That's no fun. I can set up a wikidot site pretty easily. I did a fairly basic one for otcalc.wikidot.com.

This is pure speculation, but it would appear that the Prizm has 61 KB of RAM. If you calculate the bytes, that works out to an address of F400. The hex surrounding that address is:

...
0000F3A0:  73 8E 73 8E 7B CF 73 8E 73 8E 7B CF 73 8E 73 8E
0000F3B0:  0D 0A 7B CF 73 8E 73 8E 7B CF 73 8E 73 8E 7B CF
0000F3C0:  73 8E 0D 0A 73 8E 7B CF 73 8E 73 8E 7B CF 73 8E
0000F3D0:  73 8E 73 8E 0D 0A 7B CF 73 8E 73 8E 7B CF 73 8E
0000F3E0:  73 8E 73 8E 73 8E 0D 0A 7B CF 73 8E 73 8E 73 8E
0000F3F0:  7B CF 73 8E 73 8E 73 8E 0D 0A 73 8E 73 8E 73 8E
0000F400:  73 8E 6B 4D 42 2E 21 2E 2E 2E 0D 0A 2E 2E 2E 2E
0000F410:  2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 0D 0A 2E 2E
0000F420:  2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 0D 0A
0000F430:  2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E
0000F440:  0D 0A 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E
0000F450:  2E 2E 0D 0A 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E
0000F460:  2E 2E 2E 2E 0D 0A 2E 2E 2E 2E 2E 2E 2E 2E 2E 2E
...


That may not be very clear, so here's the ASCII equivalent:

...
0000F3A0  sŽsŽ{ÏsŽsŽ{ÏsŽsŽ
0000F3B0  {ÏsŽsŽ{ÏsŽsŽ{ÏsŽ
0000F3C0  sŽ{ÏsŽsŽ{ÏsŽsŽsŽ
0000F3D0  {ÏsŽsŽ{ÏsŽsŽsŽsŽ
0000F3E0  {ÏsŽsŽsŽ{ÏsŽsŽsŽ
0000F3F0  sŽsŽsŽsŽkMB.!...
0000F400  ................
0000F410  ................
0000F420  ................
0000F430  ................
0000F440  ................
0000F450  ................
0000F460  ................
...

@z80man: On the fx-9860G, the addins and the OS used a similar checksum. IIRC, the checksum for the addins on the fx-9860G was simply a sum of some 32 bytes in the header. For reference, here are the specs of the fx-9860G header: http://www.casiocalc.org?s=&showtopic=2622&view=findpost&p=36912. For the OS, it was just a sum of all the bytes in the OS placed into a 4 byte integer at the end of the OS image.

Yeah they say on their site it has 61 KB of user RAM. Are we sure that it's not just user RAM though?

Yes, you have 61KB of storage for your BASIC programs.

Some bad news:

Thank you for sending e-mail.

Also we appreciate for your running of a website for Casio scientific
calculators.
However we regret to say that Casio has no schedule for releasing a SDK for Prism
as for now.

This attractive model, developed as new education equipment, we are suggesting
new function and specification which were not able to achieved by previous
graph function.

Especially Picture Plot Function, it is favored so much, we are going to spread
more useful functions in our website contents as needed.
We would highly appreciate for your effectively usage and continued patronage
of our products.

Best regards

I guess they really don't have plans for a SDK. This came directly from their headquarters in Japan.

But if the header format get cracked, we'll be able to run our own custom code on the Prizm and we can figure out how to program it ourselves.

Has anyone been able to successfully run a modified add-in on the Prizm yet? I can't really understand if the checksum(s) have been figured out already...

.g1a: fx-9860 add-in.
.g3p: fx-CG10/20 picture file.
.g3b: fx-CG10/20 animation file.
.g3a: fx-CG10/20 add-in.

.g3b:
AA AC BD AF 90 88 9A 8D 82 FF EF FF

Same as the .g3p header, which means that the byte doesn't directly translate to a specific filetype. It might relate to how the OS should run it, though. The .g3b format is basically a series of images one after another.

That's basically what I was saying  

I'm currently working with the KPIT GNU tools. You have to register to use them, but they're free.

There are 15 file types:

.g1m .g1m .g2m .g3m .g1r .g2r Data files .g1e .g2e .g3e E-activity files .g3a Add-ins .g3l Add-ins and menus .g3p Picture files .g3b Animation files .bmp Screenshot picture file .txt Text file .csv CSV file (Matrix, list, or spreadsheet)