Aesop's Fables IIgs (Unicorn Software, 1986)

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#999 - Reading comprehension and language arts software. 12 stories for children ages 6-9. 1 or 2 players. Skills developed: reading, comprehension, spelling, vocabulary building, alphabetizing, rhyming, contractions, memory building, and computer literacy!

Disk structure
This is a standard 3.5" disk that can be copied with ZZCopy or Photonix II.

Protection type
This is the usual track length protection check on tracks $20 and $21, side 1 (there are both sides on a 3.5" disk: side 0 and side 1). If the length of the track is not within a known range, then we have a copy and the program quits to the launcher.

Searching for the protection
In 2016, I cracked Read and Rhyme and they share the same protection (see http://www.hackzapple.com/phpBB2/viewtopic.php?t=1077). The code is slightly different but I loaded the program AESOP.SYS16 in The Flaming Bird Disassembler and searched for E0 B0 (CPX #$B0) which verifies the track length. I got it in the at $7370. Then, it was a matter of stepping backwards to find the initial call to the protection. It is at $09EF and it stores the result at $1006. If the value is 0, we have an original disk, otherwise we have a copy.

How to crack

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The protection check