[Simh] What is CDC OS?

[Will Senn]

Hi,

I'm reading a book (among many such books) that is entitled, "A Primer 
on PASCAL," by Richard Conway, David Gries, and E. C. Zimmerman, written 
in 1976 with a Foreward by Niklaus Wirth. The book has a lot of PASCAL 
examples that run just fine on my PDP-11/70 with RT-11 or RSX-11, or... 
you get the idea. However, the book has some programs that claim to take 
advantage of the CDC OS and utilize a card reader. The author refers to 
the operating system as "The CDC OS" as if it were singular and obvious, 
but doesn't speak of hardware beyond the card reader. I looked and found 
references to Control Data Corporation's COS, SCOPE, MACE, KRONOS,  and 
NOS, but have no idea if these are "The CDC OS"...

Does anyone know what "The CDC OS" would refer to and what hardware it 
would run on (hopefully simulated).

Regards,

Will