Hi there! I recently picked up an fx-CG50 for a maths course at my college and I'm planning to gradually build out my own CAS for it as a bit of fun and to teach myself a bit more about solving different kinds of equations.

These forums have been really useful already, but there are still some questions I haven't found answers to yet, so here I am

At the moment, I'm looking at how to implement the input, and ideally I'd be able to draw the equations in a similar manner to Run-Matrix (with exponents justified correctly e.t.c.). Do we have any way to reuse that code, or the font it uses?

Thanks a ton!

This I believe will help https://prizm.cemetech.net/index.php?title=Category:Syscalls:Text_and_expression_editing

To figure out how whole expression are formed (subscript/superscript/nesting etc) look in a hex editor how expressions are saved in eactivity files or perhaps at a dump of main memory if you can find where run-matrix saves its history.

As far as I know the code for expression tree handling and printing on the OS is either "hidden" and/or not reverse-engineered.

If you do end up writing your own, you might find some ideas of value in this TeX library I wrote a while back. I don't think it would be nearly powerful enough for a CAS and it doesn't look too great on the CG-50, but the code/data structure might be of interest to you.

Thanks for the links The system call reference looks great and I'm definitely going to draw from your Tex library Lephe (btw your comments are brilliant! just the right amount of detail).

The eActivity format is a good start too. I'm pretty sure it's storing the math in a tree with length-prefixed nodes. The contents are mostly plaintext (the numbers are stored in ASCII 😀) with some magic numbers for each of the operators.
The header's going to be harder to make sense of... maybe I'll find something about it in the forum history.

I'll take a stab at reversing some of eActivity to see which APIs it's using. How should I get that memory dump? And what's the best way to disassemble the addins atm?

Good luck! For e-activies there are a couple documents which give information. You might not get the tree structure but at least you should be able to parse files at a high-level. You have SimLo's reference (as usual). I also know of one unfinished library which implemented different formats and parts of the eact format; see around here, maybe this can help. ^^

Awesome, cheers! At least I was on the right lines with the header, I should've checked the reference haha. It's a relief I don't have to worry about keeping track of more offsets.

To read memory you can use Simon’s Insight add-in - when I used it on cg20 model in the past you could navigate second screen (F6) and used F2 MCS view to show main memory tree etc but on my cg50 it doesn’t seem to function same way - could be just my os or addin version - but you should be able to dump entire memory still and find the relevant areas.