Well, the basic procedure would involve:
1. creating a casio basic file containing the characters you want (and preferably some descriptive text so you can tell which is which)
2. uploading this file to the computer in a binary form
3. hex editing it to find the character codes for the special symbols
4. editing textreader's font.bmp file and adding your character(s) at the end of it on the right
5. running the (visual basic 6 if you need runtimes) conversion utility to create the packed font bitmap from the .bmp
6. editing minifont.asm to add the characters to the position/size lookup table (this can be tricky because as it is, the table assumes a continuous block of characters supported, so you would either have to add a lot of zeros to make the characters you add line up, or modify the assembly code to change the lookup method. Note that the position corresponds to the graphic column in font.bmp, so there can be some funky compression done in the font.bmp by overlaping characters, as I've done
)
7. reassembling textreader.asm
If you give me a modified font.bmp file and tell me what characters have which ascii codes (or I suppose, I could look up the character codes if you tell me how to get to each character in the casio editor), I'd be happy to modify the assembly code and put together a new version for you. Note that if any of these characters have prefix characters, they won't be supported. Both minifont and textreader are clueless when it comes to handling these properly.
If the needed character is already part of the supported ascii codes (such as + or -, maybe others), I added a translation table in minifont.asm to convert these casio codes to the real ascii codes to keep minifont.asm a little cleaner from having to support duplicate characters. If you add too many of these, it will slow down the viewer a bit though.
Anyway, that's the overview
