RCL-57 now available at the App Store

[pauln]

Good question. This was my first time writing a hardware based emulator so it wasn't obvious for me either.

How To Write a Computer Emulator by Marat Fayzullin gives a good overview of the general process.

For RCL-57, I used Patent US4125901A which describes carefully the instruction set. Here is my translation of this patent into C code: https://github.com/n3times/rcl57/blob/ma...ine/ti57.c.

This should be enough to write an accurate but barebones emulator.

In my opinion, an emulator is much more fun to use if it gives information about the state of the calculator. For example the list of steps in readable form, the trigonometric mode, the log of operations etc. To do this one needs to understand the internal state of the calculator. The TI-57 memory map by Claus Buchholz covers some of it and is a good starting point. See https://github.com/n3times/rcl57/blob/ma.../state57.c for my own code and more of the internal state deciphered.

What I have described until now is what I call the engine. For RCL-57, it is standard C code that can be easily packaged into a library and used to write a TI-57 emulator for most common platforms (iOS, Android, ...).