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From: Jack Klein <jackklein AT spamcop DOT net>
Newsgroups: comp.os.msdos.programmer,comp.os.msdos.djgpp
Subject: Re: Creating a copy protected floppy
Date: Thu, 14 Jul 2005 23:16:55 -0500
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On Thu, 14 Jul 2005 08:32:20 +0300, Ari Lukumies
<nospam DOT ari DOT lukumies AT gmail DOT com DOT invalid> wrote in
comp.os.msdos.programmer:

> RetroMIDI wrote:
> > It is possible to write EXTRA sectors on a particular track so that the
> > sector numbers are within the data sections of lower numbered sectors.
> 
> You do not need to mess the sectors up this way, however, if you don't 
> want to. An easy way to "hide" some of your data (although not so hard 
> to get around with, either) is to format a disk with more than the 
> standard number of sectors on tracks (and with more tracks), while 
> retaining the standard DPB (disk parameter block), so a "normal" copy 
> program only copies the standard sectors and tracks, ignoring the 
> nonstandard ones. For those interested, see Ralf Brown's interrupt list,
> 
> http://www.ctyme.com/intr/cat.htm
> 
> especially the DPB:
> 
> http://www.ctyme.com/intr/rb-2445.htm
> 
> -atl-

There were some commercial companies that got themselves into a lot of
trouble years ago doing that.

I can't remember for sure if it was the original IBM PC, or the PC Jr,
but one of them had a floppy disk drive with enough stroke on the head
to be able to read and write 41 tracks instead of the normal 40 on a
floppy.

Some companies put their own custom, non-standard format and some data
on that extra innermost track.  If an (unknowing) user used the
standard diskcopy to try and make a program disk for a friend, only
the normal 40 tracks were copied.

When the program started, it used either BIOS or direct hardware
access to the disk controller to read the extra track.  If the disk
was a copy, the data wasn't there and the program would not run.

Then IBM changed suppliers for the disk drive in that particular
computer, and the new disk drive did not have the extra stroke to read
the 41st track...

Wasn't is Lotus who used to use a laser to burn a hole at a particular
spot on the program disk?

-- 
Jack Klein
Home: http://JK-Technology.Com
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