Reflections on an Operating System Design
The main features of a general purpose multiaccess
operating system developed for the CDC 6400 
at Berkeley are presented, and its good and bad points are
discussed as they appear in retrospect.  Distinctive 
features of the design were the use of capabilities
for protection, and the organization of the system 
into a sequence of layers, each building on the facilities
provided by earlier ones and protecting itself 
from the malfunctions of later ones. There were serious
problems in maintaining the protection between 
layers when levels were added to the memory hierarchy;
these problems are discussed and a new solution 
is described.
CACM May, 1976
Lampson, B. W.
Sturgis, H. E.
