History of OSs? - test-drb@ccmp.vtda.org

17 Mar 1998

...
 The dos geneology is roughly...

DEC PDP-8 OS/8 (pip, stat, dir)--> RT-11/RSTS/RSX11-->
...
                             CPM-80-->
                              CPM86-->
                                 dos-1.0-->

The VAX OS line up VMS is off the RSX11 part fo the PDP-11 tree.
...

DOS was a translation of 8080 CPM-80 to 8086 by seattle computer. Unix
...
 has been an influence but largely not that great.

UNIX has it's own tree and there are to say the least many flavors some
...
 of which even resemble each other.
Allison 
To add in a bit more....
CP/M comes directly from RT-11 and the RSTS tree.  Even the PIP
command (peripheral interchance program) was very similar to the
RT-11 version of PIP.  CP/M had a more sophisticated file system
than RT-11, but less sophisticated device drivers.

VMS was not the first virtual memory OS that DEC wrote.
TOPS-20, for the PDP-20 (that was a PDP-10 with virtual memory)
was the first virtual system.  TOPS-20 was not the same as
TOPS-10, even the system calls were invoked a different way.
(My first real systems programming job was on a 20/40, a joy to
work on, tho slow by modern standards).
        Jack Peacock