classic operating systems

<question: Is there any classic operating system known for which the <complete source code is available ? Well if you took the time to look and read... This is a non exhaustive list of just a few. CPM (8080, z80, 8086, 68000) This also includes all of the CP/M clones such as P2dos, Suprbdos, Zrdos, Zsdos. These can be found at various FTP sites on the net. Uzi Unix (z80, z180, z280) Can be fount as www.psyber.com/~TCJ and also several other versions at FTP sites. Minix (808x, 80x86 and others) the book Operating System Design and Implmentation ISBN 0-13-6386677-6 By Tanenbaum and Woodhull. Also the sources and executables are on the net. Pretty good simplified unix like OS that is source available for teaching and other student/research use. Classic Unix is available with a lowcost license (versions include V5, 6, 7 and a whole load more. RTS-8, OS/8 (also OS278) for PDP-8 family are at various places on the net. This OS is good for illustrating the close relationship of hardware to software. Allison