Not Another Completely Heuristic Operating System: teaching OS coded in C++ subset, developed at UC Berkeley for OS and Systems Programming classes; now used worldwide. Descriptions, FAQ, port and bug lists, assignments, downloads. [Open Source]

Academic Operating System, goals: to expose students to more modern ideas than older OSs, to basic OS mechanisms, to OS and language design and prototyping; old version, ideas for new microkernel version.

Teachable Operating System: tiny multithreaded messaging microkernel, in ANSI C; protected threads, memory managed, and thread/process control. From undergraduate course on concurrency, device programming, OS concepts. Descriptions, documents, theses,...

Goal: provide all students need to learn OS concepts: basic functions, kernel internals, microkernel architecture, to advanced distributed concepts, and to develop theirs, step by step.

Kid Operating System. Modular (run-time dynamic linking), preemptive multitasking, to have SVR4-like VM. Begun 1998 by young programmers, most of them students. Goal: not obtaining OS, but learning OS internals and functioning of x86 processors. Downl...

Tool to learn: how simple OSs work, OS development, x86 assembly language; simple code, ample documentation, often add new features on request. Open source.

Scott Billingsley's OS: realtime for DSP and amateur radio, one user/application, 16-bit real mode, for i386+, FAT 12/16; no TSRs, library of routines to program into apps, minimal kernel support (minimize interrupts), written in NASM assembly and Sph...

Port, extension of instructional OS, now stand-alone, protected mode, multithreaded, compiles in FreeBSD to run on i486+, can be relinked without recompile. Descriptions, report (HTML, PDF, PS), download. [Open Source]