From: Operating systems teaching

- Minix, from Amsterdam's Vrije Universiteit, was developed by Andy
  Tanenbaum <ast@cs.vu.nl>, and is a mostly-Unix lookalike based on
  a message-passing microkernel-similar architecture.  The system is
  used in Tanenbaum's `Modern Operating Systems' and its predecessor,
  `Operating Systems: Design and Implementation'.  See the Minix
  Information Sheet, posted regularly to comp.os.minix, for ordering
  information; Minix is copyrighted and is not in the public domain,
  but is available from <URL:ftp://ftp.cs.vu.nl/pub/minix>.  For
  further information, see Andy's Web page at
  <URL:http://www.cs.vu.nl/~ast>.

- NachOS is an instructional OS developed at Berkeley by Tom Anderson
  <tea@cs.berkeley.edu>, Wayne Christopher, Stephen Procter (and
  others?).  It currently runs on DEC MIPS and Sun SPARC workstations,
  HP PA-RISC, and 386BSD machines.  The NachOS system, along with
  sample assignments and an overview paper which was presented at
  Usenix, is available via anonymous ftp from
  <URL:ftp://ftp.cs.berkeley.edu/ucb/nachos>.

- OSP (current version is 1.7) is an operating systems simulator,
  available via ftp from <URL:ftp://sblapis1.cs.sunysb.edu>, with
  username ospftp, and password as in the instructor's guide.  Used in
  `OSP---an Environment for Operating Systems', Michael Kifer, Scott
  Smolka, Addison-Wesley.

- RCOS (Ron Chernich's Operating System) is a simulated operating
  system that is intended to demonstrate graphically the concepts
  behind operating systems.  Students can investigate and modify the
  algorithms it uses, and write programs in a Pascal-like language
  (extended with semaphores and shared memory) which it will execute.
  RCOS has a windowing interface, and currently runs under MS-DOS; an
  alpha-quality Unix/X11 port is also available.  For further details,
  check out the Web page at
  <URL:http://cq-pan.cqu.edu.au/david-jones/projects/rcos>.

- SunOS Minix consists of a set of patches for Minix which allows the
  Minix system to run in a single monolithic Unix process on top of
  SunOS 4.x on Sun 3 and Sun 4 machines.  SunOS Minix is produced by
  applying a set of patches to Mac Minix 1.5 (both 1.5.10.0 and
  1.5.10.1 can be used) or PC Minix 1.5.  Also, Atari Minix has been
  used as the base version by at least one person.  The latest version
  (2.0) includes a preliminary attempt at a port to Solaris 2.x.
  SunOS Minix is available via anonymous ftp from
  <URL:ftp://csc.canterbury.ac.nz/UNIX/>.

- VSTa is not intended as an instructional operating system, but it is
  certainly small and concise enough to be tractable, and the code is
  clean and provides modern microkernel features.  See part 2 of the
  FAQ for further details.

- Xinu was developed at Purdue by Doug Comer and some others.  It was
  designed to be small and layered, so that the code is succinct and
  easily understandable.  It is intended for education, and is a
  `conventional' operating system.  Xinu runs on the IBM PC, Sun-3,
  SPARC, LSI, MIPS, Macintosh, and VAX architectures.  The system is
  used in Comer's `Operating System Design: the Xinu Approach'.
  See <URL:http://www.cs.purdue.edu/homes/dec/xlicense.html> for
  licensing information.