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From: 54394gt@hocda.UUCP (G.TOMASEVICH)
Newsgroups: net.unix-wizards
Subject: Levels of UNIX, an opinion, a question
Message-ID: <356@hocda.UUCP>
Date: Mon, 6-Feb-84 15:54:36 EST
Article-I.D.: hocda.356
Posted: Mon Feb  6 15:54:36 1984
Date-Received: Thu, 9-Feb-84 07:36:46 EST
Organization: Bell Labs, Holmdel
Lines: 10

In the paging-in-somewhere discussion someone asked if UNIX has any levels
besides kernel and user.  I believe not; it originated on a PDP-11, probably
one without supervisor level (I'm not sure).  Now the only use of supervisor
mode on the PDP-11 is to accommodate a kernel that outgrew the kernel-mode
address space.  At that point, UNIX already started becoming a pig, and
now look where it is!  You need a VAX, huge disks, etc. to run everything.
The shell was outside the kernel because of the address space limit.
The question: where should one draw the line on putting shell, terminal
features, editor, etc when the machine has a huge address space?  This leads
to Rob Pike's discussion.