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16 FE FF FE B9 57 9F ; picture plot
16 FE FF F4 75 57 9F ; geometry
C2 FE FF FF 8E 03 4B ; conversion

I figured out part of the copy protection. First of the 2nd and 3rd bytes appear to always be FE anf FF, but thats pretty obvious. More interesting was if you subtract from the picture app's 4th, 5th, and 6th bytes by the geometry app's 4th, 5th and 6th you get the same difference of their file size not including the header. You will notice though that for the 4th, 5th and 6th that the conversion app has the greatest number and the geometry the smallest which may seem strange at first considering that the conversion app is the smallest and he geometry app is the smallest. Checking it over again I noticed that the bytes were written in inverse binary. As in the 1's became 0's and the 0's became 1's. So these bytes are just the file size written in inverse.

44. Force them to use their calc for math only

Btw, I don't quite understand how basic lacks integers?  Isn't that essential for a calc?

All math in basic is done with floating point variables which are much slower and take up more space

What I felt what was missing from basic were
1. grayscale support
2. the last row and column of the screen
3. turn off the run indicator (It's way to annoying)
4. integers
5. sound
6. turning screen on and off (I used this to make an asm program that made my teachers think they had deleted my ram)
7. pixel lines, not graph screen lines
8. crash the calc ( when wrong password is entered)
9. efficient memory storage
10. capability to run programs that require speed

Hi I'm Z80man. I'm currently a sophmore in high school. Last year I got my first graphing calculator, a Ti-84+ SE. Within a few weeks I was making my first basic programs. As I got better I made more advanced programs. Eventually I became frustruated with the slow speed and lack of capability of basic. Thats when I was introduced to asm programming. I'm also fluent in the C/C++ langaunge too. This year for Christmas I got the Casio Prizm. As of now I'm trying to decode the header for apps. Other news about me is that I'm am an avid runner competing on both my school's cross country and track teams.

There needs to be a site like wikiti.brandonw.net/ but for casio calcs

It appears more than one checksum is used. After running a checksum-32 algorithim on the conversion app I got 0027DB. At 0x0020 in the code appears 0027D864. On the Geometry app the algorithim got a result of 014DD578 and at 0x0020 was 014DD1DC. So the checksum doesn't include the entire code. I can't figure out what part is left out though. For the geometry app the first part of the header is AA AC BD AF 90 88 9A 8D D3 FF FE FF FE FF 16 FE FF F4 75 57 9F 00 49 12 00 00 00 00 00 00 00 00 04 1D D1 DC 01 01 00 00 00 00 00 00 00 00 00 0B 1A A4 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Quote from: z80man on December 27, 2010, 04:31:55 am

Quote from: kucalc on December 27, 2010, 04:17:30 am

Quote from: z80man on December 27, 2010, 03:23:09 am

After changing some of the data you can see a change in the icon, but then the app becomes unrunnable. Any ideas why would be helpful.

The first 2 bytes in the headers are 0xAA and 0xAC, right? On the fx-9860, to disable the checksum you would change the first byte (0xAA) to 0xAC. Try and see if that works.

I tried changing the first byte from $AA to $AC, but the app is still not running.

What happens if the first byte of an unmodified app is changed to 0xAC?

ah ha!! I figured it out!!! The OS uses a modular sum checksum. So as long as I keep the sum of all the bytes added together the app will run. All we need to do now is find out where this sum is located that way we can start modifying some code. Also if you change the first byte to $AC the app does not run.