From: Sellakumaran Kanagarathnam (sellak_at_windows.microsoft.com)
Date: Wed Jan 07 2004 - 12:52:04 PST
The UNIX Time-Sharing System - Dennis M.Ritchie and Ken Thompson, Bell
Laboratories
This paper gives a brief history of the UNIX system, hardware, explains
the idea behind building the operating system, design considerations,
influences on the operating system and also it gives very decent
information on file systems, processes and images and the shell. The
authors end with some statistics on the usage, although it is not very
clear where these statistics are collected.
The UNIX system has a fairly uniform system for files, directories,
devices and removable storage. The protection mechanism is simple and
effective. However I don't think we can give selective access for a
file to a set of users with this mechanism. The set-user bit is very
useful, although if improperly used, it will be a security issue. The
authors then explain some actual I/O calls and go on to describe the
implementation of the file system. When explaining the file system,
the authors are very informative and explain some basic concepts like
i-node in simple easy to understand text.
They go on and explain processes and images which is again very
informative (user-core part of the image and so on).
Then the authors give a detailed explanation of the shell which is very
good, but I was inclined to think that some of the information like
command examples in this section could have been skipped for this paper
(the section made me feel that it was a small user guide to shell). But
I guess all this detail is present because some of the important
features like I/O redirection and filters are implemented or used
primarily in the shell.
It is surprising to note that the initial version of UNIX was a personal
effort considering the features present.
Overall I think that this paper gives a good informative introduction to
UNIX.
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