Z80man, try editing the data around 0970F0 and see if that makes any difference. Of course, that could very well be app storage space, but...

Hm, I don't see anything else in the header that could be an icon except for the data between 4000 and 6DFD.

I screwed up on the character set. I don't know where it is, but what I posted is almost certainly not it. That code repeats itself several times later in the OS.

Okay in the header there are actually two different icons. One for when the cursor is over the icon and one when it isn't. In my opinion I think Casio could have coded this differently in a way that you only provide one image in the code instead of two considering that the cursor is the same for all apps, but maybe this way is faster. The location for the image when the cursor is not over the icon is at 0x1000 and the one for when the cursor is over the icon is at 0x4000. 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 only other data in the header is a small amount of text at the beginning and the file name at 0x0EBC. This text at the beginning for the conversion app is  "ª¬½¯.ˆš.ÓÿþÿþÿÂþÿÿŽ.K.É..........'Ød.............ø..............Conversion....................qü@CONV......Conversion..............Conversiæ.n.............Konvert.................Conversion..............Conversæ.o..............µ¥Î»»»Ëã................Conversion..............Conversion...................01.00.0000..2010.0813.0920......". To make things more difficult the geometry app has a bunch of $0 and $7 code in a random order after the initial text. For example a segment of it is "77 77 77 77 77 77 77 77 70 00 00 00 00 07 77 77". The majority of all of the data is 7's. Does anybody have any ideas of what this could be? Not all the apps have this though.

No, he's modify the Casio equivalent of an Application and sending it to his calc. The OS itself has to wait for a bit before we're ready for it.

@z80: I'm not entirely sure about the other stuff, but the text has to do with language localization. On some of the other add-ins, you may notice that the text is actually the title in other languages. You'll notice similar stuff was done with much of the internal text as well.

Also, it would appear from manufacturer documentation that if your program has the proper permissions, you can multiply the clock requency by up to six times, giving a processor ceiling of 174 MHz. The downside is that you need to wait ~100 ms after switching the frequency to start processing again.

source

I suspect they've hidden a checksum or security bytes in their header. Let me take a look.

I think my suspicions were right.

Z80, what happens if you change only things that are FF to 00 and vice versa?