From: tmatimar@empress.com (Ted M A Timar)
Newsgroups: comp.unix.questions,comp.unix.shell,news.answers
Subject: Unix - Frequently Asked Questions (6/7) [Frequent posting]
Supersedes: <unix-faq/faq/part6_726386543@athena.mit.edu>
Followup-To: comp.unix.questions
Date: 21 Jan 1993 06:03:22 GMT
Organization: Empress Software
Distribution: world
Expires: 18 Feb 1993 06:02:22 GMT
NNTP-Posting-Host: pit-manager.mit.edu
X-Last-Updated: 1992/12/09

Archive-name: unix-faq/faq/part6
Version: $Id: part6,v 2.1 92/12/04 07:43:57 tmatimar Exp $

These seven articles contain the answers to some Frequently Asked
Questions often seen in comp.unix.questions and comp.unix.shell.
Please don't ask these questions again, they've been answered plenty
of times already - and please don't flame someone just because they may
not have read this particular posting.  Thank you.

These articles are divided approximately as follows:

      1.*) General questions.
      2.*) Relatively basic questions, likely to be asked by beginners.
      3.*) Intermediate questions.
      4.*) Advanced questions, likely to be asked by people who thought
	   they already knew all of the answers.
      5.*) Questions pertaining to the various shells, and the differences.
      6.*) An overview of Unix variants.
      7.*) An comparison of configuration management systems (RCS, SCCS).

This article includes answers to:

      6.1)  Disclaimer and introduction.
      6.2)  A very brief look at Unix history.
      6.3)  Main Unix flavors.
      6.4)  Unix Standards.
      6.5)  Identifying your Unix flavor.
      6.6)  Brief notes on some well-known (commercial/PD) Unices.
      6.7)  Real-time Unices.
      6.8)  Unix glossary.
      6.9)  Acknowledgements.

If you're looking for the answer to, say, question 6.5, and want to skip
everything else, you can search ahead for the regular expression "^6.5)".

While these are all legitimate questions, they seem to crop up in
comp.unix.questions or comp.unix.shell on an annual basis, usually
followed by plenty of replies (only some of which are correct) and then
a period of griping about how the same questions keep coming up.  You
may also like to read the monthly article "Answers to Frequently Asked
Questions" in the newsgroup "news.announce.newusers", which will tell
you what "UNIX" stands for.

With the variety of Unix systems in the world, it's hard to guarantee
that these answers will work everywhere.  Read your local manual pages
before trying anything suggested here.  If you have suggestions or
corrections for any of these answers, please send them to to
tmatimar@empress.com.

6.1)  Disclaimer and introduction.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      The following is offered with no guarantee as to accuracy or
      completeness.  I have done what I can in the time available and
      it still is very much work in progress.  I hope to keep improving
      this summary.  Comments welcome:  lew@bnr.ca.  Acknowledgements
      at the end.

      First a short definition.  By Unix we mean an operating system
      typically written in C, with a hierarchical file system,
      integration of file and device I/O, whose system call interface
      includes services such as fork(), pipe(), and whose user
      interface includes tools such as cc, troff, grep, awk, and a
      choice of shell.  Note that UNIX is a registered trademark of USL
      (AT&T), but will be used here in its generic sense.

      Most Unices (the more common plural form) are derived more or
      less directly from AT&T code (some code from the first C version
      is presumably still left in most), but there are also clones
      (i.e. Unix-compatible systems with no AT&T code).

      In addition, there are also Unix-like environments (e.g. VOS)
      sitting on top of other OSs, and OSs inspired from Unix (yes,
      even DOS!).  These are not covered here.  Little on real-time
      Unices yet (although more is planned).

      Unix comes in an incredible variety of flavors.  This is to a
      large extent due to availability of sources and the ease of
      porting and modifying Unix.  Typically, a vendor of Unix will
      start with one basic flavor (see below), take ideas/code from the
      other major flavor, add and change many things, etc.  This
      results in yet another new Unix flavor.  Today, there are
      literally hundreds of Unices available, the closest thing to
      standard Unix being (by definition) System V.

      This answer was put together mostly from information on the net
      and email.  Some specific sources are also mentioned in the
      appropriate sections.

6.2)  A very brief look at Unix history.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      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.  The name
      "Unix" was intended as a pun on Multics (and was written "Unics"
      at first -- UNiplexed Information and Computing System).

      For the first 10 years, Unix development was essentially confined
      to Bell Labs.  These initial versions were labeled "Version n" or
      "Nth Edition" (of the manuals), and were for DEC's PDP-11 (16
      bits) and later VAXen (32 bits).  Some significant versions
      include:

      V1 (1971):  1st Unix version, in assembler on a PDP-11/20.
	 Included file system, fork(), roff, ed.  Was used as a text
	 processing tool for preparation of patents.  Pipe() appeared
	 first in V2!

      V4 (1973):  Rewritten in C, which is probably the most
	 significant event in this OS's history: it means Unix can be
	 ported to a new hardware in months, and changes are easy.  The
	 C language was originally designed for the Unix operating
	 system, and hence there is a strong synergy between C and Unix.

      V6 (1975):  First version of Unix widely available outside
	 Bell Labs (esp.  in universities).  This was also the start of
	 Unix diversity and popularity.  1.xBSD (PDP-11) was derived
	 from this version.  J. Lions published "A commentary on the
	 Unix Operating System" based on V6.

      V7 (1979):  For many, this is the "last true Unix", an
	 "improvement over all preceding and following Unices"
	 [Bourne].  It included full K&R C, uucp, Bourne shell.  V7 was
	 ported to the VAX as 32V.  The V7 kernel was a mere 40
	 Kbytes!

         Here (for reference) 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.

      These Vn versions were developed by the Computer Research Group
      (CRG) of Bell Labs.  Another group, the Unix System Group (USG),
      was responsible for support.  A third group at Bell Labs was also
      involved in Unix development, the Programmer's WorkBench (PWB),
      to which we owe, for example, sccs, named pipes and other
      important ideas.  Both groups were merged into Unix System
      Development Lab in 1983.

      Work on Unix continued at Bell Labs in the 1980s.  The V series
      was further developed by the CRG (Stroustrup mentions V10 in the
      2nd edition of his book on C++), but we don't seem to hear much
      about this otherwise.  The company now responsible for Unix
      (System V) is called Unix System Laboratories (USL) and is
      majority-owned by AT&T.

      But much happened to Unix outside AT&T, especially at Berkeley
      (where the other major flavor comes from).  Vendors (esp. of
      workstations) also contributed much (e.g. Sun's NFS).

      The book "Life with Unix" by Don Libes and Sandy Ressler is
      fascinating reading for anyone interested in Unix, and covers a
      lot of the history, interactions, etc..  Much in the present
      section is summarized from this book.

6.3)  Main Unix flavors.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      Until recently, there were basically two main flavors of Unix:
      System V (five) from AT&T, and the Berkeley Software Distribution
      (BSD).  SVR4 is essentially a merge of these two flavors.  End
      '91, OSF/1 from the Open Software Foundation was released (as a
      direct competitor to System V) and may (future will tell) change
      this picture.

      The following lists the main releases and features of System V,
      BSD and OSF/1.

      System V from AT&T.  Typical of Intel hardware.  Most often
	 ported Unix, typically with BSD enhancements (csh, job
	 control, termcap, curses, vi, symbolic links).  System V
	 evolution is now overseen by Unix International (UI).  UI
	 members include AT&T, Sun, ....
	 Newsgroup: comp.unix.sysv[23]86.  Main releases:

         - System III (1982): first commercial Unix from AT&T
           - FIFOs (named pipes)  (later?)

         - System V (1983):
           - IPC package (shm, msg, sem)

         - SVR2 (1984):
           - shell functions (sh)
           - SVID (System V Interface Definition)

         - SVR3 (1986) for ? platforms:
           - STREAMS (inspired by V8), poll(), TLI (network software)
           - RFS
           - shared libs
           - SVID 2
           - demand paging (if hardware supports)

         - SVR3.2:
           - merge with Xenix (Intel 80386)
           - networking

         - SVR4 (1988), mainstream of Unix implementations, merge of
	   System V, BSD, and SunOS.
           - From SVR3: sysadmin, terminal I/F, printer (from BSD?),
	     RFS, STREAMS, uucp
           - From BSD: FFS, TCP/IP, sockets, select(), csh
           - From SunOS: NFS, OpenLook GUI, X11/NeWS, virtual memory
	     subsystem with memory-mapped files, shared libraries
	     (!= SVR3 ones?)
           - ksh
           - ANSI C
           - Internationalization (8-bit clean)
           - ABI (Application Binary Interface -- routines instead of traps)
           - POSIX, X/Open, SVID3

         - SVR4.1
           - async I/O (from SunOS?)

         - SVR4.2 (based on SVR4.1ES)
           - Veritas FS, ACLs
           - Dynamically loadable kernel modules

         - Future:
           - SVR4 MP (multiprocessor)
           - Use of Chorus microkernel?

      Berkeley Software Distribution (BSD).  Typical of VAXen, RISCs,
	 many workstations.  More dynamic, research versions now than
	 System V.  BSD is responsible for much of the popularity of
	 Unix.  Most enhancements to Unix started here.  The group
	 responsible at UCB (University of California at Berkeley) is
	 the Computer System Research Group (CSRG).  They closed down
	 in 1992.  Newsgroup: comp.unix.bsd.  Main releases:

         (much reorganized wrt dates and releases, hope it's converging)

         - 2.xBSD (1978) for PDP-11, still of significance? (2.11BSD
	   was released in 1992!).
           - csh

         - 3BSD (1978):
           - virtual memory

         - 4.?BSD:
           - termcap, curses
           - vi

         - 4.0BSD (1980):

         - 4.1BSD (?): base of later AT&T CRG versions
           - job control
           - automatic kernel config
           - vfork()

         - 4.2BSD (1983):
           - TCP/IP, sockets, ethernet
           - UFS: long file names, symbolic links
           - new reliable signals (4.1 reliable signals now in SVR3)
           - select()

         - 4.3BSD (1986) for VAX, ?:
         - 4.3 Tahoe (1988): 4.3BSD with sources, support for Tahoe
	   (32-bit supermini)
           - Fat FFS
           - New TCP algorithms
         - 4.3 Reno (1990) for VAX, Tahoe, HP 9000/300:
           - most of P1003.1
           - NFS (from Sun)
           - MFS (memory file system)
           - OSI: TP4, CLNP, ISODE's FTAM, VT and X.500;  SLIP
           - Kerberos

         - 4.4BSD (will we ever see it?) for HP 9000, Sparc, 386, DEC, Tahoe:
           - new FS organization, new process internals, new virtual
	     memory based on Mach 2.5
           - POSIX compatibility
           - OSI (based on ISODE), X.25

      The Open Software Foundation (OSF) released its Unix called OSF/1
	 end of 1991.  Still requires an SVR2 license.
	 Compatible/compliant with SVID 2 (and 3 coming), POSIX,
	 X/Open, etc..  OSF members include Apollo, Dec, HP, IBM, ....

         - OSF/1 (1991):
           - based on Mach 2.5 kernel
           - symmetric multiprocessing, parallelized kernel, threads
           - logical volumes, disk mirroring, UFS (native), S5 FS, NFS
           - enhanced security (B1 with some B2, B3; or C2), 4.3BSD admin
           - STREAMS, TLI/XTI, sockets
           - shared libs, dynamic loader (incl. kernel)
           - Motif GUI

         - Future:
           - OSF/1 MK (mikrokernel) based on Mach 3.0

      This list of major flavors should probably also include Xenix
      which has been the basis for many ports.  Derived from V7, S III
      and finally System V, it is similar externally but significantly
      changed internally (performance-tuned for micros).


      Two very good books describe the internals of the two main flavors.
      These are:
      - System V: "Design of the Unix Operating SYstem", M.J. Bach.
      - BSD: "Design and Implementation of the 4.3BSD Unix Operating System",
        Leffler, McKusick, Karels, Quaterman.
      For a good introduction to OSF/1 (not quite as technical as the
      previous two), see: "Guide to OSF/1, A Technical Synopsis",
      published by O'Reilly.  On SunOS, "Virtual Memory Architecture in
      SunOS" and "Shared Libraries in SunOS" in Summer 1989 USENIX
      Proceedings.

      A good set of articles on where Unix is going is "Unix Variants"
      in the Apr 92 issue of Unix Review.  Other good sources of
      information include the bsd-faq file, and many of the newsgroups
      mentioned in the text.

6.4)  Unix Standards.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      This section briefly describes the more important standards
      relevant to Unix.

      - IEEE:
        - 802.x (LAN) standards (LLC, ethernet, token ring, token bus)
        - POSIX (ISO 9945?): Portable Operating System I/F (Unix, VMS
	  and OS/2!) (only ? have been finalized at this point)
          - 1003.1:  library procedures (mostly system calls) -- roughly V7
                     except for signals and terminal I/F (1990)
          - 1003.2:  shell and utilities
          - 1003.3:  test methods and conformance
	  - 1003.4:  real-time: binary semaphores, process memory
		     locking, memory-mapped files, shared memory,
		     priority scheduling, real-time signals, clocks and
		     timers, IPC message passing, synchronized I/O,
		     asynchronous I/O, real-time files
          - 1003.5:  Ada language bindings
          - 1003.6:  security
          - 1003.7:  system admin (incl. printing)
          - 1003.8:  transparent file access
          - 1003.9:  FORTRAN language bindings
          - 1003.10: super computing
          - 1003.12: protocol-independent I/Fs
          - 1003.13: real-time profiles
          - 1003.15: supercomputing batch I/Fs
          - 1003.16: C-language bindings (?)
          - 1003.17: directory services
          - 1003.19: FORTRAN 90 language bindings

      - X/Open (consortium of vendors):
        - X/Open Portability Guides (XPGn):
          - XPG2 (1987), strong SV influence
            Vol 1:  commands and utilities
            Vol 2:  system calls and libraries
            Vol 3:  terminal I/F (curses, termio), IPC (SV),
		    internationalization
            Vol 4:  programming languages (C, COBOL!)
            Vol 5:  data management (ISAM, SQL)
          - XPG3 adds: ?
        - XOM series of interfaces:
          - XOM (X/Open Object Management) generic I/F mechanisms for
	    following
          - XDS (X/Open Directory Service)
          - XMH (X/Open Mail ??)
          - XCM (X/Open Consolidated Management) (not yet approved?)

      - AT&T
        - System V Interface Definition (SVID)
          - SVID1 (1985, SVR2)
            Vol 1:  system calls and libraries (similar to XPG2.1)
          - SVID2 (1986, SVR3)
            Vol 1:  system calls and libraries (base, kernel extensions)
            Vol 2:  commands and utilities (base, advanced, admin, software
                    development), terminal I/F
            Vol 3:  terminal I/F (again), STREAMS and TLI, RFS
          - SVID3 (19??, SVR4) adds
            Vol 4:  ??  &c
        - APIs
          - Transport Library Interface (TLI)
          - ACSE/Presentation Library Interface (APLI)

6.5)  Identifying your Unix flavor.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      This section lists a number of things you can look at in
      attempting to identify the base flavor of your Unix.  Given the
      significant exchange of code and ideas between the various
      flavors and the many changes made by vendors, any statement such
      as "this Unix is an SVR2" is at best a statistical statement
      (except for some SVRn ports).  Also many Unices offer most of
      both worlds (either mixed as in SunOS or strictly separated as in
      Apollo?).  So this section is perhaps not very useful...

      The list of features in previous sections can also help.  For
      example, if a system has a poll(2) but no select(2), it is highly
      probable that it is derived from SVR3.  Also the name of the OS
      can provide a clue, as well as the logon message (e.g.  SGI's
      "Irix SVR3.3.2") or the output of "uname -a" command.  Available
      commands can also provide hints but this is probably less
      reliable than kernel features.  For example, the type of terminal
      initialization (inittab or ttys) is a more reliable indicator
      than the print subsystem.

      Feature            Typical in SVRx          Typical in xBSD

      kernel name        /unix                    /vmunix
      terminal init      /etc/inittab             /etc/ttys (only getty to 4.3)
      boot init          /etc/rc.d directories    /etc/rc.* files
      mounted FSs        /etc/mnttab              /etc/mtab
      usual shell        sh, ksh                  csh, #! hack
      native FS          S5 (blk: 512-2K)         UFS (blk: 4K-8K)
                         file names <= 14 bytes   file names < 255 bytes
      groups             need newgrp(1)           automatic membership
                         SVR4: multiple groups
      print subsystem    lp, lpstat, cancel       lpr, lpq, lprm (lpd daemon) ??
      terminal control   termio, terminfo,        termios (sgtty before 4.3reno)
                         SVR4: termios (POSIX)    termcap
      job control        >= SVR4                  yes
      ps command         ps -ef                   ps -aux
      string fcns        memset, memcpy           bzero, bcopy
      process mapping    /proc  (SVR4)

6.6)  Brief notes on some well-known (commercial/PD) Unices.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      (I am not at all satisfied with this section, unfortunately I
      have neither the time nor the documents to make it much better
      (wrt contents).  Should only list Unices known by a reasonably
      wide audience.  Small and non-US Unices welcome, e.g. Eurix.  In
      need of reformatting)

      This section lists (in alphabetical order) some of the better
      known Unices along with a brief description of their nature.

      AIX:  IBM's Unix, based on SVR2 (later up to SVR3.2?) with varying
	 degrees of BSD extensions, for various hardwares.  Proprietary
	 system admin (SMIT).  Both 850 and Latin-1 CPs.  Quite
	 different from most Unices and among themselves.
	 Newsgroup: comp.unix.aix.
         - 1.x (for 386 PS/2)
         - 2.x (for PC RTs)
         - 3.x (for RS/6000), paging kernel, logical volume manager, i18n;
           3.2 adds TLI/STREAMS
         - there is also a version for S/370 mainframes (as task under VM)
         Was to have been base for OSF/1 until Mach was chosen instead.

      AOS (IBM):  4.3BSD port to IBM PC RT (for educational institutes).
         Don't confuse with DG's proprietary OS of same name.

      Arix:  SV

      A/UX (Apple): SV with Berkeley enhancements, NFS, Mac GUI.  System 6
         (later System 7) runs as guest of A/UX (opposite of MachTen).
	 Newsgroup: comp.unix.aux.
         - 2.0:  SVR2 with 4.2BSD, system 6 Mac applications.
         - 3.0 (1992): SVR2.2 with 4.3BSD, system 7 applications.

      BOS for Bull's DPX/2 (680x0)
         - V1 (1990): SVR3 with BSD extensions (FFS, select, sockets),
	   symmetric MP, X11R3
         - V2 (1991): adds job control, disk mirroring, C2 security,
	   DCE extensions

      386BSD: Jolitz's port of Net2 software.  Posix, 32-bit, still in alpha.

      BSD/386 (80386):  from BSDI, with source (augmented Net2 software)
         Newsgroup: comp.unix.bsd.

      Chorus/MiXV:  Unix SVR3.2 (SVR4) over Chorus nucleus, ABI/BCS.

      Coherent (80286):  Unix clone compatible with V7, some SVR2 (IPC).
         V4.0 is 32-bit.  Newsgroup: comp.os.coherent

      Consensys: SVR4

      CTIX: SV-based, from Convergent

      D-NIX:  SV

      DomainIX (Apollo):  dual Unix over Apollo Domain operating system

      DomainOS (Apollo):  BSD 4.2? with System V? (strict differentiation?)
         - 10.x

      DVIX (NT's DVS):  SVR2

      DYNIX (Sequent): 4.2BSD-based

      DYNIX/PTX: SVR3-based

      Esix (80386):  pure SVR4, X11, OpenLook (NeWS), Xview

      Eurix (80?86):  SVR3.2 (german?)

      FTX: Stratus fault-tolerant OS (68K or i860-i960 hardware)

      GNU Hurd (?):  vaporware from the Free Software Foundation (FSF):
	 Unix emulator over Mach 3.0 kernel.  Many GNU tools are very
	 popular (emacs) and used in the PD Unices.

      HP-UX (HP):  old from S III (SVRx), now SVR2 (4.2BSD?) with SV utilities
         (they have trouble making up their minds).
         - 6.5: SVR2
         - 7.0: SVR3.2, symlinks
         - 7.5
         - 8.0: BSD based? for HP-9000 CISC (300/400) and RISC (800/700)

      Interactive SVR3.2 (80x86): pure SVR3.  Interactive has been bought
         by Sun; will their system survive Solaris?

      Idris:  first Unix clone by Whitesmith.
         - 4D

      Irix (SGI):  SVR3.2, much BSD.  Newsgroup: comp.sys.sgi.

      Linux (80386):  PD Unix, SVish.  Available with sources.
         Newsgroup: comp.os.linux

      MachTen, Tenon Intersystems:  runs as a guest of System 6, no memory
         protection, 4.3BSD environment with TCP, NFS.

      MacMach (Mac II): 4.3BSD over Mach 3.0 microkernel, X11, Motif, GNU
         software, sources, experimental System 7 as Mach task.

      Mach386: from Mt Xinu.  Based on Mach 2.5, with 4.3BSD-Tahoe
         enhancements.  Also 2.6 MSD (Mach Source Distribution).

      Microport (80x86):  pure SVR4, X11, OpenLook GUI

      Minix (80x86, Atari, Amiga, Mac):  Unix clone compatible with V7.
         Sold with sources.  Being POSIXified (sp?).  Newsgroup: comp.os.minix.

      MipsOS:  SVish (RISC/OS, now dropped, was BSDish)

      more/BSD (VAX, HP 9000/300):  Mt Xinu's Unix, based on 4.3BSD-Tahoe.
         Newsgroup: comp.os.xinu?

      Net/2 tape (from Berkeley, 1991): BSD Unix, essentially compatible with
         4.3BSD, includes only sources free of AT&T code, no low-level code.
	 See 386BSD and BSD/386 above.

      NextStep (Next):  BSD over Mach kernel, own GUI.  386 version coming?
         - 1.0

      NEWS-OS (Sony)
         - 3.2

      OSF/1 (DEC): DEC's port of OSF/1

      PC-IX (IBM 8086):  SV

      SCO Xenix (80x86):

      SCO Unix (80x86):  SVR3.2

      Solaris (Sparc, 80386):
         - 1.0:  essentially same as SunOS 4.1.1, with OpenWindows 2.0 and
           DeskSet utilities.
         - 1.0.1:  SunOS 4.1.2 with multiprocessing (kernel not multithreaded);
           not for 386
         - 2.0:  will be based on SVR4 (and have symmetric MP), will include
           support for 386;  with OpenWindows 3.0 (X11R4), DeskSet, ONC, NIS.
           Compilers unbundled!

      SunOS (680x0, Sparc, i386):  based on 4.3BSD, includes much from System V.
         Main Sun achievements: NFS (1984), SunView (1985), NeWS
	 (1986, postscript imaging, now in OpenWindows), OpenLook GUI standard,
	 OpenWindows (NeWS, X11, SunView!).  Newsgroup: comp.sys.sun.*.
         - 3.x:  SV IPC package, FIFOs
         - 4.0.3: lightweight processes, new virtual mem, shared libs
         - 4.1: STREAMS & TLI, 8-bit clean?, async I/O, ms-dos file system
         (continues as Solaris -- see above).

      UHC (80x86): pure SVR4, X11, Motif

      Ultrix (DEC):  based on 4.2BSD with much of 4.3.
         Newsgroup: comp.unix.ultrix.
         - 3.1, 4.0

      UNICOS (Cray):  Newsgroup: comp.unix.cray
         - 5.x, 6,x, 7.0

      UTEK (Tektronix)
         - 4.0

      Xenix (80x86):  1st Unix on Intel hardware, based on SVR2 (previously on
         S III and even V7).  Newsgroup: comp.unix.xenix.

      3B1 (680x0): SV-based, done by Convergent for AT&T.
	 Newsgroup: comp.sys.3b1.

6.7)  Real-time Unices.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      This information is fragmentary.  I doubt all of following are Unices --
         input is welcome.

      RTU (Concurrent), for 68K boxes

      Stellix (Stardent); it's Unix, but is it real-time?

      Velocity (Ready Systems):

      VxWorks (Wind River Systems):  BSDish, no termcap.
         Newsgroup: comp.os.vxworks.

      pSOS??

6.8)  Unix glossary.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      This section provides short definitions of various concepts and
      components of (or related to) Unix systems.

      Chorus: message-passing microkernel, may form basis for a future release
         of SV.  Chorus already have SVR4 running on top (binary-compatible).

      DCE (Distributed Computing Environment, from OSF): Includes RPC (Apollo's
         NCS), directory service (local based on DNS, global on X.500), time,
         security, and threads services, DFS (distrib. file system), ....
         OS-independent.

      DME (Distributed Management Environment, from OSF):  future.

      FFS (Fast File System): alias for UFS (BSD name)

      Mach: modern kernels from CMU (Carnegie Mellon University) on which many
         Unices and other OSs are based (e.g. OSF/1, MacMach, ...):
         - 2.5: monolithic kernel with 4.2BSD
         - 3.0: microkernel with BSD Unix server in user space (and other OSs,
	   e.g. MS-DOS)
         Newsgroup: comp.os.mach

      MFS: Memory File System

      NFS (Network File System):  contributed by Sun to BSD, stateless server

      ONC (Open Network Computing): from Sun(?), includes RPC, name service
	 (NIS aka YP), NFS, ... (found in many Unices, other OSs).

      RFS (Remote File System):  SV, stateful server, incompatible with NFS

      RPC (Remote Procedure Call): high-level IPC (inter-process communication)
         mechanism.  Two flavors.
         - ONC: Over TCP or UDP (later OSI), uses XDR to encode data.
         - DCE: has a different RPC mechanism (based on Apollo's NCS)

      S5 FS:  System V's native file system, blocks 512 to 2K.

      sockets:  BSD interface mechanism to networks (compare TLI).

      STREAMS:  a message-passing kernel mechanism, initially in SVR3, which
         provides a very good interface for protocol development.

      TLI (Transport Library Interface):  SV's interface to transport services
         (TCP, OSI).  UI has also defined an APLI (ACSE/Presentation Library
         Interface)

      UFS (?):  BSD's native file system, blocks 4K to 8K, cylinder groups,
         fragments.

      XTI (X/Open Transport Interface):  TLI with enhancements

6.9)  Acknowledgements.

      From: "Pierre (P.) Lewis" <lew@bnr.ca>
      Date: Sun, 11 Oct 1992 15:29:00 +0000
      Version: 2.0

      (in addition to references): pat@bnr.ca, guy@auspex.com,
      pen@lysator.liu.se, mikes@ingres.com, mjd@saul.cis.upenn.edu,
      root%candle.uucp@ls.com, ee@atbull.bull.co.at,
      Aaron_Dailey@stortek.com.  Many thanks!
Xref: sparky comp.unix.questions:16003 comp.unix.internals:2172