Re: A82: Checksums and modules


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Re: A82: Checksums and modules



At 07:37 PM 10/21/97 EDT, you wrote:
>In a message dated 97-10-21 18:46:12 EDT, you write:
>
>> SQRXZ for the 86 has the ability to add on modules.  I want to have the
>>  same ability in the 82 version.  I know how to create a checksum to find
>>  such modules, but I don't know how an 82p file is laid out.  Especially
the
>>  checksum that is changed so that the calc will accept the program.  I
don't
>>  want the levels to appear in ASH but only in the PRGM delete menu and
>>  inside SQRXZ itself.  Any help is appreciated.
>
>Well, if the first byte of a level is anything but $00, it will not show
up in
>the Ash menu.  I recommend using a different value, such as $26, $2C, $63,
>$7E, $AA, $BB, $EB, or $EF.  Those are all the values not used by the
>calculator.
>Good Luck,

Sorry I didn't make myself clear the first time.  What I'm asking is how to
figure the checksum the calc uses to determine if a PRGM is okay to accept
through the link cable.  Also, how would you go about reserving and
removing space in the RAM for modules such as these?  I want to be able to
create levels on the 82, compress them, and then use my link cable to
transfer them between computer and calc.

BTW, can anyone give me a list of compression algorithms that have been
used for the 82 (and how well they do it)?  My best algorithm can currently
compress 50 bytes (SQRXZ world) down to 11 bytes (78% compression) using
PCX bitmap style compression.


                 Thomas J. Hruska -- thruska@tir.com
Shining Light Productions -- "Meeting the needs of fellow programmers"
         http://www.geocities.com/SiliconValley/Heights/8504
                    http://shinelight.home.ml.org


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