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From: carlson@gateway.mitre.org (Bruce Carlson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Recovery of deleted files, help!!!
Message-ID: <75885@linus.UUCP>
Date: 25 Oct 89 18:04:12 GMT
References: <36440001@hpindwa.HP.COM>
Sender: news@linus.UUCP
Reply-To: carlson@gateway.mitre.org (Bruce Carlson)
Organization: The Mitre Corporation
Lines: 30

In article <36440001@hpindwa.HP.COM> owenc@hpindwa.HP.COM (Owen Cheung) writes:
>
>A friend of mine accidentially deleted some important files from his floppy.
>Does anybody know any way of recovering these files?  I don't know how the
>MS-DOS file system works, but some of the other file systems that I know
>only marks a bit in the directory when a file is deleted.  Thus, if someone
>knows how the file directory is structured, it would be very easy to
>reset that bit and recover that file.  Does the MS-DOS file system works
>the same way?  Does anybody know any public domain or commercial programs
>that can recover deleted files?  Any help is appreciated.
>
>
>Owen

DOS changes the first letter of the file name to a special character and marks
the file's space as available.  I think the special character is hex E5. 
If you haven't written to the disk since the erasure all the data will still
be there, but you have to do a little work to recover it.  

Norton Utilities has a file unerase program and there are several other 
commercial programs that offer this feature.  I also recall seeing a
public domain program of this type, but I don't remember its name.

If you want to play around with DOS DEBUG you might be able to figure out
how to recover a file.  Use diskcopy to make an exact copy of the erased
disk and then see what you can do about getting the file back.
Peter Norton's book Programmer's Guide to the IBM PC provides a brief 
explanation of how files are stored and what happens when they are erased.

Bruce Carlson