From: Gail Rahn (gail_at_screaminggeek.com)
Date: Wed Jan 07 2004 - 15:54:05 PST
The Ritchie and Thompson UNIX paper is an introduction of an early version
of UNIX. The paper describes the hardware and software environments in which
UNIX runs, internals of the file system structure and addressing, functions
in C that interact with devices and files, facilities and APIs for
interprocess communication and synchronization and user interaction with the
system.
Aside from the historical oddities in the paper (only $40,000 for hardware
to run UNIX! UNIX occupies 42k of memory!), I especially noticed the
operating systems advancements made in the time between THE and UNIX. In
contract with THE, which was written for dedicated hardware, UNIX is
somewhat portable and "includes a large number of device drivers". UNIX also
implements a shell - more advanced than THE's "message interpreter" and
capable of searching and running installed programs. UNIX also introduces
concepts of file management, protection and addressing.
A major improvement since THE is also that UNIX cares as much about managing
files as it does processes. Where THE goals of THE seemed singlemindedly to
facilitate multiprogramming, UNIX accomplishes that while also considering
the problem of managing persistent storage of arbitrary files. This
operating system considers the file system to be permanent storage - and
considers the file system to be an extremely important OS component.
On the process front, UNIX advances the concept of process management by
reducing the atomic unit of execution from the program (as in THE) to the
thread.
I can't believe I'm about to write this, but in contrast to a system like
THE, UNIX considers and accomodates the (trained) user. A computer operator,
using UNIX as described in this paper, can provide credentials, access
private and shared directories, protect files using bitmask-based
permissions, manage files by creating/moving/renaming/deleting, access other
file systems by manually mount and unmount removable storage. A user can
even play games in UNIX.
-- Gail.
grahn_at_cs.washington.edu
-------------
Gail Rahn
gail_at_screaminggeek.com
206.719.5563
Screaming Geek Software
www.screaminggeek.com
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