Softpanorama (slightly skeptical) Open Source Software Educational Society

May the source be with you, but remember the KISS principle ;-)

Slightly Skeptical Unix History with Some Emphasis on Scripting

The book Life with Unix by Don Libes and Sandy Ressler is fascinating reading for anyone interested in Unix in general and scripting history in particular. It covers a lot of the history, interactions, etc. Much in the present section is summarized from this book. Some interesting info is in UNIX FAQ.

As most of the readers know Unix history goes back to 1969 and the famous "little-used PDP-7 in a corner" on which Ken Thompson, Dennis Ritchie (the R in K&R), and others started work on what was to become Unix.

But what is less known and appreciated is the fact that Ken Thompson was also the author of the first UNIX shell and that concepts of this shell greatly influenced the subsequent work of John Mashey and Stephen Bourne. Influenced to the extent that John Mashey actually objected to calling his shell Mashey shell considering it as a direct extension of Thompson shell.

The name "Unix" was intended as a pun on Multics (and was written "Unics" at first, for UNiplexed Information and Computing System). As Ch 9 of the Netizens Netbook  (   On the Early History and Impact of Unix Tools to Build the Tools for a New Millenium) aptly stated:

When AT&T made the decision to pull out of the Multics collaboration, they took the research operating system off their GE 645  computer and put up the GECOS operating system. Though GECOS was adequate  for applications, it was "nowhere near as satisfactory if you were trying  to do things that were technically difficult and imperfectly defined,"  explained Vyssotsky, "which is the main task of research."(23)

 For the pioneering work of Bell Labs research programmers like Ken Thompson and the research purposes of the Labs, an operating system more  like what Multics had promised was needed. Along with the advantages of  immediate feedback which time-sharing provided, the Bell Labs researchers  wanted to continue the ability to work collaboratively which time-sharing  had made possible.

"What we wanted to preserve," one of the creators of Unix, Dennis  Ritchie writes, "was not just a good programming environment in which to  do programming, but a system around which a fellowship could form. We knew from experience that the essence of communal computing, as supplied by remote-access, time-shared machines, is not just to type programs into a terminal instead of a keypunch, but to encourage close  communication."(24)

Ritchie describes how an informal group led by Thompson had begun  investigating alternatives to Multics before the GE-645 Multics machine  had been removed from the Labs.(25) Thompson and Ritchie presented Bell Labs with proposals to buy them a computer so they could build their own interactive, time-sharing operating system. Their proposals weren't acted on. Eventually, Thompson found a little used PDP-7 computer. According to Vyssotsky, the orphaned PDP-7 computer was a machine, "more in the class of a Commodore 64 than the class of a PC-AT."(26)

For the first 10 years, Unix development was essentially confined to Bell Labs and most scripting related work was also done in NJ. The initial versions of Unix were labeled "Version n" or "Nth Edition" (of the manuals) and some milestones in shell history are directly related to particular Unix releases.  Major early Unix implementation were for DEC's PDP-11 (16 bits) which was so tiny by today's hardware standards (typical configuration were limited to 128K memory, 2.4M disc, 64K per-process limit (inc the kernel)) and similar configurations can be found only in palmtop computers and top electronic watches ;-). The fact that they managed to created pretty powerful shells for such a computer is nothing but simply amazing and attests tremendous ingenuity of early creators of Unix extremely well.

• 1971 V1: 1st Unix version written in assembler on a PDP-11/20. Included file system, fork(), roff, ed. Was used as a text processing tool for preparation of patents.
   
• 1972 V3: Pipe() appeared first in V3!
   
• 1973 V4: Unix was rewritten in C.
   
• 1974 V5 The UNIX Time-Sharing System is published in CACM by Ken Thompson and Dennis Ritchie. It is a revision of the 1973 paper. Fifth edition was made freely available to universities for educational purposes. University of California at Berkeley (UCB) gets Version 4 of UNIX.  In January 1974, a Version 4 tape was delivered and Unix was installed in Berkeley by graduate student Keith Standiford.  Berkeley begins making major enhancements to UNIX and sets the stage for becoming a major distribution center for their version of UNIX. The Elements of Programming Style by Kernighan and Plauger is published.
   
• 1975
  • V6: First version of Unix widely available outside Bell Labs. Thompson begins one year sabbatical at Berkeley bringing V6 with him. AT&T officially begins licensing UNIX to universities. Due to its portability and flexibility, UNIX Version 6 (V6) became the minicomputer OS of choice for universities in 1975. In the fall of 1975 were two graduate students, Bill Joy and Chuck Haley start working on Unix. J. Lions published his famous "A commentary on the Unix Operating System" based on V6.
     
  • PWB Unix got Mashey shell -- the first powerful shell for Unix that was close to a scripting language.  As John Mashey recollected:

    The "PWB Shell" first appeared in mid-1975. It derived from a set of requirements and suggestions from me in early 1975 in trying to do serious shell programming. In mid-1975, the shell acquired variables, including 3 that were derived from per-process data. This is where the idea of more generalised path- searching came in. Some of the existing support commands were beefed up, including if/else/endif. Most of this work was done by Alan Glasser or Dick Haight. I ended up taking this over, doing performance analysis, moving most of the control structure commands into the shell, adding switch,, while, etc. etc.  By this time there was serious shell programming in massive amounts. This had mostly stabilised by early/mid 1976, although a few more features were added in early 1977. For various reasons this came to be called the "Mashey shell", a term I universally abhorred, since it was fundamentally still a Thompson shell with selected additions and tunings by various of us, constrained to be mostly upward compatible, leading to some things that I found less than esthetic. Even less than esthetic was the title of a later internal Bell Labs course: "Bourne Shell Programming for Mashey Shell Programmers". See [2] and [3].

    Bell Labs Piscataway used the PWB shell quite heavily for its scripting needs in the mid-1970s and that probably was the first time a scripting language was widely used outside research. Rephrasing John R. Mashey  quote "UNIX is a lever for the intellect"  we can say that "Scripting is a level for the intellect". thirty years later we are taking scripting for granted, but it was pretty amazing breakthrough made on a PDP 11 of those days with typical configuration 128K memory, 2.4M disc, 64K per-process limit (inc the kernel). Unix on PDP 11 was a tight squeeze, and utilities like "sh" had to be extremely tightly coded. Mashey shell was also pretty fast (faster then Bourne shell that replaced it later).
     
• 1976. John R. Mashey publishes the paper "Using a Command Language as a High-Level
  Programming Language", Proc. 2nd Int. Conf on Software Engineering, IEEE (Oct 13-15, 1976), 169-176. -- the first paper about scripting as a very high level programming language.
   
• 1977. The new scripting language awk is designed by Alfred V. Aho, Peter J. Weinberger, and Brian W. Kernighan. It was designed to be used with shell, but in essence it needed to be integrated into shell, which was done later in Perl and ksh93. 
• 1978
  • A Borne shell by Stephen Bourne, simply known as the 'sh', is released. It became the most popular Unix shell for the next two decades.
  • Awk was first described in Software Practice and Experience in July, 1978, and first distributed with Seventh Edition UNIX.  That was the next major step in scripting languages development in Unix after Mashey shell.
  • 1978 Bill Joy produces 2BSD, the "Berkeley Software Distribution", that contains C-shell (2BSD was a set of applications that ran on 6th Edition UNIX, and was not a kernel nor a set of kernel patches). It was implemented as a standalone interpreter. Csh was a big improvement over the original sh in many respects; it had more built-in commands, a different and friendlier syntax with better  flow control constructs and an arithmetic facility and most importantly of all command history.  But its primary contribution was a better command interface. Among key ideas here were the ideas of a history list and an in-line editing. Combined they produced a kind of pseudo-GUI environment that saved users a lot of typing. Naturally, csh took off quickly. A full distribution of the 2BSD tape is available at http://www.tuhs.org/Archive/PDP-11/Distributions/ucb/
  • Famous  Steve Bourne paper, "An Introduction to the UNIX Shell"  was published (BSTJ  57, No 6, Part 2 (Jul-Aug 1978), 2797-2822)
  • Steve Johnson complete first port of UNIX to an Interdata 8/32, the first non-DEC computer to run UNIX. Note that this is nearly ten years after running only on DEC equipment.  UNIX is ported to a DEC VAX, but not by Thompson and Ritchie, since they had become disenchanted by DEC and its unwillingness to support UNIX. DEC's initial refusal to support UNIX must be one of the all time great blunders of the computer industry.
  • The C Programming Language by Kernighan and Ritchie is published and served as the standard for the C language for over a decade, until the ANSI C standard appeared in December 1989.
     
• 1979
  • V7: It included full K&R C, uucp, Bourne shell and awk. V7 was ported to the VAX as 32V. The V7 kernel was a mere 40KB! Here (for reference) are the system calls of V7:

      _exit, access, acct, alarm, brk, chdir, chmod, chown,
      chroot, close, creat, dup, dup2, exec*, exit, fork, fstat,
      ftime, getegid, geteuid, getgid, getpid, getuid, gtty,
      indir, ioctl, kill, link, lock, lseek, mknod, mount,
      mpxcall, nice, open, pause, phys, pipe, pkoff, pkon,
      profil, ptrace, read, sbrk, setgid, setuid, signal, stat,
      stime, stty, sync, tell, time, times, umask, umount,
      unlink, utime, wait, write.

  • T. A. Dolotta and  John Mashey presented a talk and published a paper "Using a Command Language as the Primary Programming Tool" at IFIP Working Conference on Command Languages, Sept 10-14, 1979.
     
• 1981 C-shell was extended into tcsh, which for a long time became the most popular interactive shell. It introduced the idea of command completion.
   
• 1982. David Korn created ksh -- a dominant shell in commercial Unixes till this days.
   
• 1987. The first version of Perl was developed by Larry Wall  at  the end of the year. See excellent  PerlTimeline for more information. Perl was an attempt to combine the capabilities of the shell and awk into a single language.  Because Perl is freely available and performs better than combined shell and awk, Perl rapidly acquired a large user community, primarily at universities. Here is the description from Perl manpage:

  NAME
  perl | Practical Extraction and Report Language
  
  SYNOPSIS
      perl [options] filename args
  
  DESCRIPTION
       Perl is a interpreted language optimized for scanning  arbi
       trary  text  files,  extracting  information from those text
       files, and printing reports based on that information.  It's
       also  a good language for many system management tasks.  The
       language is intended to be practical  (easy  to  use,  effi-
       cient,  complete)  rather  than  beautiful  (tiny,  elegant,
       minimal).  It combines (in  the  author's  opinion,  anyway)
       some  of the best features of C, sed, awk, and sh, so people
       familiar with those languages should have little  difficulty
       with  it.  (Language historians will also note some vestiges
       of csh, Pascal, and  even  BASIC|PLUS.)   Expression  syntax
       corresponds  quite  closely  to C expression syntax.  If you
       have a problem that would ordinarily use sed or awk  or  sh,
       but  it exceeds their capabilities or must run a little fas-
       ter, and you don't want to write the silly thing in C,  then
       perl  may  be  for  you.  There are also translators to turn
       your sed and awk scripts  into  perl  scripts.   OK,  enough
       hype.

• 1988 John K. Ousterhout developed TCL, the first embeddable scripting language for Unix. 

  I began work on Tk in late 1988, but it was a part-time project, so it took about two years before there was enough functionality for Tk to be useful.
  ... By 1989 I was using Tcl in a couple of projects, and I believe that I gave a talk on Tcl during the Berkeley Industrial Liaison Conference, where several hundred people from industry came to Berkeley to hear about research in our department. I believe that this led to invitations to give talks on Tcl at a few interested companies, and that some of the people at those talks asked if they could have copies of Tcl. In any case, I gave away a few copies of Tcl to early adopters in 1989.
  
  In 1994 John Ousterhout joined Sun. Unfortunately Sun blowed away a chance to make TCL a standard Unix macro language the way REXX was in OS/2.

• 1989.
  • As part of the GNU project Chet Ramey developed the Bourne-Again Shell, bash. Initially was rather weak but later became a prominent shell due to Linux.
  • Z Shell was created by Paul Falstad in Princeton University, NJ were he was a student. This was the first of "super-shells" a shell designed for interactive use that doubles as a decent scripting language. Many of the useful features of bash, ksh, and tcsh were incorporated into zsh; many original features were added. Later David Korn created ksh93 with a similar agenda.
     
• 1990 
  • Python was created by Guido van Rossum at CWI in Amsterdam.
  • Don Libes of the National Institute of Standards and Technology created Expect.  He made Expect freely available after presenting his paper in the summer of 1990, and it became an instant hit among system administrators. Expect was not only the first widely distributed Tcl application, but for many years it was the most popular scripting application in Unix universe. Many of the early Tcl users learned about it by using Expect.
  • John Ousterhout presented a paper on Tcl at the USENIX Conference n January.
     
• 1991. Perl 4.000 is released and includes an artistic license as well as the GPL.
   
• 1993. David Korn released ksh93, an attempt to backport some Perl features into shell framework. Here is a partial list of ksh93 features:
  • Associative arrays - ksh88 already supports indexed arrays.
  • Floating point arithmetic + math library functions.
  • Arithmetic for command similar to C and awk.
  • Complete ANSI C printf formatting with extensions.
  • Run time linking of libraries and builtins.
  • A number of additional substring operations such as offset length.
  • Full extended regular expression matching capabilities
  • Compound variables which can be used to represent data aggregates.
  • Name references for passing aggregate variables by name.
  • Active variables. Users can trap variable assignment and references by associating intercept functions of the form name.get and name.set.
  • Ability to make socket connections to servers by name.
  • read with timeouts.
  • Conformance to POSIX 1003.2.
  • Command completion and variable completion, ksh93 only had file name completion.
  • A key binding mechanism that allows users to bind keys to new editing functions.
     
• 1994. Perl 5.000 is unveiled.

There several questions that are usually swiped under the carpet when writing about Unix history

• The actual level of influence of Multics and CTSS. To what extent Unix was a copycat OS and to what it was a new and unique amalgam of preexisting best features in earlier OSes taking them to a new level.

• The role of Unix in promoting of scripting. Unix proved to be the fertile ground for scripting development and essentially pioneered scripting as it the first environment in which scripting was put on a solid basis with AWK, C-shell, and later Perl.

  • AWK was originally written in 1977, and distributed with Version 7 Unix. The book The AWK Programming Language, the first scripting book was published 1988.

  • C shell (csh) was written by Bill Joy and first distributed with BSD in 1979.

  • The first important non-Unix scripting language that was more or less widely used was probably REXX which was designed and first implemented between 1979 and mid-1982 by Mike Cowlishaw of IBM.  

  • Perl was first released in 1987.
     

• The level of incompetence of A&T management

• Microsoft contributions to Unix

• Real vs. imaginable contributions of Unix to the OS field  (IMHO Unix first of all the first system that created component model of programming with shell and pipes as "glue" between components)

• Limits in complexity of OSes. Is Unix excessive complexity (this was an OS designed by developers for developers) the key problem which prevented it wider adoption.  MS-DOS backlash (MS DOS and later Windows essentially wiped clean Unix from the desktop; Linux lately slightly reversed the trend) and its significance. 

• Flaws in design of C and their influence on Unix in general  and Unix security in particular.

Multics seems to be a dramatically under-appreciated predecessor of Unix -- all key Bell Labs folks that participated in Unix development were trained in Multics and borrowed a lot from this system including the key idea of the hierarchical filesystem, many commands (ls, ps, etc) as well as the key idea of using high level language for writing OS. C language was essentially a simplified dialect of PL/1 with BCPL address arithmetic (see also links in Multics Home page). For example Thompson in recent interview stated:

Thompson. The one thing I stole was the hierarchical file system because it was a really good idea—the difference being that Multics was a virtual memory system and these "files" weren't files but naming conventions for segments. After you walk one of these hierarchical name spaces, which were tacked onto the side and weren't really part of the system, you touch it and it would be part of your address space and then you use machine instructions to store the data in that segment. I just plain lifted this.

By the same token, Multics was a virtual memory system with page faults, and it didn't differentiate between data and programs. You'd jump to a segment as it was faulted in, whether it was faulted in as data or instructions. There were no files to read or write—nothing you could remote—which I thought was a bad idea. This huge virtual memory space was the unifying concept behind Multics—and it had to be tried in an era when everyone was looking for the grand unification theory of programming—but I thought it was a big mistake.

The good, but biased (bashing of Multics is completely misguided and from the point of view of Unix history completely stupid) description of origins and history of UNIX can be found at Origins and History of Unix, 1969-1995

Information about the history of Linux, one of the most recent Unix re-implementations, can be found at Nikolai Bezroukov. Portraits of Open Source Pioneers. Ch 4: A Slightly Skeptical View on Linus Torvalds

See also my review of  A Quarter Century of UNIX

Old News ;-)

[Dec 15, 2007] Unsung innovators Robert Kahn, the 'stepfather' of the Internet

One big moment that isn't often recognized, he says, is when DARPA -- working with a number of contractors, including Collins Radio, BBN and others -- demonstrated the first successful TCP connection traversing three dissimilar but interconnected networks. November 22, 2007, marked the 30th anniversary of that demo.

... ... ..

After his stint at DARPA, Kahn didn't stop pioneering. In 1986, he started the Corporation for National Research Initiatives (CNRI). The Reston, Va.-based organization helps shepherd various technology infrastructure projects. With funding from the National Science Foundation and DARPA, the CNRI helped create the first Gigabit networks operating at speeds above 1 billion bits per second. The CNRI also funded the development of Mosaic, the first popular Web browser, at the University of Illinois.

[Sep 14, 2006] ONLamp.com Confessions of a Recovering NetBSD Zealot by Federico Biancuzzi

...Charles M. Hannum: I'm one of the creators of the NetBSD Project, and served as its de facto technical lead for a long time. I was also involved in creating the NetBSD Foundation, and served as its president and chairman of the board. (Note: I was never the Foundation's secretary or treasurer.)

How did the NetBSD Project start?

Charles M. Hannum: The four people who started NetBSD were Chris Demetriou, Adam Glass, Theo de Raadt, and me. At the time, Chris and Adam were attending Berkeley and close to graduating. Theo was working for a living. I was doing other things. Chris is still sort of around, but doesn't really do anything; Adam went to work at Microsoft and is now lost to us; and we all know about Theo. There is some info in the NetBSD entry on Wikipedia.

I think the most striking difference between late 1992 and today is that there really was no "web." The original software had been released, and some of us had started using it for small (non-graphical!) websites, but it was still very much a hobbyist thing. More people were getting "email accounts" of various types, but penetration of the internet into homes was still quite low. Even so, this was near the end of the NSFNet era, and there were increasing problems with the backbone being overloaded. There were also some as-yet-undiscovered problems with TCP flow control which caused additional performance problems. And lastly, nobody had started taking network security seriously.

On the open source side, you could liken it to the Stone Age. The operating systems (primarily 386BSD 0.1 and Linux 0.12) were nothing to write home about; they were buggy and incomplete. There were no "desktop" packages or "office" suites of any significance. (I actually ported Applixware to NetBSD under contract, because a certain blue company wanted it for their thin clients that ran NetBSD.) Development of X was hampered by the dissolution of the X Consortium and a vacuum of leadership there. We discovered later that GCC development was also being hampered by mismanagement (since fixed).

What I'd like to stress is that there was no Dummies Guide to Starting an Open Source Project. The term "open source" wasn't even being used yet, but that's beside the point. We were the first big collaborative project to use a version management system. (As examples, Linux used none, and most GNU software at best used "backup files" for version management.) There were no previous successes--or really even significant failures--to look at for guidance about how to organize the project. So we made it up.

I want to elaborate on the point about network security a little. Keep in mind that, in this time frame, most people were still using rlogin and unencrypted telnet. Buffer overflows were rampant. I (and other people) had already started doing experiments with subverting web sites; we all knew it was possible then, but nobody cared. It was several years before most people saw the writing on the wall and started clamping down access to central repositories and whatnot. Even today, most software distributions on the net (and this includes NetBSD) are not signed.

The primary reason for starting NetBSD at that time, ironically enough, is that there was a perceived lack of management in 386BSD. The actual 386BSD release only ran on a handful of systems, and was quite buggy. There was a rapidly growing community around it nonetheless, and many people had contributed patches. However, 386BSD's leader simply vanished. Nobody had any idea what he was doing, or whether he was even looking at the patches or working on another release. Eventually we decided that the only answer was to make a go of it ourselves--that's right, it all started with a fork.

Would you like to talk about the fork that originated OpenBSD?

Charles M. Hannum: No.

Since it came up in the /. thread, though, I would like to make one correction. It's widely claimed that I'm "the one" who ejected Theo from the NetBSD community. That is false. At that time in NetBSD's history, Chris G. Demetriou was playing the role of alpha male, and I wasn't even given a choice. I was certain it was going to bite us in the ass. I think the question for historians is not whether it did bite us in the ass, but how many times and how hard.

Why did you focus on portability?

Charles M. Hannum: At the very beginning, this was not actually a focus. It quickly became apparent that there were a large number of people interested in NetBSD (and open source OSes in general) who were currently on non-x86 platforms. Remember that this was still the 80486 era--PC processors weren't very good. Most "workstation"-class computers were based on something else--a myriad of Motorola 68k and 88k, SPARC, POWER, etc. On the HP9000/300 and SPARC platforms, we also had the advantage of access to code already written--though in both cases the integration was complex, and the code only supported a handful of systems at first.

I was also hanging out (and occasionally doing some work) at the Free Software Foundation, where there were a lot of HP9000/300s--running MORE/BSD, which had long since been abandoned. So I set out to get NetBSD running on these machines. Just getting a cross compiler working at the time was quite a bear, but it didn't take too long before these machines were all running NetBSD.

Yes, several of the earliest NetBSD development systems were owned by the Free Software Foundation.

With working 68k support in hand, we quickly spawned Amiga and Mac development groups. I then helped Theo get the SPARC support from LBL integrated. The whole thing snowballed.

Of course, the fact that you've ported the system to tons of machines does not mean you have good portability. We were still in the days of "copy and edit"--and so, for example, although the Amiga and Mac code [was] heavily cribbed from the HP9000/300 code, they were separate and had different features and bugs. Trying to fix bugs in this environment was making me crazy--and wasting a lot of time--and eventually I just started smashing the code together at high speed and sifting out the common parts. Other developers followed ("lead by example" works sometimes), and so this led into our global thinking about portability architecture, shared device drivers, etc. Oddly enough, Microsoft was working on similar ideas at the same time, in the development of Windows NT.

How was the relationship with hardware manufacturers at that time?

Charles M. Hannum: Terrible. We rarely got documentation from anyone. I actually wrote a lot of device driver code by guessing what the device was supposed to do. (Lots of previous experience reverse-engineering code helped there, I'm sure.) We had severe problems trying to deal with things like the "programmable" Adaptec SCSI controllers that became very popular; it was so bad that I was honestly talking about staging a sit-in at Adaptec HQ, and probably should have done it.

There were some notable exceptions, though. It took a while, but NCR, and later LSI, finally came around and dropped a heaping pile of (fairly good) documentation on me for their SCSI controllers. We did eventually get some material out of BusLogic, but only for their older "heavyweight" controllers (what we call "bha"<-- should bha be in code style? -->).

Intel, for its part, has been pretty good about putting CPU and chipset documentation online for the last several years, which I applaud, but their networking documentation (both wired and wireless) has been extremely poor. The strangest part of the Intel story was when the i82559 manual became restricted, even though it was substantially identical to the i82557 manual [that] had been published in their networking databooks earlier. Most other companies producing Ethernet controllers have been decent to us, except for Broadcom and Marvell, which have [each] been a 100% loss. Wireless vendors have generally been a tremendous annoyance, generating excuses but no documentation--I think Atmel and Realtek are the only exceptions.

We got some scattered documentation from other companies--e.g. Ensoniq and Realtek--but it's sometimes been incomplete and very difficult to make sense of.

Fortunately we didn't have to deal with most of the PC video card circus ourselves; XFree86 and now X.org have taken care of that.

What type of relationship did you have with the license? Is this relationship changed during the time?

Charles M. Hannum: Most of us had a very strong distaste for the so-called "virus" clause in the GPL, and this is the primary reason we did not adopt it. There was also some thinking that CSRG (Berkeley) and the X Consortium had been successful with leaner, looser licenses, so why bother. In retrospect I think this was naive; if you look at the history, you'll see that neither CSRG nor the X Consortium were really successful in getting third parties to contribute back most of their changes--and so what we really got in both cases was a long list of derived but very different, and often incompatible, systems.

Linux has not been wholly successful in this either, and today there are myriad distributions which are subtly incompatible. However, they definitely did better.

If I were doing it again, I might very well switch to the LGPL. I'll just note that it didn't exist at the time.

How much did the (in)famous BSD lawsuit hit NetBSD code base and popularity?

Charles M. Hannum: There was a lot of FUD around this issue--some of it from Linus, actually--and it did cause us some problems. The reality is that we had a signed agreement with USL that essentially said we had to upgrade certain files from their Net/2 versions to 4.4-Lite, and not distribute some other files at all (which we never used in the first place). We were in the process of moving to a 4.4-Lite base anyway, so this had virtually no impact on development. It did, however, delay making our CVS history public--far longer than it should have--because we needed to remove some of that early history in order to meet the conditions of the agreement.

I've never seen the similar agreement between USL and FreeBSD, but my understanding from what I've heard is that it is quite different. This caused some more FUD to be generated, because apparently what we did would not have met the terms of FreeBSD's agreement.

Had Novell not bought USL when it did, it's unclear to me how this would have panned out. I've never been able to convince myself that Berkeley was in the "right." However, Novell put a swift end to the suit, the agreement is very clear, and nobody cares about that early code history any more--so this is all water under the bridge.

Have you read the legal settlement after it was recently made public? Any surprise?

Charles M. Hannum: Yes, I read it. The first thing to note is that this agreement was with Berkeley. We executed a separate agreement with USL (which has not been made public), and that is what governs our relationship. There were no surprises when we read the settlement, but it wasn't really relevant to us.

If you had a separate agreement, you were free to work on your software without problems. Do you think that the general and chaotic FUD about the lawsuit hit you even if you had already solved the problem?

Charles M. Hannum: Absolutely it hurt us. A lot of people (and I don't want to be divisive, but honestly they were mostly Linux proponents, including Linus himself) spread FUD for years about BSD systems being "unsafe"--even after the UCB/USL lawsuit was settled. The fact is that there was no danger in using NetBSD in a product, and a number of companies did so.

How was NetBSD funded during these years? Who managed these funds and how?

Charles M. Hannum: In the beginning, we just put the machines on the UCB and MIT AI lab networks, because we had access to do that and nobody minded. The server equipment was purchased by Chris Demetriou. The project per se had no "funds." Later on, colo space and machines were donated by a variety of organizations (NASA, iki.fi and hut.fi, etc.), and again no money changed hands. Later on we started collecting donations to purchase hardware; colo space was (and is) still donated, primarily by ISC now.

As far as funding marketing work, such as conference appearances and merchandise, most of that was paid for by me, d.b.a. The NetBSD Mission. A fraction of the cost of the Comdex booths was paid for by LinuxMall. Most of the other conferences gave us "free" booths--that means the conference itself didn't charge for the booth, but we (I) still had to pay for everything else (carpeting, furniture, shipping or renting equipment, union labor, etc.). Producing CDs and T-shirts to give away (we tried selling them at conferences, but that didn't go over well, especially at Comdex) was also fairly expensive; it adds up quickly.

Do you have any regret about the way NetBSD promoted the project and did advocacy at conferences around the world?

Charles M. Hannum: No. Unfortunately there is no longer a concerted effort to do this, and particularly to give away copies that people can try. Frankly I'm not sure (and wasn't even then) that giving away copies to install on a PC will impress people much anyway, given that NetBSD's installer is still very primitive compared to the Linux distros. Many reviews have focused on this and lambasted NetBSD for it.

[July 5, 2005 ] LinuxPlanet - Reviews - Classic UNIX Programming Text Updated - Interview with Steve Rago, Co-author of Advanced Programming in the UNIX Environment

Ibrahim Haddad
Tuesday, July 5, 2005 12:18:35 PM

After 13 years, Addison-Wesley has published an update to a classic UNIX System programming text: Advanced Programming in the UNIX Environment. After the death of the original author, Rich Stevens, in 1999, it was difficult to find someone to tackle a project this big. We recently caught up with the co-author, Steve Rago, to get a behind-the-scenes look at this project.

Steve, you were one of the developers of UNIX System V Release 4. Can you tell us more about your background and contributions and how you became the co-author of the second edition of one of the most popular UNIX books?

After getting a BE and MS from Stevens Institute of Technology, I got a job working in the UNIX System V Development Laboratory at AT&T Bell Labs. I had wanted to work at Bell Labs, where my father worked, since I was 12 years old. Ironically, a year after joining Bell Labs, AT&T reorganized us into a different business unit, so we weren't Bell Labs anymore. I started out working on System V Release 2.0, helping to maintain and benchmark the VAX port. Eventually, I worked on networking software, which led me to STREAMS. After most of the original STREAMS developers completed the port of Dennis Ritchie's streams to System V Release 3, I ended up taking over responsibility for it somewhere between SVR3.1 and SVR3.2. During SVR4 development, I enhanced the STREAMS mechanism, converted the open file table to use dynamically-allocated memory (thus removing the historic NOFILE limit to a UNIX process's open files), moved the poll(2) system call under the vnode framework, and did a lot of general clean-up work in the kernel.

I spent 7 years at AT&T, then left for a small start-up company just before AT&T created USL. I worked on file systems, writing one that transparently compressed and uncompressed files on the fly, and another that sped up system throughput and used an intent log for fast recovery. These were eventually ported to the SCO OpenServer V UNIX System. Then I developed stackable file systems for commercial UNIX systems. The file system business evolved into a file server business, and then the company was bought by EMC, where I still work as a manager of one of the file system groups. In total, I have about 20 years of UNIX programming experience, both kernel-level and user-level.

Since I was involved in the review of the first edition of APUE, Addison-Wesley contacted me for suggestions for candidates to update the book. I wanted the book to be updated properly, the way Rich would have wanted, and to honor his memory, so I volunteered for the project.

Why did you update APUE and how does the second edition of APUE differ from the first edition? Where did you have the most changes?

Rich's book is a classic, but the world has changed a lot since it was first published in 1992. Standards have evolved, UNIX system implementations have come and gone, and technology has advanced significantly. I added a chapter on sockets, two chapters on threads, and totally rewrote the chapter on communicating with a printer to reflect the technological advancement from a serial PostScript printer to a network-attached PostScript printer. I removed the chapter that dealt with modem communication, but I made it available on the book's Web site. Other than the printer chapter, Chapter 2 shows the most change. It deals with standards, and these have changed significantly over the past 13 years. One other major change is that I shifted the implementation focus from 4.3+BSD and SVR4 to more contemporary platforms: FreeBSD 5.2.1, Linux 2.4.22, Mac OS X 10.3, and Solaris 9. (The source code for the examples is also available on the book's Web site.)

Daemon News Seen it all before

• Of course, the idea of actually executing this unknown program is ridiculous. We went through all that over a decade ago, when Robert T. Morris, Jr. let loose the famous Internet Worm and took down a whole lot of BSD systems. We hadn't paid much attention to security up till then, but we certainly did in the aftermath. Now, ten years later, it appears that people still haven't learnt. We have three major problems:

  • Microsoft actively encourages people to transmit executable programs. Sure, we can do that in UNIX as well, but we don't. That's not because UNIX runs on multiple platforms: more and more programs are being written in interpretative languages such as perl and tcl, and if this worm had been written in one of these languages, it would have the potential to damage UNIX systems as well as Microsoft systems. The real reason we don't transmit executable programs is that the whole idea is such a security risk that it seems completely absurd.

  • Microsoft has done nothing to protect systems. This isn't the first time that a massive security breach has been propagated by e-mail, yet their systems don't have any concept of security, the program can do whatever it wants. If I were designing an execution environment for executable mail attachments, I'd put it in its own directory and chroot it there, so that it couldn't access the rest of the system.

  • Users haven't learnt either. I heard that one British publisher has apparently lost all its image data, which was stored on disk. What would they have done if the disk had failed? This seems to be a general problem with Microsoft users: they don't make backups.

• This message caused damage comparable in magnitude to Bill Gates' personal fortune. Who's to blame? Not really the perpetrator. We know how to stop this damage. In the UNIX world, we stopped it a decade ago. Microsoft knows about the dangers, but has done nothing to stop it.

• It's a pity that the press didn't see this. I haven't heard a single mention in the press that the vendor of the software might be to blame. Even so, though, it makes the man in the street more aware of security issues, and that can only be to the benefit of secure operating systems.

• So what is the difference between BSD and Linux?

• On a different topic, I've been doing some work on describing the differences between BSD and Linux lately. Given the similarity between the systems, it's not surprising that people keep asking what the differences are. Here's the current state of a document I'm writing on the subject.

• Any comparison has to be subjective, but I'm trying to be fair to everybody here. If you find something incorrect or disadvantageous to any side, including Linux, please let me know.
   

SCO - Ancient UNIX

The Unix Heritage Society

Open Resources Twenty Years of Berkeley Unix

Stanford Computer History Pages:

• A Brief History of UNIX
• Back to SUN

Feature OMU - One Man Unix

In the late 1970s and early 1980s (the good old days of "hobby computing") before the IBM PC and its clones took over the world Steve Hosgood built a Unix clone at home. He was used to V7 Unix on the PDP-11 at university and wasn't keen to step backwards 10 years to the technology of CP/M and BASIC programming.

He did not know that eight years later a guy called Linus Torvalds was going to think the same thoughts and do much the same things. The big difference was that he was in the right place and the right time and had internet connectivity - Steve didn't have any of these advantages!

Daemon News 199903 A History of UNIX before Berkeley UNIX® Evolution, 1975-1984 -- very good.

[Jan 27, 2002]Slashdot Caldera releases original unices under BSD license

Caldera International has done a very good thing. They have released the "Ancient" Unices they inherited when they purchased SCO under a "BSD-style" license. The license is available here, instructions on finding the source are here. Caldera (and before that SCO) had required people to obtain a free (as in beer) but somewhat restrictive license in order to get these old sources. The new BSD-style licensing only applies to the 16-bit PDI-11 versions and some of the early 32-bit releases (excluding System III and System V), but it's still very cool.

The Unix archives are available via http://www.tuhs.org/archive_sites.html. The Unix Heritage Society website is at http://www.tuhs.org/. And the PDP Unix Preservation Society (PUPS) Home Page is at http://minnie.tuhs.org/PUPS/. This webpage has information on installing and running the software.

According to the PUPS FAQ, the Santa Cruz Operation (SCO) owned Unix research editions 1 to 7, PWB/UNIX, Mini-UNIX, 32V, System III, System V, and parts of 2.xBSD. In May, 2001, Caldera completed the acquisition of SCO's Server Software and Professional Services divisions, and SCO's UnixWare and OpenServer technologies. (The Santa Cruz Operation already provided free personal source code licenses.)

UNIX Chronology

Datametrics--The UNIX Industry A Brief History -- a transcript of a very interesting talk by Dr. Kelly who gave this talk at the 1995 Spring Unite Conference, a users group meeting for Unisys customers.

History of the Usenet

• Ch 1 The Net and Netizens The Impact of the Net on People's Lives
• Ch 2 The Evolution of Usenet The Poor Man's ARPANET
• Ch 3 The Social Forces Behind the Development of Usenet

History of the ukr Internet K.I.S.S.
 

[Nov. 30, 1999] A Brief Histroy of the 'ls' command LG #48
 

[June 11, 1999] The Unix War: Epilogue.
 

Netizens Netbook
 

AN ARTICLE ABOUT LINUX AND ITS SIGNIFICANCE (1994)
 

[Feb. 7, 1999]The return of BSD - SunWorld - January 1999

I's been a long while, but finally people are coming to accept Solaris, the System V-based operating system that replaced SunOS 4. Still, six years is a long time, and it would have taken much longer if Sun had continued to maintain SunOS 4. Why such loyalty? They are, after all, both versions of Unix.

The last thing I want to do here is revive the SunOS vs. Solaris debate, but I will draw attention to the biggest single difference between SunOS 4 and SunOS 5, the operating system component of today's Solaris: SunOS 4 is based on 4.2 BSD, the version of Unix developed at the University of California at Berkeley and the first operating system with support for TCP/IP. By contrast, SunOS 5 (commonly called Solaris, though that's not quite accurate) is based on AT&T's Unix System V.4. BSD is different enough from System V that six years after the "death" of SunOS 4, it still has a large number of supportsignificantly hampered when Unix System Laboratories (USL) filed a lawsuit against BSDI, alleging abuse of AT&T source code.

Historically, each project was founded after differences of opinion about what constituted a good operating system. Since the software is free, any group of people can decide to custom build their own operating system. If it doesn't work, they can just stop building. In fact, all current BSD varieties, including BSDI, stem from Bill Jolitz's 386 BSD project, which faded into oblivion in 1994.

On the face of it, this doesn't seem to be a good approach: why not bite the bullet and compromise? In practice, the system shows remarkable self-regulating tendencies: 386 BSD is the only project that has closed up shop, and its descendents are all doing well and actively cross-pollinating. The fact that each version has a different kernel means survival of the fittest applies to kernel code as well, whereas in Linux it applies only to user code. For example, the fledgling FreeBSD SPARC port didn't start from scratch: it started from the NetBSD implementation and immediately raised the question, What can we do better? This process automatically raises the standard necessary for success. As a result, many such attempts fail, but the ones that don't create world-class code.

Recommended Links

• Unix - Wikipedia, the free encyclopedia
• The History of UNIX
• UNIX history (preview)
• Open Sources Voices from the Open Source Revolution

  Twenty Years of Berkeley Unix From AT&T-Owned to Freely Redistributable Marshall Kirk McKusick

• Early Unix history and evolution
• The Creation of the UNIX Operating System -- slightly biased toward AT&T view on unix histroy. Still a nice intro.

• M. McKusick, K. Bostic, 4.4 Berkeley Software Distribution, Five volumes of documentation and software, comprised of: User's Reference Manual, ISBN 1-56592-075-9, User's Supplementary Documents, ISBN 1-56592-076-7, Programmer's Reference Manual, ISBN 1-56592-078-3, Programmer's Supplementary Documents, ISBN 1-56592-079-1, System Manager's Manual, ISBN 1-56592-080-5, CD-ROM Companion, ISBN 1-56592-081-3 (Domestic), ISBN 1-56592-092-9 (International). O'Reilly & Associates, Inc. 103 Morris Street, Suite A Sebastopol, CA 94572, April 1994.

  BSDCon 2000 Keynote

• Xah The Unix Pestilence
• A Report on The Internet Worm
• Daemon News 1999/03 A History of UNIX before Berkeley UNIX® Evolution, 1975-1984 -- one of the best reviews of Unix history I had found.

  This article traces some of the intermediate history of the UNIX Operating System, from the mid nineteen-seventies to the early eighties. It is slightly updated from an article that appeared as ``The Evolution of UNIX from 1974 to the Present, Part 1'' in Microsystems[Darw1984a]. It was intended as part 1 of 3; unfortunately, that issue was also the last issue of Microsystems. This article discusses ``Research UNIX'': V6, V7 and V8; and tells the tale of many programs and subsystems that are today part of 4.4 BSD, System V or both. Subsequent articles were planned to discuss in more detail the history of Berkeley UNIX, System V, and commercialized UNIXes. We have not written those other articles; this article is being submitted to DaemonNews in hopes that those who have written other histories of other parts of UNIX's history will come forward.

• A Brief History of UNIX  by Mike Loukides. Very interesting article which is somewhat skeptical about Linux.

Classic papers from Bell Lab

• BSTJ version of C.ACM Unix paper -- one of the most famous papers in computer science.
   

  D. M. Ritchie and K. Thompson
  ABSTRACT

  Unix is a general-purpose, multi-user, interactive operating system for the larger Digital Equipment Corporation PDP-11 and the Interdata 8/32 computers. It offers a number of features seldom found even in larger operating systems, including

  i

  A hierarchical file system incorporating demountable volumes,

  ii

  Compatible file, device, and inter-process I/O,

  iii

  The ability to initiate asynchronous processes,

  iv

  System command language selectable on a per-user basis,

  v

  Over 100 subsystems including a dozen languages,

  vi

  High degree of portability.

  
  This paper discusses the nature and implementation of the file system and of the user command interface.

  NOTE: * Copyright 1974, Association for Computing Machinery, Inc., reprinted by permission. This electronic edition of this paper is a reprint of the version appearing in The Bell System Technical Journal 57 no. 6, part 2 (July-August 1978). In turn, that was a revised version of an article that appeared in Communications of the ACM, 17, No. 7 (July 1974), pp. 365-375. That article was a revised version of a paper presented at the Fourth ACM Symposium on Operating Systems Principles, IBM Thomas J. Watson Research Center, Yorktown Heights, New York, October 15-17, 1973. Most of the differences between versions occur between the C. ACM version and the BSTJ printing; we incorporated updated numbers and material on portability.

   

• The Evolution of the Unix Time-sharing System

  Dennis M. Ritchie
  Bell Laboratories, Murray Hill, NJ, 07974

  ABSTRACT

  This paper presents a brief history of the early development of the Unix operating system. It concentrates on the evolution of the file system, the process-control mechanism, and the idea of pipelined commands. Some attention is paid to social conditions during the development of the system.

   

  NOTE: *This paper was first presented at the Language Design and Programming Methodology conference at Sydney, Australia, September 1979. The conference proceedings were published as Lecture Notes in Computer Science #79: Language Design and Programming Methodology, Springer-Verlag, 1980. This rendition is based on a reprinted version appearing in AT&T Bell Laboratories Technical Journal 63 No. 6 Part 2, October 1984, pp. 1577-93.

  Introduction

  During the past few years, the Unix operating system has come into wide use, so wide that its very name has become a trademark of Bell Laboratories. Its important characteristics have become known to many people. It has suffered much rewriting and tinkering since the first publication describing it in 1974 [1], but few fundamental changes. However, Unix was born in 1969 not 1974, and the account of its development makes a little-known and perhaps instructive story. This paper presents a technical and social history of the evolution of the system.
   

• Bell Labs- Selected Technical Reports
• Dennis Ritchie Home Page
• You are not supposed to understand this. Dennis Ritchie comments on this comment on his web page Odd Comments and Strange Doings in Unix

• UNIX History Graphing Project

Unix philosophy

• Tenets of the UNIX Philosophy

  • Small is beautiful.
  • Make each program do one thing well.
  • Build a prototype as soon as possible.
  • Choose portability over efficiency.
  • Store numerical data in flat ASCII files.
  • Use software leverage to your advantage
  • Use shell scripts to increase leverage and portability.
  • Avoid captive user interfaces.
  • Make every program a filter.

Creators of Unix

Most of the key people for Unix project( Ken Thompson, Dennis Ritchie, Joe Ossanna, Bob Morris, Doug McIlroy, Brian Kernighan) came from Multics project were they were trained in OS design. Here is the relevant quote from UNIX and Multics:

When Bell Telephone Laboratories (BTL) joined with MIT Project MAC and General Electric's computer department to create the Multics project, BTL contributed some of the finest programmers in the world to the team. I first met Ken Thompson because he had written a slick editor for CTSS called QED. It was descended from QED on the SDS-940, but was quite different because Ken had added regular expressions to it, and made many other changes. (Ken had published a paper on compiling regular expressions into machine code just before joining the Multics project.) Ken worked on the Multics I/O switch design. Dennis Ritchie and Rudd Canaday were BCPL jocks. Joe Ossanna worked on the I/O system design and wrote one of the original six Multics papers; Bob Morris, Doug McIlroy, Dave Farber, and Jim Gimpel worked on EPL, Stu Feldman worked on the I/O switch, Peter Neumann managed the team and worked on file system design, Brian Kernighan worked on the support tools.

Ken Thompson

• Ken Thompson home page. See also entries in Jargon file

  • Ken Thompson - Wikipedia, the free encyclopedia

  • Reflections on Trusting Trust -- Turing lecture. Published in Communication of the ACM, Vol. 27, No. 8, August 1984, pp. 761-763. Here is the introduction:

    Thank the ACM for this award. I can't help but feel that I am receiving this honor for timing and serendipity as much as technical merit. UNIX swept into popularity with an industry-wide change from central main frames to autonomous minis. I suspect that Daniel Bobrow (1) would be here instead of me if he could not afford a PDP-10 and ad had to "settle" for a PDP-11. Moreover, the current state of UNIX is the result of the labors of a large number of people.
    
    There is an old adage, "Dance with the one that brought you," which means that I should talk about UNIX. I have not worked on mainstream UNIX in many years, yet I continue to get undeserved credit for the work of others. Therefore, I am not going to talk about UNIX, but I want to thank everyone who has contributed.
    
    That brings me to Dennis Ritchie. Our collaboration has been a thing of beauty. In the ten years that we have worked together, I can recall only one case of miscoordination of work. On that occasion, I discovered that we both had written the same 20-line assembly language program. I compared the sources and was astounded to find that they matched character-for-character. The result of our work together has been far greater than the work that we each contributed.
    
    I am a programmer. On my 1040 form, that is what I put down as my occupation. As a programmer, I write programs. I would like to present to you the cutest program I ever wrote. I will do this in three stages and try to bring it together at the end.

  • Bibliography ken

• Dennis Ritchie Home Page

• Brian Kernighan

  • Why Pascal is Not My Favorite Programming Language  -- bold critique of Pascal when   "structured programming' ayatollah" ruled the world of programming ;-)

  • All the example code from The Unix Programming Environment

• Bill Joy

Chronology

UNIX History Unix Timeline by  Éric Lévénez

Datametrics--Handout for UNIX a Brief History

UNIX Chronology

Early Unix

• The Unix Time-sharing System -- the 1978 BSTJ update of the 1974 Communications of the ACM article by Dennis Ritchie and Ken Thompson originally describing Unix:
• The evolution of the UNIX time-sharing system
• Unix Notes from 1972
• Unix Programmer's Manual First Edition (1971)
• Seventh Edition Manual
• BCPL Reference Manual -- the language which Multics quietly pioneered. Dennis Ritchie was BCPL jock on Multics
• Users' Reference to B

Jargon File Resources

• back door -- one of the most clever hacks created ever ;-)
• CTSS
• Multics
• brute force
• demigod

Unix History  -- a rather funny version.

Early Unix Source

•  SCO Offers SCO Opens Source Code for Older UNIX [Feb 22, 2000]
  Santa Cruz Operations  has made a number of straight UNIX source codes available to the public.
  • Ancient UNIX Source Code Licenses

    Licenses are available for the following versions:

    Mini UNIX
    UNIX V6
    PWB UNIX
    UNIX V7 (which also covers Editions 1-5, and the 32V)
    
    Follow these instructions to obtain a source code license for "ancient" versions of UNIX.
    These licenses permit hobbyists and enthusiasts to have access to the source code of these historic releases, for personal and non-commercial use, and to share experiences and code updates with other authorized individuals having corresponding licenses. SCO has received numerous favorable responses from UNIX enthusiasts around the world, including messages such as, "Future computer historians will greatly appreciate what you have achieved!" and "I've wanted access to this material for nearly 20 years! Well done!"

BSD

• Executive Bios Bill Joy Since joining Sun from Berkeley in 1982, he has led Sun's technical strategy, spearheading its open systems philosophy. He designed Sun's Network File System (NFS), and was a co-designer of the SPARC microprocessor Architecture. In 1991 he did the basic pipeline design of UltraSparc-I and its multimedia processing features. This basic pipeline is the one used in all of Sun's SPARC microprocessors shipping today.

• Keith Bostic on the BSD tradition

• Explaining BSD

• Daemon News 199909 - Kirk McKusick Speaks at Usenix

• BSD History Chart

• IPv4 - Brief History

• Unix Differences. (from Unix FAQ)

• Company Information Sun History

• A Brief History of FreeBSD

• bsd-family-tree
• History (1980-90s)
• History of BSD T-shirts
• E-Business Network: Geek of the Week: Lynne Jolitz

  The E-Business Network's Geek of the Week show interviews Lynne Jolitz of 386BSD fame. The eShow description says "Lynne Jolitz talks about the creation of 386BSD, the first shareware BSD implementation for Intel platforms, and her current quest to combat the problem of etherlag." ("shareware"?)

  In the interview, she discusses some of the history and highlights of the 386BSD project. She said that the Berkeley Unix (Tahoe) only ran on old VAX machines before her work on the 386 platform. She said that they (Bill and Lynne) were overwhelmed with all the patches and fixes they received. Jolitz also mentioned that they "started playing with role-based security" and plug-n-play, and that many of their concepts have not been implemented yet.

  Watch (or listen to) the RealAudio show at Oracle.com's E-Business Network.

  On a related note, feel free to share your experiences or hints for using RealPlayer in the Talkbacks below.

• Explaining BSD

  Who provides support, service, and training for BSD?

  BSDI have always supported BSD/OS, and they have recently announced support contracts for FreeBSD.

  In addition, each of the projects has a list of consultants for hire: FreeBSD, NetBSD and OpenBSD.

  The BSD project home pages

  BSDI
  FreeBSD
  NetBSD
  OpenBSD

  Other references to BSD

  Riding the web wave
  Twenty Years of Berkeley Unix
  Whatever Happened to BSD?
  A new thorn in Microsoft's side?
  BSD's Big Break?
  Three Unixlike systems may be better than Linux.
  BSD a better OS than Linux?
  The legend of BSD
  Getting to know OpenBSD
  BSD Unix: Power to the people, from the code

Etc

• LJ #12 April 1995 Review A Quarter Century of Unix

• Unix Lore and History -- from USAIL

• History of Unix
• unix family tree

• On the Design of the UNIX operating System

• CHAC History Pages

• History of Unix from Understanding Unix Concepts

• Mach and Windows NT Operating Systems Compared -- paper by Mike Mike Podanoffsky
  25 St Anthony Drive Hudson, NH 03051 Email: mikep@world.std.com

Last modified: November 08, 2008