Path: utzoo!attcan!uunet!samsung!think!snorkelwacker!apple!dlyons
From: dlyons@Apple.COM (David A. Lyons)
Newsgroups: comp.sys.apple
Subject: ProDOS 8 programs and extended files
Message-ID: <36850@apple.Apple.COM>
Date: 29 Nov 89 07:18:02 GMT
References: <1101@mountn.dec.com> <1152@umigw.MIAMI.EDU> <3879@puff.cs.wisc.edu> <1161@umigw.MIAMI.EDU>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 28

I've lost track of who said what in all this quoting, but certainly
ProDOS 8 programs *can* support extended files on ProDOS disks if they
want to go to the extra trouble.  The file-oriented MLI commands
don't support extended files, but you can get at them using READ_BLOCK
and WRITE_BLOCK.

It isn't generally recommended, and it isn't trivial, but the format
of extended files on ProDOS disks is documented in ProDOS 8 Technical
Note #25, dated April 1989 (the last section, "Storage Type 5", is the
relevant one).

As I understand it, Copy II Plus *already* does direct block access
for most or all of its operations, so this would be less trouble
than adding extended-file support to a program that does all of its
stuff through the regular file-oriented MLI commands.

[I don't want to make block-level access sound -good- here, though:
one down-side is that there is -no- compatibility with AppleShare
file servers if you do everything at the block level.]
-- 

 --David A. Lyons, Apple Computer, Inc.      |   DAL Systems
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   My opinions are my own, not Apple's.