Re: A92: Checksums
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Re: A92: Checksums
David Kühling schrieb:
> Arno Kizina wrote:
>
> > Can anybody tell me the position and perhaps the construction of the
> > checksum in
> > a fargo-program, after I patched a program to run on 256k, graphlink
> > bothered a
> > wrong checksum.
> > Thanks AK
> > Arno.Kizina@t-online.de
>
> The problems with the checksums I had too, when I modified FARGO 0.1.13
> myself
> to run at a 256K TI-92. I get them out by comparing many backups. The
> checksums f .92B
> files are slightly different to those in .92p files, but the method is
> the same. Somewhere
> in the header of the file (at 40h -60h), there is the size of the .92x
> file in bytes (4Bytes in intel's way). The last words in the file are
> a checksum, which is the sum of all bytes in the file from somewhere
> between
> 45h-60h and the end (the checksum is not included to the checksum
> calculation).
> For example, when you change at three positions in the file 02 to 04,
> the checksum
> will become 02*3 bigger. If the last to bytes in the file are listet in
> the hex-editor as
> e.g. FF84, you will have to type 84FF into the hex-calculator (because
> of intel's
> method of storing variables), and add 2*3 = 6 to it. The result is 8505.
> To store it
> in the file you will have to exchange the bytes again -> 0585 (intel's
> method) and write it
> back to the .92x file. (I modified graylib, gray7lib and some other
> programs in this way, manualy
> because the program, I wrote, which adds the checksums to .92b files
> didn't work with
> .92x files)
As I only wanted to correct checksums of programs, I looked at the files with
the aid of my hexeditor and so found that by myself, thanks
>
> P.S. Can you send me please the .zip file of FARGO 0.1.14, because I
> have no one modem,
> and my schools internet connection is switched on very seldom. (I
> don't know, wether my
> modified version of FARGO 0.1.13 completely o.k.)
>
Sorry, but I already deleted the fargo file, and, as the one I made for
myself with a lot of other stuff is more than 400k, I don't want to post it
here. If you want to have it, send me your email-address so that I can mail it
to you privately
AK
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