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From: binder@asd.DEC.COM ("Exit, pursued by a bear")
Newsgroups: net.micro.apple
Subject: Re: Files not on Catalog
Message-ID: <8610151306.AA20921@decwrl.dec.com>
Date: Wed, 15-Oct-86 11:44:00 EDT
Article-I.D.: decwrl.8610151306.AA20921
Posted: Wed Oct 15 11:44:00 1986
Date-Received: Wed, 15-Oct-86 20:45:00 EDT
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> 	The catalog track is 11 (hex). the T/S list is on track 11
> (hex) sector 00 (hex).
> -- 
> +--------------------------------------------------------------------+
> |      I never make mistakes. I thought I did once, but I was wrong. |
> |UUCP:	...!harvard!bu-cs!bucsb!ilacqua                        |
> |ARPANET: ilacqua@bucsb.bu.edu                                       |
> |CSNET: ilacqua%bucsb@bu-cs      BITNET: engemnc@bostonu             |
> +--------------------------------------------------------------------+

Oops, you've just made your first mistake.  The correct names and locations 
for the components of the Apple DOS cataloguing system are these:

CATALOG:	Occupies track 11-hex/17-decimal, except sector 0.  Begins at
		sector F-hex/15-decimal.  Capable of recording 105 files, 7 in
		each sector.  Each non-empty sector contains a pointer to the
		next, with the last pointer being zeroes.  Successive sectors
		are each one less, numerically, so that the first is at T11-SF,
		the second is at T11-SE, and so on.
		
VTOC:		(Volume Table Of Contents)  Occupies track 11-hex/17-decimal,
		sector 0.  Records DOS version, allocation direction, disk
		size.  Keeps track of used sectors via a bit map.

T/S List:	(Track/Sector List)  Occupies the first sector of each file.
		Lists the locations of successive data sectors of that file. 
		If a file exceeds a certain size, it may contain more than one
		T/S list; the second will be in the middle of the file, after
		the data sectors listed in the first T/S list. 

The standard method of allocation on a fresh disk is to start at track 
12-hex/18-decimal, sector F-hex/15-decimal, and allocate inward toward higher 
track numbers until the end of the disk is reached, and then to begin outward 
allocation at track 10-hex/16-decimal.  The idea is that the catalog 
information will be at the center of the seek range, thereby minimizing the 
overall amount of seeking needed to refer to it.  

To retrieve "hidden" files, you really must have a disk editing utility.  The 
one I use is part of the ANIX package.

Cheers,
Dick Binder   (The Stainless Steel Rat)

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