Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!WSUVM1.BITNET!22149853
From: 22149853@WSUVM1.BITNET (Duane Wessels)
Newsgroups: comp.sys.apple
Subject: Re: recovering lost programs under DOS 3.3
Message-ID: <8806262313.aa22064@SMOKE.BRL.ARPA>
Date: 27 Jun 88 04:22:33 GMT
References: 
Sender: daemon@ucbvax.BERKELEY.EDU
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X-Unparsable-Date: Thu, 23 Jun 88 21:30:33 PLT

First of all, you need a DOS 3.3 sector editor.  The DOS 3.3 VTOC
(Volume Table of Contents) is on track $11 and starts at sector $0F.
Start there with the sector editor and look for the filename.  Continue
looking at sectors $0E, $0D, $0C, etc...  When you find the filename,
look at the three bytes preceeding the first byte of the filename.  The
first of these three is the track number of that files Track/Sector List.
The next byte is the sector of that files Track/Sector list.

Now, look at the Track/Sector list at the track and sector found above.
I don't know what this will look like.  Hopefully when the 'empty file'
was saved, DOS didn't clear this list.  If it did, you will have to go
through all the sectors on the disk, looking for the Basic file.  If you
have a sector editor that will scan the disk for text strings, you can
scan it for something that was inside the quotes of a PRINT statement.

It may be that DOS wrote "00" over the first pairs of the Track/Sector
list and left the rest intact.  The first Track/Sector pair where the
file is stored at is at $0C and $0D (12th & 13th bytes) of the Track/
Sector List.  The next pair is at $0E and $0F, etc...

IF you do manage to recover the data, it still may not show up when
you LOAD it.  I think Applesoft files are essentially saved as binary
files, but always start at $801 (??).  Since the first couple of
sectors of the file may have been erased, it would load '00's starting
at $801.  When you LIST a file, it looks at certain memory locations
for the place of the next line.  If it finds '00's, it may just stop
listing.

I hope this isn't more confusing than helpful.  If you can, look at
Appendix C of "The DOS Manual."

Good luck!

+---------------------------------------------------------------------+
| Duane Wessels    Bitnet: 22149853@WSUVM1                            |
|                                                                     |
| "...my parents forgot to pay the gravity bill."  -- Calvin          |
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