Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!silver!sl161011
From: sl161011@silver.bacs.indiana.edu (Kevin Clendenien)
Newsgroups: comp.sys.atari.st
Subject: Re: Writing on write-protected disk confirmed
Message-ID: <3523@silver.bacs.indiana.edu>
Date: 24 Mar 89 18:05:37 GMT
References: <1608@orion.cf.uci.edu> <769@snjsn1.SJ.ATE.SLB.COM>
Reply-To: sl161011@silver.UUCP (Kevin Clendenien)
Organization: Indiana University BACS, Bloomington
Lines: 26

In article <769@snjsn1.SJ.ATE.SLB.COM> greg@sj.ate.slb.com (Greg Wageman) writes:
>the file was gone.  I removed the disk from the drive, to look at it,
>and was shocked to discover that even though it was still
>write-protected, the emulator had succeeded in deleting the file!
Greg,
   I have not used the CP/M emulator, so I can only conjecture on this subject,
but it is important to understand a couple of things about the emulator.  It is
possible that the emulator did not actually delete the file, but merely removed
it from the directory of the disk that it keeps in memory.  Thus, when you did
a DIR command, the file was reported as gone because it no longer showed up in
the directory that the OS contained in memory.  Did you at any point after
"deleting" this file, reboot the emulator and then execute a DIR command?  The
rebooting of the emulator would have cleared the directory in memory, and 
forced the emulator to reread the directory from disk, possibly recovering
the "lost" file.  I have been lead to believe that the Atari drives use much
the same mechanism as the IBM 3.5" drives.  If this is the case, and there
is no reason for Atari to have changed the mechanisms themselves (not even
to save money) then there is NO WAY THROUGH SOFTWARE to write to a write
protected disk.  Even if the operating system ignores some signals from
the disk drive, the write protect signal is used internally by the drive, to
allow it to decide whether or not is should executed a write request from
the computer.  The fact that the CP/M emulator returned an error message
leads me to believe that it did not really write to the disk.  
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sl161011@silver.UUCP                                      Kevin B. Clendenien
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