OSDev.org

This is a toy, monotasking, self-hosted operating system for the Arduino Due (ARM-v7M microcontroller, 96KB RAM, 512KB flash), in less than 3300 lines, for educational purposes(*). It is made of:
- a boot loader (~70 lines)
- a monolithic kernel with 3 drivers, a file system, and 10 system calls (~1080 lines)
- a small, statically typed, C-like compiler with only unsigned 32-bit ints and struct pointers (~1330 lines)
- a text editor (~220 lines), a shell (~230 lines), and 5 commands (ls, cp, rm, etc -- ~200 lines)

Links:
- book: https://ebruneton.github.io/toypc/toypc.pdf
- companion website: https://ebruneton.github.io/toypc/
- emulator: https://ebruneton.github.io/toypc/emula ... /final.txt
- source code: https://ebruneton.github.io/toypc/toys.zip

(*) the goal is not to teach how to write an OS. Instead, it is to introduce this topic via a practical example.

It's good to see OSs for embedded hardware, I'm thinking of going that way myself. I sketched out a plan for an OS on a board with just 16KB RAM the other day, but that might be too small. :) The planning centered around using a Forth block scheme for virtual memory, but I doubt SD-card write speeds are fast enough for my taste.

It's interesting to see Toys clear the screen before running each command. I was just planning a script window in place of the command line for my larger OS, trying to decide whether or not it should clear after every run.