Path: utzoo!utgpu!attcan!uunet!pyrdc!pyrnj!rutgers!iuvax!silver!creps
From: creps@silver.bacs.indiana.edu (Steve Creps)
Newsgroups: comp.sys.ibm.pc
Subject: Re: screwed up directories on floppies
Message-ID: <2071@silver.bacs.indiana.edu>
Date: 30 Jul 88 00:07:15 GMT
References: <1060@ndsuvax.UUCP> <6332@uwmcsd1.UUCP>
Reply-To: creps@silver.UUCP (Steve Creps)
Organization: The Yankee Horde
Lines: 28

In article <6332@uwmcsd1.UUCP> len@csd1.milw.wisc.edu (Leonard P Levine) writes:
>From article <1060@ndsuvax.UUCP>, by ncperson@ndsuvax.UUCP (Missing Person):
>> Can anyone tell me why DOS will sometimes overwrite the directory of 
>> obe floppy with that of another?
...
>>  it seems to simply be replacing the directory information with a copy of 
>> what was on the previously inserted disk. I've heard of this happening before,
>If you were working with a 1.2 meg floppy, the problem is with the inability
>of your system to detect the removal of the media.
>for the 360K drive, the system will not recheck the directory if you reuse the
>disk in less than 2 seconds from the last use.  Are you working that fast?

   I believe this is actually a bug (or inconvenience) in DOS. I've also seen
this happen before, usually when the disks were changed before exiting
whatever program happened to be running at the time. At least, in my opinion
it was an unfortunate choice to allow DOS to buffer changes to the disk
directory, which I would guess is what is happening to cause the problem.
   As for the system being able to detect a disk change, this feature is not
present in PCs or XTs. According to Norton's programmer's guide, DOS interrupt
13H service 16H is specific to ATs. The reason I note this is because when
I've seen this happen, it has been on a PC or XT.
   Comments welcome, a lot of what I've just said is hypothesis.

-	-	-	-	-	-	-	-	-	-
Steve Creps, Indiana University, Bloomington, home of the "Hoosiers"
	creps@silver.bacs.indiana.edu (192.12.206.2)
	{inuxc,rutgers,pyramid,pur-ee}!iuvax!silver!creps
	creps@iubacs.bitnet (forwarded)