge of
particular volume formats, such as ProDOS and High Sierra (for which there
are FSTs), as well as MFS, HFS, MS-DOS, Apple II DOS 3.3, Apple II Pascal
(FSTs for these could conceivably be part of future system software).

GS/OS delegates tasks to the proper FSTs, and the FSTs do them (they do not
explain to GS/OS what needs to be done).  And the actual reading and writing
of disks is handled by device drivers.

By the way, FSTs have direct knowledge of most application-level GS/OS calls;
when new calls or new optional parameters are added to the GS/OS application
interface, all FSTs need to be revised accordingly.  This is an big reason
that there are no specs on "how to write an FST."

(The remaining advantage of FST modularity is that you can include whatever
collection of FSTs you need, without wasting RAM or disk space with ones
you don't need.)
-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II System Software Engineer         |   P.O. Box 875
America Online: Dave Lyons                |   Cupertino, CA 95015-0875
GEnie:DAVE.LYONS  CompuServe:72177,3233 Internet:dlyons@apple.com

My opinions are my own, not Apple's.