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From: roy@gitpyr.UUCP (Roy Mongiovi)
Newsgroups: net.micro.pc
Subject: Re: DOS PROMPT command and disk drive
Message-ID: <471@gitpyr.UUCP>
Date: Fri, 14-Jun-85 15:50:36 EDT
Article-I.D.: gitpyr.471
Posted: Fri Jun 14 15:50:36 1985
Date-Received: Sat, 15-Jun-85 07:39:45 EDT
References: <547@alberta.UUCP>
Distribution: net
Organization: Georgia Institute of Technology, Atlanta, GA
Lines: 29

> With this prompt, the command 'a:' activates the floppy drive.  When, by
> mistake, I did this with no floppy in the drive, the cursor homed, and the
> 'drive not ready' message printed. Upon entering 'a' for abort, the cursor
> homed again while the drive spun some more, then the 'drive not ready'
> message was repeated.  The only way to get out of the loop was to
> reset the machine. 

The problem is indeed caused by DOS trying to determine the current directory.
Since IBM in its infinite wisdom decided not to put a door sensor on the PC or
the XT, DOS cannot determine if the media has been changed.  When DOS tries to
determine the current directory string, the device driver return an indication
that it doesn't know if the media has been changed or not, so DOS has to go
read the drive to see if the current directory still exists.  This causes your
disk access and the associated problems.  Hitting the "a" key to abort tries
immediately to generate another prompt, and the cycle repeats.  To get around
the problem without rebooting the machine (and this works ONLY on PC-DOS, the
generic MS-DOS seems to blow it, at least on the Victor 9000) use the "i" key
to ignore the error.  DOS will think that the current directory no longer
exists (I.E. the media has changed), and will put you back in the root
directory and give you your prompt.  On a Victor 9000, the cycle continues
even though the error is ignored, and you HAVE to put a diskette in the
drive.  This may be caused by the Victor 9000 drivers having knowledge of
media being changed since they had the wisdom to put in drive door sensors.
-- 
Roy J. Mongiovi.	Office of Computing Services.		User Services.
Georgia Institute of Technology.	Atlanta GA  30332.	(404) 894-6163
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