If you’ve been looking at operating systems for the TI-84+, chances are you’ve come across KnightOS. It’s well developed and has plenty of Unix-like features such as filesystems and tasks, and even a C compiler. But maybe that’s not what you want. You want an minimal operating system that allows you to extend it in any way you wish, bonus points if you don’t need to know Z80 assembly to do so.
zkeme80 is that operating system, a minimal core with a mostly ANS standard conforming Forth interpreter/compiler. From words covering sprites and graphics, to text and memory access, everything you need to make the next hit Snake clone or RPN-based layer is already there. zkeme80 lowers the barrier of entry for customizing an operating system and enable rapid development cycles. Below the Forth layer, you’ll find two lowest level and highest level languages, Z80 assembly and Scheme. The best assembler is an extensible one, where writing macros should be a joy, not a pain, and Scheme has that macro system.
I wish I still had the TI-83 I used back in high school. A friend and I bought a communication cable for our TI-83s so that we could play multiplayer Bomberman during classes. Fun times.