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Date: Sat, 6-Aug-83 22:02:53 EDT
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                          UNIX* System V and 4.1C BSD

                                 John Chambers

                  Office of Academic Computing & Biostatistics
                 University of Texas Medical Branch, Galveston

                                John Quarterman

                               Computation Center
                         University of Texas at Austin


            Presented at the July 1983 USENIX Conference in Toronto.
          cO Copyright 1983 by the Regents of the University of Texas.


               This paper compares System V  (the  UNIX  system  which
          Western Electric is currently licensing) and 4.1C BSD   (the
          final   precursor   to  4.2BSD,  the  research  UNIX  system
          developed for DARPA  by  the  University  of  California  at
          Berkeley),  based  on  experience with both systems on a DEC

               The  comparison  covers  several  areas  and   includes
          comments  organized  by  manual section on numerous specific
          features (languages, shells, text  editing  and  formatting,
          devices,  etc.),  plus more general and detailed discussions
          of such topics as: installation and  configuration;  sources
          and  documentation;  groups  and  identifiers; file systems;
          interprocess    communications;    networks;     performance
          (including some tentative benchmarks); and vendor support.

               Common features are mostly  left  to  the  manuals,  in
          order  to  better concentrate on differences.  This is meant
          to be a qualitative comparison, intended to serve only as  a
          guide for further study.


            * UNIX is a Trademark of Bell Telephone Laboratories, Inc.



           1.  Introduction.......................................   2
               1.1   Intent.......................................   2
               1.2   Format of the Paper..........................   2
               1.3   Disclaimers and Acknowledgments..............   3

           2.  Manual Sections....................................   3
               2.1   Commands.....................................   3
                     2.1.1   User convenience.....................   3
                     2.1.2   Programming support environments.....   4
                     2.1.3   Shells...............................   6
                     2.1.4   Formatting and typesetting...........   6
                     2.1.5   Graphics.............................   7
                     2.1.6   Ingres...............................   7
                     2.1.7   Text editors.........................   7
                     2.1.8   Electronic mail......................   8
                     2.1.9   Printing.............................   8
               2.2   System Calls.................................   9
                     2.2.1   Vfork and fork.......................   9
                     2.2.2   Reboot...............................   9
                     2.2.3   Setpgrp..............................  10
                     2.2.4   Group system calls...................  10
                     2.2.5   Ioctls...............................  10
                     2.2.6   Open and fcntl.......................  10
                     2.2.7   4.1C BSD file system calls...........  11
                     2.2.8   Timing...............................  12
                     2.2.9   IPC..................................  12
               2.3   Libraries and Subroutines....................  12
                     2.3.1   Common Object File Format
                             routines.............................  12
                     2.3.2   Utmp routines........................  12
                     2.3.3   F77 library..........................  12
                     2.3.4   Knuth algorithms.....................  12
                     2.3.5   Software signals and matherr.........  13
                     2.3.6   Stdio buffering......................  13
                     2.3.7   Printf...............................  13
                     2.3.8   String routines......................  14
                     2.3.9   Network library......................  14
               2.4   Devices......................................  14
                     2.4.1   Tty..................................  14
                     2.4.2   DH-11................................  14
                     2.4.3   KMC-11B..............................  15
                     2.4.4   VPM..................................  15
                     2.4.5   Synchronous terminal.................  15
                     2.4.6   BLIT.................................  15
                     2.4.7   Ptys.................................  15
                     2.4.8   Generalized disk driver..............  15
                     2.4.9   Generalized tape driver..............  16
               2.5   File Formats.................................  16

                                     - i -

                     2.5.1   A.out................................  16
                     2.5.2   Ar...................................  16
                     2.5.3   Fs...................................  17
                     2.5.4   Termcap and descendants..............  17
               2.6   Games........................................  17
                     2.6.1   System V games.......................  17
                     2.6.2   4.1C BSD ASCII graphics games........  17
                     2.6.3   PDP-11 compatibility.................  18
               2.7   Miscellany...................................  18
                     2.7.1   File system hierarchy................  18
               2.8   Maintenance..................................  18
                     2.8.1   Init, getty, and login...............  18
                     2.8.2   Shutdown, halt, and reboot...........  19
                     2.8.3   Backups..............................  19
                     2.8.4   Fsck, fsdb, etc......................  20
                     2.8.5   Monitoring and debugging.............  20
                     2.8.6   Accounting...........................  21

           3.  Installation and Configuration.....................  21
               3.1   Installation.................................  21
               3.2   Configuration................................  22
               3.3   Transition...................................  23

           4.  Sources and Documentation..........................  23
               4.1   Make.........................................  24
               4.2   SCCS.........................................  24
               4.3   Sources......................................  24
               4.4   Documentation................................  25

           5.  Groups and Identifiers.............................  25
               5.1   Groups.......................................  25
               5.2   Identifiers..................................  26

           6.  File Systems.......................................  26
               6.1   System V.....................................  27
                     6.1.1   New file system block size...........  27
                     6.1.2   Faster access........................  27
               6.2   4.1C BSD.....................................  27
                     6.2.1   Reimplementation for efficiency......  27
                     6.2.2   Other modifications..................  28
                     6.2.3   Extended (network) file system.......  28

           7.  Interprocess Communications (IPC)..................  29
               7.1   System V.....................................  29
               7.2   4.1C BSD.....................................  29

           8.  Networks...........................................  30
               8.1   System V.....................................  30
                     8.1.1   X.25.................................  30
                     8.1.2   PCL network..........................  30
                     8.1.3   NSC network..........................  30

                                     - ii -

                     8.1.4   RJE to IBM...........................  31
               8.2   4.1C BSD.....................................  31
                     8.2.1   General networking framework.........  31
                     8.2.2   Variety of hardware and protocols
                             supported............................  31
                     8.2.3   Internet (TCP/IP)....................  32
                     8.2.4   Berkeley protocols...................  32
               8.3   UUCP.........................................  32
               8.4   USENET.......................................  33

           9.  Performance........................................  33
               9.1   Some Qualitative Remarks.....................  33
                     9.1.1   Paging vs. swapping..................  33
                     9.1.2   Terminal I/O.........................  34
               9.2   Tentative Benchmarks.........................  34
                     9.2.1   Load simulation......................  35
                     9.2.2   File system throughput...............  36

          10.  Vendor Support.....................................  36
               10.1  Western Electric.............................  36
               10.2  U.C. Berkeley................................  36
               10.3  DEC..........................................  36
               10.4  Third Parties................................  37
                     10.4.1  OEMs.................................  37
                     10.4.2  Emulations...........................  37
                     10.4.3  Consultants..........................  37
                     10.4.4  Authors..............................  38

          11.  Conclusion.........................................  38
               11.1  Selection Criteria...........................  38
               11.2  Combinations.................................  38
               11.3  Future Directions............................  39
                     11.3.1  UNIX standards committee.............  39
                     11.3.2  Berkeley features and Bell...........  39
                     11.3.3  Bell licensing and Berkeley..........  39
               Appendix A:  Terminology...........................  39
               Appendix B:  Load Simulation Job...................  41

                                    - iii -

                          UNIX* System V and 4.1C BSD

                                 John Chambers

                  Office of Academic Computing & Biostatistics
                 University of Texas Medical Branch, Galveston

                                John Quarterman

                               Computation Center
                         University of Texas at Austin


            Presented at the July 1983 USENIX Conference in Toronto.
          cO Copyright 1983 by the Regents of the University of Texas.


               This paper compares System V1 (the  UNIX  system  which
          Western Electric is currently licensing) and 4.1C BSD2  (the
          final   precursor   to  4.2BSD,  the  research  UNIX  system
          developed for DARPA3 by  the  University  of  California  at
          Berkeley),  based  on  experience with both systems on a DEC

               The  comparison  covers  several  areas  and   includes
          comments  organized  by  manual section on numerous specific
          features (languages, shells, text  editing  and  formatting,
          devices,  etc.),  plus more general and detailed discussions


            * UNIX is a Trademark of Bell Telephone Laboratories, Inc.

           1. See Appendix A for the official names of Bell UNIX

           2. See Appendix A for details about Berkeley Software
              Distributions (BSD).

           3. Defense Advanced Research Projects Agency (DARPA),
              formerly ARPA.

           4. VAX, PDP, UNIBUS, MASSBUS, and SBI are Trademarks of
              Digital Equipment Corporation (DEC).

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Subject: Compare.B
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Date: Sat, 6-Aug-83 22:03:24 EDT
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                                     - 2 -

          of such topics as: installation and  configuration;  sources
          and  documentation;  groups  and  identifiers; file systems;
          interprocess    communications;    networks;     performance
          (including some tentative benchmarks); and vendor support.

               Common features are mostly  left  to  the  manuals,  in
          order  to  better concentrate on differences.  This is meant
          to be a qualitative comparison, intended to serve only as  a
          guide for further study.

          1.  Introduction

          1.1  Intent

               This  paper  describes  certain   differences   between
          System V  and  4.1C BSD, leaving details of common functions
          to the manuals.  This is a qualitative comparison,  intended
          to serve only as a guide for further study.

               While performance is not a major theme of  this  paper,
          some  tentative  benchmarks  are  included  to  indicate the
          relative performance of the two systems.   These  benchmarks
          should  not  be considered conclusive, since 4.1C is not 4.2
          and since we have not had sufficient  production  experience
          with System V.

               This  paper  supersedes  a   previous   paper,   ``UNIX
          System III and 4.1BSD, A Practical Comparison'', by the same
          authors.  In some cases, features are noted herein as having
          been  introduced  in  System V  or  4.1C BSD  when they were
          actually introduced in System III or 4.1BSD.   This  usually
          occurs  when  comparisons  are being made with V7/32V and is
          done simply to decrease the verbiage.

          1.2  Format of the Paper

               The first section following the  Introduction  contains
          subsections   corresponding   to   sections   of   the  UNIX
          Programmer's Manual* in order to  provide  a  framework  for
          comparison of detailed features of the operating systems.

               There follow several sections  on  subjects  which  are
          wider  than  a  single  manual  entry  or  which we consider


            * The 4.1C BSD title; see section on Documentation.

                                     - 3 -

               Finally, there is a summary section which includes some
          comments on recent cooperation among UNIX system developers.

          1.3  Disclaimers and Acknowledgments

               The authors of this paper are in no way affiliated with
          the  University of California, Bell Laboratories, or Western
          Electric,  and  are  solely  responsible  for  the  opinions
          presented herein.

               4.1C BSD   is   not   a   regular   Berkeley   Software
          Distribution  and  inquiries  should not be sent to Berkeley
          concerning  it.   Facilities  in  4.1C  may  be  represented
          differently  in  4.2.   In  cases  in which we know what the
          differences will be we have noted them but we do  not  claim
          to  have  caught  every  case.   When  Berkeley  is ready to
          distribute 4.2BSD, they will announce it.

               We would like to acknowledge Dr. Michael Molloy of  the
          Computer  Science Department, University of Texas at Austin,
          for the use of  the  departmental  VAX-11/780  and  for  his
          assistance,   as  well  as  Bill  Lee  of  the  U.T.  Austin
          Computation Center for  his  continued  moral  and  material
          support.   We  would  also  like  to thank the following for
          reviewing the  paper:  Sam  Leffler  of  the  University  of
          California  at  Berkeley,  Nina McCloskey of AT&T Technology
          and  Licensing  Division,  Armando  Stettner  of  DEC,   Dan
          Franklin  of  Bolt, Beranek, and Newman (BBN), and Doug Gwyn
          of the U.S. Army Ballistic Research Laboratory (BRL).

          2.  Manual Sections

               The subsections of this section  generally  follow  the
          order of the UNIX Programmer's Manual.

          2.1  Commands

               The general utility  commands  supplied  with  the  two
          systems  exhibit  relatively  minor  differences,  mainly in
          terms of the options available.  A few commands are included
          in  each  distribution which do not occur in the other; many
          of these are  of  questionable  usefulness  anyway  and  the
          reader  is  referred  to  the  manuals  for further details.
          Certain larger packages, however, such as  language  support
          facilities,  are  rather  different and are discussed in the
          following sections.

          2.1.1  User convenience  Several  utilities  are  considered
          important for the convenience of the frequent user.

                                     - 4 -

               Berkeley UNIX provides the page and more  file  perusal
          commands,  used  to examine a file a screenful at a time. No
          equivalent is available in Bell UNIX.

               The Berkeley ls command understands proper  multicolumn
          formatting  of  a  directory listing (when stdout is a tty).
          Under System V, ls generates a listing with  one  entry  per
          line;  a  multicolumn listing must be obtained by piping the
          output into the paste command, e.g.

                              ls | paste - - - - -

               The Berkeley w program may  be  used  to  monitor  user
          activity;  the  System V  equivalent  uses  a  command file,
          /etc/whodo, to generate similar information. However, it  is
          rather inconvenient to have to specify the absolute pathname
          and few users actually have /etc as part  of  their  default
          path.   (We  note,  of  course,  that  the  superuser's PATH
          environment variable does include /etc, perhaps  to  suggest
          that  only  system  administrators  and  the  like should be
          interested in such information.)

          2.1.2  Programming support environments    Several   changes
          have  been  made  to  the  C programming support environment
          (Software Generation System in WECo parlance) in System V.

               Most of the #include files  have  been  rearranged  and
          expanded,  and  it is advisable to recompile all C programs.
          Pcc,  the   portable   C   compiler,   includes   reasonable
          enumerations,   changes  to  structure  and  union  handling
          (nonunique structure member names), correct handling of  the
          void  data  type,  and  several  bug  fixes.  The cc command
          itself  has  added  the  W  flag  to  allow  options  to  be
          explicitly  specified  for a particular compilation subpass.
          Certain bugs which are known to remain are documented in the
          System Release Description.

               Two new tools  are  included:  cxref,  which  generates
          cross-reference  listings  and obsoletes both cref and xref,
          and cflow, which  builds  a  graph  of  external  references
          occurring  in  a  collection  of  assorted  source files (C,
          assembler, etc.).

               The System V f77 programming support  environment  also
          includes  two  new  tools:  asa  interprets the standard ASA
          carriage control characters, and fsplit may be used to split
          FORTRAN  sources  (f77, efl, ratfor) on a procedure-per-file
          basis.  In addition, the load-time library has been  greatly
          extended and enhanced.

                                     - 5 -

               The libraries for both  C  and  f77  are  available  in
          profiled  versions, which must be loaded explicitly in place
          of the default, non-profiled ones.  These profiled libraries
          allow  program  execution  profiling at the library function
          level rather than the user program function level.

               Further,  the  symbolic  debugger  sdb  is  very   much
          improved  and  may  be  used  easily  with  either  C or f77

               The as assembler and ld linker have  been  modified  to
          utilize   the  new  Common  Object  File  Format,  which  is
          discussed below.  Note that any change to a source file  for
          a  program  thus  necessitates  recompilation of all sources
          before the objects may be relinked using ld, since  the  old
          and new object formats are radically different.

               The C compiler in 4.1C (pcc) is very similar to the one
          in  System III,  including  void, union, enum, and structure
          elements named per structure, some of which were added after
          32V.   Berkeley added very long identifiers in 4.1BSD, while
          System III and  System V  retained  the  old  7/8  character
          identifiers.    The   as   assembler,  the  ld  linker,  and
          associated  libraries  are  similar  to  the  ones  in  32V,
          although  in  4.1  ld  was reworked to be four to five times
          faster and this improvement is preserved in  4.1C  and  4.2.
          The dbx symbolic debugger is new.

               4.1C BSD has some bug fixes and other  improvements  to
          f77  (an  overlaid version of this compiler is available for

               4.2 has an extensively reworked version of f77 and  its
          associated  libraries:   early  versions of this new FORTRAN
          package were apparently the  source  for  the  new  System V
          FORTRAN facilities.

               Both systems support Ratfor and  the  Extended  FORTRAN
          Language  (EFL),  but  4.1C additionally provides the struct
          utility, used to convert  FORTRAN  sources  into  reasonably
          clean Ratfor.

               System V has bs, essentially derived from BASIC.  There
          is  no  equivalent  in  4.1C BSD; however, the University of
          British Columbia BASIC sytem is compatible with 4BSD.

               Similarly, System V includes  the  classic  sno  SNOBOL
          system, while 4.1C includes PASCAL, FRANZ LISP, APL, and fp.
          APL is a user contributed software package from Purdue.   Fp
          (Functional   Programming   language   compiler/interpreter)
          implements the applicative language proposed by John  Backus

                                     - 6 -

          in  his  Turing award lecture.  4.2 may include Icon as user
          contributed software.

               There is a COBOL compiler  commercially  available  for
          4BSD, and possibly for System V.

          2.1.3  Shells  System V supports the Bourne shell (sh), with
          few  noticeable changes from V7.  4.1C BSD has much the same
          Bourne shell plus the Cshell (csh), often a new user's first
          command language.

               The Cshell has most of the capabilities of  the  Bourne
          shell  (though  the  syntax is different), plus the history,
          alias and directory stack features.  History and alias allow
          editing  and replaying of saved commands.  Such features are
          the main reason many users prefer the Cshell (although  some
          cite  its  extensive  C-like  control  structures as another

               The 4.1C Cshell also has a set of job control  features
          (requiring  the  Berkeley  `new  tty' terminal driver) which
          allow the user to suspend and resume subprocesses.

               The 4.1C resource limitation  facilities  are  normally
          accessed   via  the  csh  limit  command.   The  only  close
          equivalent in System V sh is the  ulimit  command,  used  to
          control the size of the file a child process may write.

          2.1.4  Formatting and typesetting  4.1C offers the -me macro
          package,  while  System V  has  the  -mm  package,  somewhat
          augmented from PWB.  The -ms macros have been  removed  from
          System V  but  are  still  found in 4.1C.  In 4.2, they have
          been extended to provide support for tables of contents  and
          the like.

               System V  includes   additional   macro   support   for
          generating slides and viewgraphs.

               An improved interface to the Versatec  is  provided  in
          System V, along with new ioctl calls for state control.  The
          vcat filter for troff which was  documented  but  absent  in
          System III seems to have disappeared entirely in System V.

               Both systems have Versatec drivers expecting  a  single
          interrupt  address,  whereas  the  Versatec  itself  has two
          configured into the hardware.  4.1C at least has comments in
          the code to tell you this (and #ifdefs to deal with it).

               The 4.1 Versatec user programs  expected  a  unit  wide
          enough  to  handle four pages abreast; this problem has been
          fixed in 4.2 (but not 4.1C) by  extensions  to  the  printer

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                                     - 7 -

          spooling facility.

               The Berkeley font library seems rather  more  extensive
          than  that  provided with System V.  These fonts are used by
          the Versatec filters to simulate  the  mounted  fonts  of  a
          C/A/T  phototypesetter,  the standard destination device for
          non-device independent troff.

               The best version of troff comes with neither  of  these
          systems.  This is the Typesetter Independent Troff (TITroff)
          package (commonly known as DITroff, for  Device  Independent
          Troff).   It  is  available separately from Western Electric
          and includes useful graphics packages (pic and ideal)  which
          can be used to augment the basic typesetting facilities.

               In 4.2, the printer spooling facilities have hooks  for
          TITroff  so  that  the  package can be used immediately when
          obtained  (though  TITroff  itself  is   still   distributed
          separately by Western Electric).  See below under Printing.

               The Writer's Workbench facilities  style,  diction  and
          explain,   which   analyze   surface   characteristics   and
          readability of written text, are supplied with  4.1C.   This
          is apparently a Bell Research Group package and is available
          separately from Western Electric.  Style ignores macros from
          -ms,  -me,  -mm,  and  -ma,  although  the  manual page only
          mentions -ms and -mm.

               4.2 also includes an improved refer and bib.

          2.1.5  Graphics   4.1C  has  rather   rudimentary   graphics

               In contrast, System V has  the  PWB  graphics  package,
          including   ged,  a  graphical  editor,  and  numerous  data
          generation,  transformation,  and  display  commands.   This
          graphics capability has been used extensively in conjunction
          with the accounting packages.

          2.1.6  Ingres  The relational database system Ingres is part
          of 4.1C, and a commercial version of Ingres is available for
          4BSD.  We do not know if it will work under System V.

          2.1.7  Text editors  Both systems have the traditional  UNIX
          editor,  ed,  and  System V  has  adopted  the  Berkeley  vi
          (screen) and ex (line) editors, which are also of course  in

               System V documents a new screen editor named se but  it
          was  not  included  on the distribution.  Apparently it does
          not utilize the terminal independence capability provided by

                                     - 8 -

          termcap but, rather, uses its own terminal description file,
          /usr/lib/se.term (also not on the distribution).

               Recent versions of the Rand Editor e and UNIX Emacs can
          presumably  be  made  to run correctly on System V, although
          this was not our experience.

               Though the distributed versions  of  the  two  commonly
          available  versions  of Emacs have problems running on 4.1C,
          since they  still  attempt  to  use  the  obsolete  MPX  IPC
          facility,  at least one (Gosling's) has already been adapted
          at Berkeley to use the superior Berkeley IPC mechanism.  (No
          problems were noted running them under 4.1.)

          2.1.8  Electronic mail   System V  has  a  rudimentary  mail
          system, not much altered from V7 or System III.

               4.1C has  a  more  elaborate  one,  with  most  of  the
          commonly  useful mail functions.  4.1C actually provides two
          mail  delivery  routes,  one  unprotected  and   the   other
          encrypted.   There  is  a  new  mail delivery program called
          sendmail (a descendant of  the  delivermail  of  4.1)  which
          provides  a  central mail handling system capable of dealing
          with multiple networks and addressing formats.

               The Rand mh system can be used as an alternative  front
          end  to  the  Berkeley mail system and will be provided with
          4.2 as user contributed software.  Some people use Emacs for
          this purpose.

               We understand  that  the  MMDF  mail  system  from  the
          University  of  Maryland can be used with either the Bell or
          the Berkeley version of the  Unix  System  but  we  have  no
          direct experience with it.

          2.1.9  Printing  The lpr command and lpd  daemon  have  been
          modified  in  4.1C to use the file /etc/printcap (similar to
          /etc/termcap) to define the characteristics of  the  various
          printers  attached  to  a  system.  Printers may be added or
          deleted without changing  the  programs  and  output  filter
          programs  are  supported  on  a  per-device  basis.   It  is
          possible to treat a printer on another machine as if it were
          local  (from  the  user's viewpoint) and have lpd ship files
          across a network to it.  The Berkeley IPC mechanism is  used
          for  queueing  requests, editing the queue, monitoring queue
          activity, etc.

               In 4.2, lpr, etc., provide support for  various  raster
          devices  (such  as Varian or Versatec), laser printers (such
          as Imagen), and numerous ordinary  printers.   Specifying  a
          new type of device in /etc/printcap is relatively easy.

                                     - 9 -

               The user specifies a printer either as a  command  line
          option to lpr or in the PRINTER environment variable.

               The System V lpr is considered obsolete  and  has  been
          replaced  by  a  spooling  system  similar in flavor to that
          provided  with  4.1C  but  without  the  extensive   network
          support.   The  LP-11  is  still  considered  the  canonical
          printing device, although a particular  destination  may  be
          specified by the LPDEST environment variable.

               MDQS (Multiple Device  Queueing  System)  is  available
          from  BRL  and  provides  support  for  queueing output to a
          variety of different devices.

          2.2  System Calls

               The user interface to most of the system calls  is  the
          same, i.e., the interface routines in the C library have the
          same calling sequence, but the actual  system  call  numbers

               4.1C has introduced a number of new system calls,  some
          intended  to eventually replace older ones completely.  Many
          of the older ones are now simulated  by  interface  routines
          that call the new, extended ones.

          2.2.1  Vfork and fork  The fork system call in System V  has
          been  changed  to  require only one pass through the process
          table per invocation. A resulting improvement in performance
          is claimed; however, we did not attempt to measure this.

               4BSD includes the vfork  version  of  the  fork  system
          call,  which  allows  creation  of a new process without the
          need for copying the entire address  space  of  the  parent.
          This makes sense in any environment where processes get very
          large, as in the paging environment provided  by  4.1C  (see
          comments below), but the implementation also imposes certain
          restrictions which  can  mislead  the  unwary.   Performance
          statistics relating to the use of vfork are widely available
          and are outside the domain of this presentation.

               2.9BSD has vfork for the PDP-11.  4.3BSD will eliminate
          the need for vfork by a reimplementation of fork.

          2.2.2  Reboot  4.1C has the reboot  system  call,  which  is
          quite  convenient  for persons engaged in system development
          work.  (See below on the reboot command.)

               System V documents a reboot system call  for  the  WECo
          3B20S but nothing seems to be available for DEC machines.

                                     - 10 -

          2.2.3  Setpgrp  4.1C has elaborated the setpgrp system  call
          to  be more compatible with the job control functions of the

          2.2.4  Group system calls  4.1C has a new method of  dealing
          with  the  concept  of  groups  and group ids (see the major
          section below on Groups).

          2.2.5  Ioctls   The  ioctl  system   call   is   essentially
          identical  in  the two systems.  The interesting differences
          are in the terminal driver ioctls.  Both drivers utilize the
          ``line  discipline''  notion,  allowing dynamic choice among
          several protocols by the user process.

               Berkeley offers several new features in  4.1C BSD  over
          the V7 terminal driver.  Some of these are accessed as a new
          line discipline (the ``new tty'' discipline),  while  a  few
          others  are implemented as additional ioctl calls.  There is
          a line discipline in 4.1C  for  an  RS232  interface  to  an
          Hitachi  tablet  (this  is  undocumented).  All of these are
          useful features, but the tty  ioctls  have  become  somewhat

               The System V terminal  driver  is  radically  different
          from  the  V7  one.  Many functions which always should have
          been orthogonal now are. As one example, the  conversion  of
          carriage  return  to  new  line  on input and of new line to
          carriage return and line feed on output are  now  separately
          controllable   functions.    Of   course,   this  driver  is
          hopelessly  incompatible  with  any  previous  one   (except
          System III)  and with the Berkeley one.  Additionally, there
          is peripheral processor support for this line discipline  in
          the KMC-11B (see below).

               System V also provides support for a  virtual  terminal
          protocol,  allowing  drivers  for  selected  terminals to be
          compiled directly into the kernel. The terminal type may  be
          manipulated by two related ioctls, LDSETT and LDGETT; a type
          specifier may then be passed to,  say,  getty  (see  below).
          Unfortunately, this feature is not well-documented and it is
          particularly advisable to study the terminal driver code and
          the file /usr/include/termio.h.

          2.2.6  Open and fcntl  The  open  system  call  in  System V
          presents essentially the same interface as in System III but
          now claims substantially improved performace due to the  use
          of a hashed inode table.

               The _dup2 function of V7 and 4BSD has been replaced  and
          elaborated  upon in System V by the fcntl system call.  4.1C
          preserves the 32V FIOEXCL ioctl call to  give  control  over

                                     - 11 -

          the  inheritance of file descriptors across an exec; this is
          provided by fcntl in Systems III and V.  In conjunction with
          an additional argument (mode) to the open system call, fcntl
          permits  access   to   the   O_NDELAY   (non-blocking   I/O)
          capability.   (The  System III  O_NDELAY  bug  appears to be
          fixed in System V.)

               4.1C uses an ioctl to set up non-blocking I/O but  also
          has various open modes in addition to the old read and write
          modes, plus the optional third argument for  some  of  them.
          Non-blocking opens, for instance, are supported.

               4.2  has  adopted  exactly  the  same  open  and  fcntl
          interfaces  as  System V,  even going so far as to duplicate
          the names of the mode bits.  A  different  include  file  is
          used for open, however.

          2.2.7  4.1C BSD file system calls  4.1C has a number of  new
          system   calls  affecting  file  I/O,  in  addition  to  the
          modifications to the open call noted above.

               There are  now  system  calls  for  mkdir,  rmdir,  and

               Equivalents of old calls that apply to file descriptors
          instead of file names have been added:  fchown and fchmod.

               Symbolic links require  some  specific  calls:   lstat,
          symlink, readlink.

               File truncation is supported by truncate and ftruncate,
          and file locking by flock.

               Scatter/gather I/O is supported by readv and writev.

               The notion of ``file descriptor'' has been  generalized
          to  include  various  other  kinds  of  descriptors, such as
          socket descriptors for use with IPC endpoints.  Many of  the
          system  calls,  e.g.  close,  that apply to file descriptors
          also have meaning with other types of descriptors, and there
          are  several new system calls to deal with descriptors, such
          as getdtablesize.  The most  generally  useful  of  the  new
          descriptor  system  calls  is  select,  which  is used to do
          synchronous multiplexing of operations by determining (among
          other  things)  whether it is possible to read or write data
          on any of a set of descriptors.

               See also the major sections below on File  Systems  and

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                                     - 12 -

          2.2.8  Timing  In 4.1C, all times are returned in a  machine
          independent  format,  viz., seconds and microseconds.  There
          is  also  improved  timezone   flexibility.    (Systems   in
          Australia   and   Europe   should   no   longer   experience
          difficulties with timezones.)

               4.1C uses a simulated 100 Hertz line  clock  to  report
          times  more  accurately than before.  The new system call to
          replace ftime and time is  called  gettimeofday.   Profiling
          using prof is also affected.

               The getitimer and setitimer system calls allow the  use
          of three interval timers, one for real time, one for virtual
          time (i.e., the time the process is actually  running),  and
          one  for  user  and  system virtual time.  The latter allows
          interpreters to be profiled, that is, keeping track of  when
          the  interpreted  program,  rather  than the interpreter, is
          running.  These timers had a bug in 4.1C, but work  properly
          in 4.2.

          2.2.9  IPC  The old MPX and FIFO IPC  mechanisms  have  been
          largely  superseded by the new mechanisms discussed below in
          the section on IPC.

          2.3  Libraries and Subroutines

               There are many changes in this section.

          2.3.1  Common Object File Format routines  System V  adds  a
          number of routines to provide specialized open, close, seek,
          and read operations for files written in the  Common  Object
          File Format (see below).

          2.3.2  Utmp routines  In accordance with substantial changes
          to the format of the utmp structure (see below) in System V,
          a collection of  routines  similar  to  those  provided  for
          manipulating  the password file have been added to deal with
          the /etc/utmp and /etc/wtmp files.

          2.3.3  F77 library   See  above  under  Programming  support
          environments for f77.

          2.3.4  Knuth algorithms  In addition to  the  binary  search
          (bsearch)  and  linear search (lsearch) algorithms available
          in System III, System V provides routines for searching hash
          tables (hsearch) and binary trees (tsearch).

               A related  UNIX-specific  utility,  ftw,  provides  the
          ability  to recursively descend a directory tree, applying a
          user-supplied function at each node.  (In other words, it is
          the subroutine equivalent of the find command.)

                                     - 13 -

          2.3.5  Software signals and matherr  System V preserves  the
          ssignal   (and   the   associated   gsignal)  facility  from
          System III, allowing  the  user  to  raise  and  dispose  of
          software signals.

               A  related  topic  is  the  inclusion  in  System V  of
          matherr,  an  error-handler invoked by functions in the math
          library.  The user may supply his own version of matherr  to
          control the disposition of such errors.

               4.1C preserves the software signals  added  in  4.1  to
          support  the  job  control features of the Cshell; these are
          related to the ``new tty'' line discipline.  (4.2 provides a
          new signal interface.)

          2.3.6  Stdio buffering  4.1C  buffers  output  even  if  the
          output  file is a terminal, but flushes all terminal or pipe
          output when the process attempts to read from a terminal  or
          a  pipe.  4.1C adapts its buffer size according to the block
          size of the file system containing the  relevant  files,  to
          produce a marked speed improvement.

               The System V stdio buffers have been increased and  the
          string-oriented   output  functions  have  been  changed  to
          provide  pseudo-line  buffered  output   to   terminals   if
          buffering  has  not  been specified explicitly.  As in 4.1C,
          output is flushed on terminal reads.

               Both systems  keep  stderr  unbuffered.   (The  calling
          program may, of course, determine the buffering via setbuf.)

               In 4.2 perror does a  single  write  (using  writev  to
          gather  the  arguments)  to alleviate the problem of single-
          character network transfers, but stderr is still unbuffered.

          2.3.7  Printf    System V   has   dropped   the   System III
          (undocumented)   vprintf  and  vfprintf,  retaining  the  V7
          (undocumented) doprnt routine, such  as  is  still  used  in
          4.1C.   The  old (undocumented) %r format has apparently not
          been restored, however.

               In a similar vein,  certain  Berkeley  programs  assume
          that   sprintf   returns  the  address  of  the  buffer,  an
          undocumented feature that  has  been  changed  and  properly
          documented  in System V (the number of characters written is

               System V printf follows the System III standard,  which
          abolished  the  old  capital letter formats ("%X", "%F") for
          long variables in favor of the prepended-`l' ("%lx",  "%lf")
          format   so   that  capital  letters  can  be  used  in  the

                                     - 14 -

          hexadecimal and  floating  point  formats  to  mean  capital
          letters in the output stream.

               4.1C has basically the V7 printf and scanf.

               The printf  and  scanf  formats  are  still  not  fully
          compatible in either system.

          2.3.8  String routines  As in System III,  System V  changes
          the  V7  (and 4BSD) index and rindex functions to strchr and
          strrchr, respectively, as well as adding  a  few  additional
          string   routines  reminiscent  of  certain  SNOBOL  pattern

               System V also provides new routines  to  perform  basic
          memory-to-memory  operations  (copy, compare, etc.) based on
          byte count rather than a terminating null character.

               4.1C provides the same functions via  the  bcopy  bcmp,
          and  bzero  routines, which are now in the C library as well
          as the kernel.

          2.3.9  Network library   The  4.1C  C  library  contains   a
          collection  of routines used for translating network-related
          names and numbers, such as gethostbyname,  which  takes  the
          name  of  a  host and returns its address.  There are also a
          few routines for manipulating  the  byte  order  of  network
          addresses,  such  as  htonl,  which  converts a network host
          address from network to host byte order, and  some  routines
          brought  up  from  the kernel that are used for manipulating
          byte arrays, such as bzero, which clears a byte array.

          2.4  Devices

               Details of device drivers are beyond the scope of  this
          paper.   We  only  mention  a  few corresponding to the most
          important devices.

          2.4.1  Tty  See above under ioctl for a  discussion  of  the
          terminal driver changes.

          2.4.2  DH-11  System V provides no  support  for  the  DH-11
          terminal  controller.   Although DEC no longer supports this
          device, many installations  either  still  own  DEC  DHs  or
          emulations  from  other vendors.  Also, DEC now supports the
          Emulex DH-11  emulation  (CS21/H).   The  replacement  is  a
          combination   of   DZ-11s   controlled   by  KMC-11Bs.   The
          System III dh driver is probably portable to  System V,  but
          of course you must acquire a System III distribution.

                                     - 15 -

          2.4.3  KMC-11B  System V  no  longer  supports  the  KMC-11A

               The KMC-11B may be used in conjunction with DZ-11s  for
          offloading  terminal I/O processing; it now performs batched
          character transfers, an improvement over  the  character-at-
          a-time behavior (a bug) exhibited by System III.

               The KMC-11B, as well as the KMS11  (KMC11  plus  DMS11-
          DA),  is  also  used  as  the  ``Programmable Communications
          Device'' (PCD) on which link-level protocols are implemented
          under VPM.

          2.4.4  VPM  The Virtual Protocol Machine (VPM) is a  package
          which  supports a high-level definition language for level 2
          protocols to be handled by an interpreter running in a  PCD.
          In  this  manner,  IBM  RJE,  a  synchronous pseudo-terminal
          interface, and several network protocols, including X.25 but
          not TCP/IP, may be supported.

          2.4.5  Synchronous terminal  System V documents support  for
          a  synchronous  terminal  interface  utilizing  the  Virtual
          Protocol  Machine,  but  it  was   not   included   in   the

          2.4.6  BLIT  At the time of this writing, the driver for the
          Teletype  5620  bit-mapped  terminal was available only as a
          System V-compatible binary object.

          2.4.7  Ptys  4.1C has a pseudo-terminal  driver  to  support
          network  connections.   This  is  actually  a driver for two
          devices, a slave (/dev/ttyp?) and a master (/dev/ptyp?) end,
          where  the slave end looks exactly like an ordinary terminal
          and the master end (used by network daemons such as  rlogind
          and  telnetd)  has a few extra ioctls to aid in simulating a

               This device is quite important in the common  situation
          in which there are few directly-connected terminals and most
          users log in over a local network.

               Pseudo-terminals are also important for  such  programs
          as Emacs and script.

          2.4.8  Generalized disk driver     System V    provides    a
          generalized  driver  gd for several moving-head disks (RM05,
          RM80, RP04/5/6/7).

               The System V driver may be derived from the Berkeley hp
          driver, which supports all MASSBUS drives.

                                     - 16 -

               The  drive  type  is  determined  in  both  systems  by
          examining  the device type register and then using different
          parameter tables per drive.

          2.4.9  Generalized tape driver  A generalized tape driver gt
          similar  to  the  generalized  disk  driver  is  provided by
          System V.  This driver offers a  general  interface  to  the
          TE16 and TU78 style tape drives.

               The Berkeley ht drivers support all MASSBUS tape drives
          except the TU78, which is supported by the mt driver.

               Again, device information is  determined  by  examining
          the device hardware type register.

          2.5  File Formats

               A few file formats are worth mention.   In  particular,
          System V has reorganized several standard file formats, with
          important consequences.

          2.5.1  A.out  The details of the binary object  file  format
          for  commands  are  sufficiently  different  between the two
          systems that it is not possible to run an object  file  from
          one system on the other.

               The Common Object File Format (COFF) has  been  adopted
          in  System V as the standard output format for programs such
          as as and ld in  an  effort  to  provide  uniformity  across
          several  processors  and  compatibility  with  certain other
          operating systems.  The traditional  UNIX  a.out  header  is
          included  as  a  part of the COFF header information.  Other
          COFF information includes such things as the architecture of
          the  host  on  which the file was created, line numbers if a
          symbolic debugging option was in effect at compile time, and
          so forth.

               The convert utility may be used to convert pre-System V
          objects to COFF.

          2.5.2  Ar  The System V format for file archives has changed
          somewhat  from previous releases of UNIX.  In particular, an
          archive now includes a symbol  directory  created  from  the
          symbol  tables  of  all archive members which are in COFF to
          allow ld to  perform  random  access  on  the  archive.   In
          addition,   numeric   data   in   headers  (archive,  symbol
          directory, member) is stored as 4-byte quantities and should
          be portably accessed using the sputl and sgetl library calls
          from libld.a.

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                                     - 17 -

               The  portable  ar  command  creates   archive   headers
          specific  to  the  host.  Arcv is still available to convert
          old-style  archives  from  PDP-11  to   VAX-11/780   format.
          However,  convert  should  be  used  to convert pre-System V
          archives to the newer format.

               4.1C has the ranlib program for inserting an  index  at
          the  beginning  of  an  archive,  so that the archive can be
          randomly accessed.

               The Berkeley ar (introduced in 4.1BSD)  produces  ASCII
          output, making the archives portable without the need of any
          special libraries.

          2.5.3  Fs  We consider this topic sufficiently important  to
          have a major section to itself later in the paper.

          2.5.4  Termcap and descendants  4.1C  includes  the  termcap
          facility,  which  maps  common terminal control functions to
          the specific escape sequences for a particular terminal, and
          the  curses library of cursor motion optimization functions.
          These are used by a number of  programs,  including  the  vi
          editor,  to  achieve  terminal  independence.   System V has
          adopted termcap but not curses.

               Termcap  has  spawned  various  lookalikes   in   4.1C.
          Printcap  is used by lpr to determine the characteristics of
          printers (see above under Printing).   Disktab  is  used  by
          newfs to determine how to configure a new format file system
          (see below under File Systems).  Remote is used by tip  (the
          successor  to  cu)  to  determine  the  characteristics of a
          remote system (see below under UUCP).

          2.6  Games

               Both systems provide a variety of games,  ranging  from
          the  ever-popular  hunt-the-wumpus  to  chess  and automated
          Dungeons and Dragons.

          2.6.1  System V games  On System III, most of the games were
          shell scripts which echoed the message:

                       this game does not work on the VAX

          This deplorable situation  has  been  largely  corrected  in
          System V.

          2.6.2  4.1C BSD ASCII graphics games   4.1C   has   numerous
          games which use termcap and curses to produce ASCII graphics
          on various terminals. Examples  are  rogue  (a  role-playing
          game  in  the  manner of Dungeons and Dragons), worms, rain,

                                     - 18 -

          canfield, and mille.

               System V has the snake game, but for  some  reason  has
          removed  the  termcap  support, making it work on only a few
          terminal types.

          2.6.3  PDP-11 compatibility  4.1C provides a  package  which
          allows  the  use  of the PDP-11 compatibility feature of the
          VAX  processor.  This  package   was   supposedly   included
          originally  to support the PDP-11 binary of the game dungeon
          (zork).  The fact that it  is  still  included  under  games
          seems fitting.

          2.7  Miscellany

          2.7.1  File system hierarchy  The most notable addition here
          is /usr/ucb, which 4BSD uses to contain objects for commands
          developed at Berkeley (though not all  such  commands),  and
          /usr/local,  used  to  contain  commands  and  libraries (in
          /usr/local/lib)  that  exist  at  Berkeley   but   are   not
          distributed  (making  this  a  convenient place for commands
          developed at other sites).

               See below under Sources and Documentation for  comments
          on the source trees.

          2.8  Maintenance

               4BSD  has  a  reputation  in  some  quarters  as  being
          unsuitable  for  production  use  because  it  is a research
          system.  This reputation is undeserved, as  its  maintenance
          facilities are more highly developed than those of System V.

          2.8.1  Init, getty, and login   Init  and  getty   are   not
          substantially  different  in  4.1C from 4.1.  Login has been
          modified  to  handle  rlogin-style  remote  logins   without
          passwords  on machines under the same administration.  There
          are also the modifications  from  4.1  related  to  shutdown
          (disallowing   logins   before   a  shutdown)  and  security
          (prohibiting login by superuser on certain  terminals,  such
          as dialups).

               On the other hand, the finite  state  machine  approach
          used  for  System III  init  has  been greatly elaborated in
          System V.

               Init is  driven  from  the  file  /etc/inittab,  as  in
          System III.   This  file  is  used  to specify the identity,
          behavior, and arbitrary id of the processes to be associated
          with  each  state  init  can  occupy.  A typical entry might
          specify that in a state commonly corresponding to multi-user

                                     - 19 -

          mode, a getty should be respawned on each terminal line when
          the death of a previous getty is detected. Single-user  mode
          is  a  distinguished  state,  with  the  option  of having a
          virtual system console connected  to  any  terminal.   State
          change instructions are issued to the ancestral init via the
          telinit command.

               The System V getty is  likewise  driven  from  a  file,
          /etc/gettydefs.  This file includes, for each speed, initial
          and final flags used for setting  the  mode  of  a  terminal
          line,  the  login  herald,  and  the  next  speed to try. In
          actuality, the  speed  is  only  a  label  for  which  getty
          searches,  so  that it is possible to make terminal-specific
          entries  which  include  control  sequences  in  the   login
          message, etc.

               System V login has mainly been changed to deal with the
          new  utmp  structure. In addition, environment variables may
          be set in the login response.

               In passing, we note that the old UNIX standby, who, has
          been turned into a general utility for summarizing /etc/utmp
          and /etc/wtmp. To this end, it now has  no  fewer  than  ten
          different options.

          2.8.2  Shutdown, halt, and reboot  4.1C has  the  convenient
          commands shutdown (bring the system down politely, informing
          the users), halt (stop the system immediately),  and  reboot
          (shutdown and bring up a new system).

               When coming up, 4.1C automatically performs fsck on all
          the  file systems (running one fsck subprocess per disk arm,
          in parallel, for speed) and brings the system up  in  multi-
          user  mode.   To bring 4.1C up from a dead start, it is only
          necessary to turn the power switch on.  (To get into  single
          user mode, one types ^C or uses another available method.)

               The normal method for bringing down System V is to  run
          the  shell  procedure  shutdown.  Other facilities exist for
          terminating running processes, including killall, invoked by
          shutdown,  and fuser, which selectively identifies and kills
          processes which are using specified files.  A reboot command
          is  documented  for  the  WECo 3B20S release of System V but
          none seems to  be  available  for  the  VAX.   System V  has
          nothing equivalent to the 4.1C BSD halt command.

          2.8.3  Backups  4.1C uses dump for file system  backups,  in
          the  V7  manner.   The  user  interface  to  restor has been
          modified, however, to resemble that of tar, making  it  much
          easier  to  use, as it is now possible to restor by file (or
          even directory) name, rather than by inode number.

                                     - 20 -

               The 4.1C dump also allows backups  over  networks.   It
          runs  at  tape  speed, and is fast enough (especially with a
          6250bpi  tape  drive)   that   disk-to-disk   backups   seem

               Several backup paths are available under System V.  The
          volcopy  utility  from  System III  may  be  used  to copy a
          complete file system. The new finc offers a fast incremental
          backup  of  those  files  meeting certain selection criteria
          (last access, modification,  etc.).  Frec  may  be  used  to
          recover  files  by  inumber  from  a volcopy or finc backup.
          Finally, ff,  a  fast  version  of  find,  may  be  used  in
          combination  with  cpio.  Dump and restor are not present in
          System V.

          2.8.4  Fsck, fsdb, etc.   A  slightly  improved  version  of
          fsdb, the interactive file system debugger under System III,
          is offered in System V.

               Fsck, the file system checker, has  been  augmented  by
          dfsck,  invoked  by checkall, which allows simultaneous file
          system checks on two  different  drives.   Note  that  dfsck
          relies  on  the  system  being  configured to use System V's
          multiple physical I/O buffer facility.   Also,  the  use  of
          dcopy  to  reorganize the file system for faster access (see
          below under File System) will contribute to faster checking.

               4.1 added the -p option to fsck, which applies  default
          rules  to  preen  file  systems  (usually  on  reboot),  and
          incidentally allows concurrent checking of file  systems  on
          different disk arms to speed rebooting.  This is retained in

               4.1C and 4.2, unlike 4.1, but like System V, requires a
          reboot after fsck modifies the root filesystem.  In 4.1C and
          4.2, unlike System V, the reboot is handled automatically.

          2.8.5  Monitoring and debugging  System V  provides  various
          facilities  inherited  from System III for monitoring system
          activity and dealing with problems.

               An operating  system  profiling  package  is  available
          which   uses   the  pseudo-device  /dev/prf  to  access  the
          operating  system  and  collect  performance  statistics  by
          monitoring selected text addresses.

               Extensive error logging and reporting is performed by a
          daemon which accesses the /dev/error interface to the system
          error collection routines. These reports are often  valuable
          in analyzing suspected hardware difficulties.

                                     - 21 -

               The  crash  program   provides   a   reasonably   clean
          interactive   utility  for  debugging  core  images  of  the
          operating system after a crash.  It  may  also  be  used  to
          browse through a running system.

               4.1C has syslog to collect kernel error  messages  into
          /usr/adm/messages.  Arrangements have also been made to send
          many error messages directly to the controlling terminal  of
          the process that caused them.

               There are provisions for analyzing  the  state  of  the
          paging  system after a crash with analyze.  There is a paper
          on debugging the kernel with  adb  that  tells  how  to  use
          numerous  canned  shell  scripts  to examine various tables.
          Adb itself has the -k option for  setting  its  memory  maps
          appropriately for the kernel.

          2.8.6  Accounting   System V  provides  accounting  software
          appropriate  for  a production system in the form of several
          tools used to create complex combined reports.  The graphics
          facilities  may  be  used  to  automatically  produce charts
          showing various system parameters (disk reads and writes per
          head,  number of swaps in and out, kernel buffer statistics,
          etc.).  These have useful impact in justifying your facility
          to upper-level management.

               4.1C has kernel hooks  to  collect  similar  accounting
          information  (including  paging  statistics)  but  lacks the
          graphical output facilities.  The facilities provided proved
          quite  adequate for the purposes of actual system management
          in a non-billing environment, however.

          3.  Installation and Configuration

               The  installation  and  configuration   documents   are
          sufficiently   complete   that   few   problems   should  be
          encountered  when  following  their   instructions.    Known
          problems are noted below.

          3.1  Installation

               Both systems are  delivered  in  the  traditional  Unix
          format,  viz.  a  set of half inch magnetic tapes containing
          copies of all the binaries, source code, and  documentation,
          plus  accompanying  hardcopy documentation (Western Electric
          sells  manuals  ready  for  use,  while  Berkeley   supplies
          duplication-quality  masters).  4.2 will come with a console
          cassette and floppy, so it will no longer  be  necessary  to
          hand-code initial bootstraps.

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                                     - 22 -

               System V  binary  licenses  are  available,   and   the
          Berkeley  distribution  is  also  available on two RK07 disk

               For  those  unfamiliar  with  VAXen,   Installing   and
          Operating   4.1C BSD   contains  sections  on  VAX  hardware
          terminology and disk formatting which have  no  counterparts
          in  Setting  Up  the  UNIX System (the System V installation

               Both systems provide  a  disk  formatter.   The  format
          command  provided with System V will format RP06 and RM03/05
          disks.  The formatter of 4.1C and  4.2  formats  almost  any
          non-DEC UNIBUS or MASSBUS drive, and also includes RM03s and
          RM05s, i.e., any disk with the BSC bit in  the  header.   It
          cannot  handle  RP06, RP07, or UDA50s, but the DEC formatter
          can do those.

               We had no real problems booting  either  system.   (The
          System III boot bugs seem to be fixed in System V.)

          3.2  Configuration

               Both systems are relatively easy to configure.

               System V includes driver support for  most  devices  of
          interest, including the RM05, RM80, and RP04/5/6/7 disks.

               4.1C BSD supports all of the  devices  just  mentioned,
          plus   many   others,   and   also   understands   the  full
          interconnection architecture of  the  VAX,  so  that  it  is
          possible to have, say, two RP06's on one MASSBUS and another
          on a second, and the system may be permitted  to  decide  at
          configuration time which MASSBUS's the RP06's are on.

               System V is configured by running  the  config  program
          against  a  system description file; entries in the file are
          checked against a list of supported devices in  /etc/master.
          The  vcf  command  may  then  be  used in standalone mode to
          verify address  and  interrupt  information  in  the  kernel
          object against the actual hardware present on the system.

               4.1C and 4.2 are configured with a config program  too,
          but  this  one  works markedly differently.  The sources are
          arranged in such a way that several different  kernels  (for
          the  same or different machines) can easily be made from the
          same  sources.   Things  such  as  network  node  names  are
          parameterized at run time so that the same kernel can easily
          run on several machines with the same CPU  and  peripherals.
          If  desired,  a  generic kernel (such as on the distribution
          tape) can be configured that will  find  likely  devices  at

                                     - 23 -


               System V  still  requires  hand-setting   of   numerous
          parameters,  such  as the number of process, file, and inode
          table slots, while 4BSD (4.1 and later) decides  appropriate
          values for these parameters on the basis of one number:  the
          number of users the machine is  to  support.   (The  default
          rules can be overridden, of course.)

          3.3  Transition

               The transition from 4.1BSD to 4.1C BSD (or 4.2)  should
          not   be   very   troublesome.    Though   the  file  system
          implementation is quite different,  the  user  interface  is
          almost  identical,  especially  since system calls that have
          been replaced are simulated.  The long file  names  are,  of
          course,  not  a  problem.   The  new  directory format might
          appear to be, but there should be few  programs  other  than
          system  ones  (which  are  supplied)  that  read directories

               Directions   for   the   transition   are   given    in
          Installing/Operating  4.2bsd under the section ``Upgrading a
          4BSD System,'' and A 4.1a  User's  Guide  to  4.1c  provides
          useful user orientation.

               There are no provisions for  upgrading  from  a  system
          previous  to  4BSD,  such  as  3.0 or 32V, though this could
          presumably be done with sufficient investment of effort.

               System V is distributed  with  a  document,  Transition
          Aids,   designed  to  assist  the  system  administrator  in
          changing from System III to System V.

               Especially crucial transition topics include:  hardware
          support  changes  (esp.  lack  of DH-11 support); whether to
          convert to a 1K file system; conversion to the  new  archive
          format;   and   conversion   of   objects   or  (preferably)
          recompilation of sources for user programs to accomodate the
          new headers and object file format.

          4.  Sources and Documentation

               There has been a  large  amount  of  reorganization  of
          sources, documentation, and associated support since 32V.

                                     - 24 -

          4.1  Make

               System V includes the  extended  make,  which  features
          many  additional  default rules to handle common conditions,
          to the point that many  compilations  require  no  makefile.
          Additions  are  also  present which handle archives and SCCS
          files (see below) and make use of environment variables  and
          defaults.   Most system programs may be rebuilt by using the
          collection of :mk command files located in the source tree.

               The 4.1C BSD make seems to be very much in  the  flavor
          of  V.7.   Rebuilding the whole source tree is as easy as in
          System V, however, and is recommended to be done frequently.

          4.2  SCCS

               System V includes the PWB Source  Code  Control  System
          (SCCS),  not  available  in  4.1C BSD.   4.2  is  rumored to
          include RCS, a public-domain rendering of SCCS.

          4.3  Sources

               System V preserves the changes to the names  of  source
          directories  and  files  which  System III  introduced  (the
          kernel ``sys''  subdirectory  becomes  ``os'',  and  ``dev''
          becomes  ``io'').   However,  since  there is an appropriate
          makefile (or :mk command file) for almost everything  it  is
          possible  to  go  to  the appropriate parent directory for a
          software package and let make do the work.

               The 4.1C sources,  both  user  and  kernel,  have  been
          radically  reorganized in order to simplify recompilation of
          the entire system and  to  promote  portability.   There  is
          generally  a  source directory subtree corresponding to each
          directory containing  objects,  e.g.,  /usr/src/usr.bin  for
          /usr/bin,  making sources easy to locate.  Good use has been
          made of symbolic links, in order  to  avoid  duplication  of
          sources,  and  to  allow keeping certain pieces (such as the
          kernel sources) on  whatever  file  system  is  appropriate,
          e.g.,  /usr/include/sys  is  a  symbolic link to /sys/h, and
          /sys is itself a symbolic link to /usr/sys.

               The kernel  sources  have  all  the  VAX-specific  code
          separated  out into different directories and files from the
          portable code.  The user sources have  also  been  similarly
          organized  for  portability.   The C library, in particular,
          has been redone.  One would expect 4.1C to be as portable to
          another 32-bit machine as 32V or System V.

               There is a rather widespread problem in  Berkeley  code
          consisting  of  the  use  of the type int when long, or even

                                     - 25 -

          off_t, or especially time_t is meant.  This works  fine,  as
          long  as  you  never try to run such code on a machine where
          int is smaller than 32 bits.  (This problem is  not  evident
          in  the  kernel,  but rather, in application programs.) This
          problem is perhaps less prevalent in 4.1C than in 4.1.

               Fairness  requires  mentioning  that  there  are   also
          numerous  places  in  the documentation where it is asserted
          that int is 32 bits,  on  the  grounds  that  machines  with
          smaller  word  sizes  are  not  sufficient  for  many of the
          functions 4BSD supports.

          4.4  Documentation

               Berkeley provides  the  traditional  Unix  Programmer's
          Manual,  volumes  I, IIA, and IIB, plus an additional volume
          of papers written at Berkeley and related  directly  to  the
          Berkeley  parts  of  the  system.   The  documents  come  as
          duplication quality  masters  of  8-1/2  by  11  inch  pages
          suitable  for  ordinary  three-ring  looseleaf binders.  The
          first volume has of course been updated  and  is  also  kept
          on-line for easy access.

               System V   has   largely   reorganized    the    system
          documentation.  Volume  one  has  been divided into a User's
          Manual, an Administrator's Manual,  and,  peripherally,  the
          Operating  System Error Message Manual.  Most of the classic
          UNIX papers which appear  in  volume  two  in  the  Berkeley
          distribution  have  been pieced together to form such things
          as a Document Processing Guide and a Programming Guide.  All
          in  all,  there  are  twelve  documents  furnished  with the
          purchase of a System V license; extra copies are for sale by
          Western Electric Software Sales and Marketing.

               It is  disappointing  to  note  that  not  all  of  the
          documentation  is  provided  on  the  distribution  tape,  a
          feature  considered  critical  by  some  (e.g.   the  sight-

          5.  Groups and Identifiers

               4.1C changes the implementation of groups  and  related
          identifiers sufficiently to motivate this section.

          5.1  Groups

               System V uses the old V7/32V group scheme: a  user  may
          have  access to a login group (specified in /etc/passwd) and
          also to several other groups (as permitted  by  /etc/group),
          but may be in only one group at a time.

                                     - 26 -

               In 4.1C, the same files in the same  formats  determine
          what   groups  a  user  is  allowed  in,  but  the  user  is
          immediately put in all of them at login: there is no  newgrp
          command.   The  groups  command lists the groups you are in.
          The maximum  number  of  simultaneous  groups  is  a  system
          compile-time  parameter,  and  the  default  is  eight.  The
          setgroups system call can be used (by superuser) to set  the
          groups for a process.

               In  both  systems,  each  file  has  a   single   group
          associated  with it to determine group read, write, execute,
          and setgid permissions.  System V creates a new file in  the
          effective  group  of  the  process, whereas 4.1C creates the
          file in the group of its parent directory.

               Both systems have chgrp (both command and system  call)
          to  change  the  group of an existing file.  4.1C allows the
          user to change the group of a file he owns to be any of  the
          groups  to  which  he  belongs.  System V allows the user to
          change the user and group id  of  any  file  he  owns,  thus
          giving  the file away.  4BSD does not, apparently because of
          the existence of disk space quotas, which System V lacks.

          5.2  Identifiers

               Berkeley has extended  the  setuid  and  setgid  system
          calls in 4.1C to allow setting the effective id to the value
          of the real id, as well as the reverse.  This is very useful
          for things like network server daemons, which may now switch
          permissions between superuser privileges  and  those  of  an
          ordinary  user,  and back, in a single process.  This (along
          with the  socket  IPC  and  non-blocking  I/O)  allows  many
          daemons  to be implemented as one process where formerly two
          were required.

               Group ids and process ids are 32 bit integer quantities
          in  4.1C.   The high order 16 bits of the process id are not
          yet used, but probably  will  be  with  the  development  of
          distributed applications.

          6.  File Systems

               Both systems have file  systems  different  from  their
          predecessors  and  each  other.  Though the comments in this
          section may make the  differences  seem  extreme,  the  user
          interface  is  not much changed in either case from 32V, and
          we have had no trouble transferring files  between  the  two
          systems  with  either  tar  or  cpio  (though cpio had to be
          ported to 4.1C first, of course).

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                                     - 27 -

          6.1  System V

          6.1.1  New file system block size  System V has introduced a
          revised  file  system  which  allows a choice of a 512 or 1K
          byte block. The information concerning the type  of  a  file
          system  is  recorded in its superblock, so it is possible to
          have both kinds of file system on the same system.

               Robustness is enhanced  by  carefully  controlling  the
          order  in  which  inode and directory information is written
          out in order to prevent serious file system  inconsistencies
          in the event of a crash.

          6.1.2  Faster access  Other enhancements claimed to  improve
          efficiency include multiple (3-7) physical I/O buffers (upon
          which dfsck, a multi-drive  version  of  fsck,  depends);  a
          larger  number  of  system  buffers  (up  to 400); free list
          management of the file table; and  hashing  of  the  in-core
          inode table.

               A utility, dcopy, is provided to allow reordering of  a
          file system to optimize access time by compressing directory
          ``holes'' and spacing file blocks  at  the  disk  rotational
          gap. Its frequent use is recommended.

          6.2  4.1C BSD

          6.2.1  Reimplementation for efficiency   4.1C  has  a   file
          system  that  uses a block size and a fragment size that are
          settable per file system.  The  basic  block  size  (usually
          4096  or  8192  bytes)  is  the largest block size used in a
          file, and all blocks but the last are this size.   The  last
          one may be any multiple of the fragment size (usually 512 or
          1024, and no more than a factor of eight less than the basic
          block  size).   Inodes  are  divided  among several cylinder
          groups on a file system, and blocks in a  file  are  usually
          localized  in a single cylinder group.  In-core inode copies
          are hashed.

               The standard I/O library has been modified to  use  the
          block  size  returned by the modified stat call to determine
          the size of its transfers.

               Various changes were  made  for  robustness,  as  well,
          beyond  those found in 4.1.  For example, static information
          from the superblock (such as the block and  fragment  sizes)
          is duplicated in each cylinder group.

               Measurements made at Berkeley  indicate  the  new  file
          system is up to a factor of 16 faster than the old (4.1) one
          under ideal conditions, and a factor of 10 is not unusual in

                                     - 28 -

          actual use.

               4.1C keeps defaults for the various  parameters  needed
          by  the  new  file  system  in  /etc/disktab (a termcap-like
          file), where  newfs  (a  frontend  to  mkfs)  uses  them  in
          constructing a file system, storing them in the super block.
          Various other programs, such as bad144,  which  handles  bad
          sector  marking,  also  use  /etc/disktab.   This  file is a
          kludge used because the information is not yet kept  on  the
          disk and accessible by an ioctl.

          6.2.2  Other modifications  In addition, 4.1C has very  long
          file  names  (compile  time  parameter  of  255  characters)
          analogous to the long C identifiers,  a  reworked  directory
          implementation, symbolic links, and mkdir, rmdir, and rename
          as system calls.

               The use of file names that are actually 255  characters
          long is not, of course, recommended.  The idea is to set the
          limit high enough that ordinary use will never hit it.

               A simulation library for the new directory  format  has
          been  distributed  several  times  over USENET; it is a good
          idea to use it even if conversion to 4.2 is  never  planned,
          since  it  solves several old Unix directory access problems
          (e.g.  insuring null termination  of  file  names  extracted
          from a directory).

               A symbolic link is simply a file containing a pathname,
          which is interpreted by the kernel after the pathname of the
          link  itself.   Thus  cross-device  links   and   links   to
          directories are possible.

               The motivation for moving mkdir, rmdir, and rename into
          the  kernel  was  to  make  them  extensible  in  a  network
          environment.  In  the  case  of  rename,  robustness  during
          system crashes was also a factor.

          6.2.3  Extended (network) file system  Neither 4.1C nor  4.2
          have  the  extended  file  system  that makes it possible to
          mount, on one machine, a file  system  existing  on  a  disk
          connected  to  another  machine,  with  file  transfers then
          proceeding over the network  connecting  the  two  machines.
          There  are  several  implementations  of such a facility but
          none will appear in 4.2.

                                     - 29 -

          7.  Interprocess Communications (IPC)

               This is one of the areas where the systems diverge  the

          7.1  System V

               System V provides several somewhat different paths  for
          achieving  interprocess  communication, mostly developed for
          real time support.

               The  fifo,  or  named  pipe,  has  been  retained  from
          System III, allowing a process to open a pipe by name rather
          than  needing  a  parent  to   set   up   appropriate   file

               The  message  queue  operations  associate   a   unique
          identifier  with  a  system message queue and data structure
          that includes information about the last processes  to  send
          and  receive  messages,  the  times  at  which  these events
          occurred, etc.

               The semaphore operations associate a unique  identifier
          with  a set of semaphores and a data structure that includes
          time  and  pid  of  last  operation,  number  of   processes
          suspended  while  waiting  for  a  particular  change in the
          semaphore's value, etc.

               The  shared  memory  operations  associate   a   unique
          identifier  with  a  shared  memory  segment  (which  may be
          attached to the data  segment  of  a  process)  and  a  data
          structure  containing the size of the segment, time and pid,

               As an adjunct to the  above,  process  segment  locking
          (text,  data,  or  both)  via  the plock system call is also

               The number of  message  queues,  size  of  each  queue,
          number of semaphores, number of shared memory segments, etc.
          are all  parameters  which  are  determined  by  the  system
          administrator at system configuration time.

          7.2  4.1C BSD

               4.1C has dropped the V7 multiplexed files  (MPXs)  that
          were  retained  in  4.1  in  favor  of  a  new  interprocess
          communication facility.  This new socket IPC integrates  the
          pipes,  file  and  device  I/O,  and  network  I/O  into one
          interface,  which  allows  blocking  or  non-blocking   I/O,
          multiplexing  several  I/O  streams in one process by use of

                                     - 30 -

          non-blocking  I/O  and   the   select   system   call,   and
          scatter/gather I/O.

               The socket IPC solves most of the traditional Unix  IPC
          problems,  and  is  more general than the various mechanisms
          which have preceded it, such as pipes, MPXs, Rand ports, BBN
          await/capac, etc.

               The mmap shared memory facility described in the 4.2BSD
          System  Manual  is not supported in 4.1C, and will not be in
          4.2.  It will, however, appear in  4.3BSD,  along  with  the
          revised  fork  system call that makes vfork obsolete by only
          copying pages when they are modified.  Various other  memory
          management-related changes will also come with 4.3.

          8.  Networks

               With  the  increased   use   of   networks   of   small
          workstations  and  larger  file  or  compute  servers,  this
          subject is gaining importance.

          8.1  System V

               While it is said that System VI  will  incorporate  the
          Berkeley  network  code, most network support in System V is
          implemented using KMC-11Bs.

          8.1.1  X.25  System V documents the use of its VPM  facility
          to  support  X.25 in a KMC-11B peripheral processor, and the
          same technique can be used for other networks.  However, the
          X.25  support  package  was not included on our distribution
          tape, and the documentation leads one to  believe  this  was

               Rumor has  it  that  there  is  a  current  project  to
          implement X.25 under the 4.2 network framework.

          8.1.2  PCL network  System V provides a driver for the  PCL-
          11B network bus, used to interconnect multiple CPUs for fast
          parallel communications.  A local network of  UNIX  machines
          is made practical by the inclusion of the net command, which
          allows commands to be executed on remote system.  It is very
          reminiscent of berknet.

               4.2 has a PCL driver.

          8.1.3  NSC network    System V   documents   an    interface
          specification for the NSC A-410 processor and its associated
          software, used to access an NSC  local  net  (Hyperchannel).
          Neither a driver nor applications software was provided with

                                     - 31 -

          the distribution, however.

               4.1C and 4.2 have an NSC driver.

          8.1.4  RJE to IBM   System V   implements   software   which
          communicates   with  IBM  JES  by  emulating  a  360  remote
          workstation. It relies on a VPM script  running  in  a  PCD,
          say,  the  KMC-11B.   Facilities  are  provided for queueing
          jobs, monitoring the status of the RJE, and notifying  users
          of the arrival of output.

          8.2  4.1C BSD

               Networking is one of the strongest points of 4.1C.

          8.2.1  General networking framework  The network  mechanisms
          were  designed with the intention of supporting a variety of
          network protocols and hardware.

               The socket IPC provides an  interface  common  to  both
          networks  (the  internet  domain in particular) and internal
          Unix facilities (the Unix domain).

               The  internal  networking   mechanisms   support   easy
          implementation  of  further  protocols or interface drivers,
          and are clearly documented.

          8.2.2  Variety of hardware and protocols supported  Hardware
          currently supported  includes  several  kinds  of  ethernet*
          interfaces (3COM, Interlan, Xerox 3Mb experimental), several
          ARPANET IMP interfaces (ACC LH/DH, DEC IMP11-A, SRI) a  ring
          network  interface  (Proteon 10Mb), and various others, such
          as DMC-11, NSC Hyperchannel, and Ungerman-Bass with DR-11/W.
          4.2 (but not 4.1C) has a PCL driver.

               ISO/OSI** Network, Transport, and lower layer protocols
          supported include 3Mb and 10Mb ethernet, Proteon proNET 10Mb
          ring, and the DoD internet family (TCP/IP and relatives).


            * Ethernet is a trademark of Xerox Corporation.

           ** International Standards Organization Open Systems
              Interconnection: a meta-protocol designed to promote
              compatibility among networks.

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                                     - 32 -

          8.2.3  Internet (TCP/IP)  Both TCP and UDP are available for
          use  with  IP  either  on  the  local  network  or  over the
          internet.  ICMP is supported, and  there  are  some  gateway

               The  socket  IPC,  together  with  a  network  library,
          provides  many  of  the functions of the Session layer.  The
          socket type SOCK_STREAM, which provides a reliable, ordered,
          byte   stream,   is   currently   supported  by  TCP,  while
          SOCK_DGRAM, providing datagram service, is supported by UDP.
          There is no internet protocol to support SOCK_SEQPACKET, for
          sequenced packets.  SOCK_RAW allows direct  access  to,  for
          instance,  the  IMP interface, for debugging and development
          of new protocols.  Only the superuser is  permitted  to  use
          this socket type.

               At  the  Applications  layer,  the  Internet  protocols
          Telnet, FTP, SMTP, and TFTP are supported.

          8.2.4  Berkeley protocols  The berknet facilities of 4.1 are
          officially removed from 4.1C and 4.2.

               There are  also  various  new  protocols  developed  at
          Berkeley,  including  remote  login among machines under the
          same  administration  without  passwords   (rlogin/rlogind).
          Remote  shells  and  remote  procedure  calls (courierd) are
          supported, as are file copy (rcp/rshd), and status protocols
          such  as  the  one  that  supports rwho and ruptime (rwhod).
          This latter takes advantage of the broadcast packet facility
          of  Ethernets and rings to exchange status information about
          who is on what system and what systems are up on  the  local
          network.  (The idea is easily extensible to networks without
          broadcast packets.) Some of these protocols use UDP and some
          use TCP.

               These protocols make use of  several  machines  over  a
          local network or networks quite convenient.

          8.3  UUCP

               Both systems support UUCP, though the details  diverge:
          System V  allows uucp copy addresses to specify paths across
          multiple systems (as for mail),  while  4.1C  still  permits
          copies   only  between  adjacent  systems.   Naturally,  all
          systems in a multisystem path  must  be  running  uucp  with
          forwarding to properly effect forwarding.

               4.2 has  all  well-known  uucp  bugs  fixed.   It  also
          supports  more than half a dozen auto-dialers.  The spooling
          directories have been made sane.

                                     - 33 -

               The cu command is retained in System V, but dropped  by
          4.1C  in  favor  of  tip.   Tip gets parameters for a remote
          system from /etc/remote (yet another termcap-like  file)  so
          it is possible to just type

               tip system-name

          and be connected to the remote system (whose  name,  system-
          name,  is  in /etc/remote), without having to know the phone
          number or devices involved.

               If the cu interface is desired, linking tip  to  cu  is
          all  that  is  required to get it.  Various cu-like commands
          are supported directly by tip.

               System V includes a  library  routine,  dial,  used  to
          establish  a dialout connection. This routine is used by cu,
          but, curiously, uucico still relies on the same  old  conn.c

          8.4  USENET

               Neither system includes USENET  news  program  sources.
          4.2  will  provide both USENET programs (readnews, postnews,
          et al.) and notesfiles, as user contributed software.

               In any case, the best version of news is clearly  Bnews
          2.10, which has been distributed over USENET.  One method to
          get it might be to set up a UUCP connection to a neighboring
          USENET site and copy it over.

               The USENET and UUCP  networks  have  become  widespread
          enough that connection to them is certainly beneficial.

          9.  Performance

               This is a sticky issue  which  we  will  not  treat  in
          detail,   as   this   is   not   a   performance  evaluation
          presentation.  We will give a few tentative benchmarks,  and
          mention two qualitative performance areas.

          9.1  Some Qualitative Remarks

               Two important areas where performance varies widely due
          to  system  configuration  and usage are paging vs. swapping
          and terminal I/O.

          9.1.1  Paging vs. swapping  System V, like System III,  32V,
          V7,  and all the PDP-11 Unixes, swaps, while 4.1C, like 4.1,
          pages.  With enough memory on a VAX-11/780, it is  difficult

                                     - 34 -

          to  tell  the  difference  for  a  load  of small processes,
          because System V just doesn't swap.

               If it is desirable to run huge  graphics  processes  or
          many  Emacs editors or the like, the telling point is not so
          much the performance as the virtual address  space  provided
          by  the 4.1C paging system.  Such things as LISP require the
          large address space paging provides, and Ingres is much more
          usable  with  it, since it can run as one process instead of
          half a dozen.

               We certainly do not intend to indicate,  however,  that
          we think paging and swapping produce equivalent performance.
          There are many technical papers on  comparative  performance
          that  indicate  paging  gives much better performance; it is
          merely that our (admittedly  idiosyncratic)  experience  was
          that  under  a  light load it is hard to tell the difference
          without measuring it.

          9.1.2  Terminal I/O  Using DH11 terminal  controllers,  4.1C
          provides  reasonable terminal I/O performance.  Berkeley has
          modified  the  DZ11  driver  sufficiently  that  even  these
          (basically  interrupt per character) devices are usable.  It
          should  be  remembered  that  DEC  does  not  provide   DH11
          controllers for VAXen.  This affects DEC maintenance, though
          similar hardware is available from other vendors.

               If you need numerous terminals running at 9600 baud  or
          higher, the System V combination of DZ11s and KMC11 terminal
          controllers seems preferable.  The other side of  this  coin
          is  that  little  choice  has  been left for System V users,
          since  DH-11  driver  support  is  not   included   in   the
          distribution  and  since  DZs  alone  are  unlikely to yield
          acceptable response.

          9.2  Tentative Benchmarks

               These measurements were taken on a VAX-11/780 with  six
          megabytes of memory and a single RP07 disk.

               The disk was partitioned into three sections which  had
          similar  sizes under the two operating systems.  The various
          kernel parameters were chosen by  configuring  4.1C  for  32
          users,  and,  for System V, by picking the largest parameter
          values  suggested  in  the  documentation.   The   resulting
          numbers  of  buffers,  inode and file structures, etc., were
          similar.  Memory was interleaved.

               No particular care was taken beyond these steps to tune
          either system to its maximum performance.

                                     - 35 -

               The numbers given here should not taken too  literally,
          but only as indicative.

          9.2.1  Load simulation  This was done using a  program  that
          forks ptys instances of itself, and then each pty* repeats a
          job forever, or rather, until the run is over, as decided by
          the original parent program.   The  job  is  a  brief  shell
          script  that  uses commands common to both systems, as found
          on each system.  Sources to compile with cc were taken  from
          System V  to  avoid  the  long  filename problem.  They were
          carefully picked to avoid any System V  peculiarities,  such
          as  getopt.   Files  to  use with nroff were also taken from
          System V, for no particular reason.

               The output was redirected to a file to  avoid  terminal
          I/O considerations.

               Repeated runs  were  taken  until  the  job  throughput
          stopped  decreasing  due  to  file  system degradation.  The
          following figures were obtained:

               ptys              1     2     4     8    16

                                System V

               jobs/hour/pty   46    25    13    6.4   3.2
               jobs/hour       46    50    51    51     51

                                4.1C BSD

               jobs/hour/pty   60    32    16     8      4
               jobs/hour       60    64    64    64     64

               The total number of jobs per  hour  increased  slightly
          from one to two ptys, and then remained constant, as all CPU
          cycles were absorbed.  The number of jobs  per  pty  is,  of
          course, just the total divided by the number of ptys.

               We  interpret  these  results  to  mean  that  4.1C  is
          noticeably  faster  than  System V.   We  do  not  state the
          obvious figure of 25%, because the results could  easily  be
          varied by, for instance, increasing the amount of file I/O a
          job uses (to take advantage of the faster 4.1C file system),


            * No pty devices were used:  this term is used only for

                                     - 36 -

          or by using larger processes (to  force  System V  to  swap,
          which it never did with the above job).

               Tuning either kernel could, of course, vary the results
          either way.

               Definitive benchmarks will have to await the release of

          9.2.2  File system throughput  Our experience has been  that
          the  4.1C  filesystem  is  markedly faster than the System V
          one.  However, the actual figures vary so much according  to
          the  size  of  the  files used, the transfer block size, the
          filesystem block size, whether memory is interleaved or not,
          etc.  (though  under  all  conditions  we have tried 4.1C is
          faster than System V), that it would take  some  months  and
          another paper the size of this one to deal with the problem.
          Rather than present partial and possibly misleading figures,
          we have decided to not present any.

          10.  Vendor Support

               The  amount  and  variety  of  support  for  UNIX   has
          increased dramatically over the last few years.

          10.1  Western Electric

               Western Electric supports System V  on  VAXes  and  the
          larger  PDP-11s,  providing  software  assistance  and  user
          training.  (User training is now available, though  software
          assistance has apparently not yet been fully implemented.)

          10.2  U.C. Berkeley

               The  University  of  California  at  Berkeley   cannot,
          because  of the nature of the institution and of the funding
          used to support the development of  Berkeley  UNIX,  provide
          commercial  support.   They do, however, accept bug reports,
          which may affect future versions.  See below on DEC.

          10.3  DEC

               Digital Equipment Corporation has announced  they  will
          support  UNIX in the manner they have supported VMS as a VAX
          operating system (and they will also support it  on  PDP-11s
          (V7M)).   This  is apparently basically Berkeley UNIX, i.e.,
          4BSD (and 2BSD).

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                                     - 37 -

          10.4  Third Parties

               The number of organizations  dealing  with  UNIX  these
          days is quite large.

          10.4.1  OEMs   Many  companies  bringing  out  new  Motorola
          68000-based  systems  recently have chosen System III as the
          base for their operating system, with the apparent intention
          of  moving  to System V.  To some extent, this will no doubt
          lock  them  into  System V,  and  persons  wanting  to   buy
          something close to a small turnkey system will probably wind
          up with essentially Bell UNIX.

               Other   manufacturers   with   microprocessors   likely
          targeted for System V ports are Intel, National, and Zilog.

               There are several ports of 4.1 to  the  68000,  and  at
          least  one of 4.2.  There are also at least two ports of 4.1
          to the National Semiconductor 16032.

               Several of the vendors offering System III based  68000
          systems  claim  to  support  ``Berkeley  enhancements,'' the
          interpretation of which varies between vendors, but  usually
          seems  to include vi, ex, termcap, and curses, and sometimes

          10.4.2  Emulations  Several emulations of UNIX are available
          from third parties, either software vendors or universities.
          Typically these are designed to provide a  UNIX  environment
          on  top  of  another  operating  system,  generally VMS. The
          quality  of  emulation   varies   from   implementation   to
          implementation,  as does the concept of what ``UNIX'' should
          look like.

               On  a  slightly  different  note,  a  package  will  be
          available  from  BRL  in the very near future which emulates
          System V on top of 4.2BSD.

          10.4.3  Consultants  There is a new class of companies  that
          produce  neither  hardware  nor software but instead provide
          assistance in obtaining and supporting both.   These  mostly
          try to cater to the markets for both systems.

               There is a large amount of free software available  for
          4.1 (and thus 4.1C) that was written principally at academic
          institutions.  Much of it is portable  to  System V,  though
          something  like Interlisp that requires a huge address space
          is not, and there are problems with many things  like  Emacs
          because of the use of long identifiers.

                                     - 38 -

               Most commercial vendors attempt  to  produce  and  sell
          software packages to run on either variety of UNIX.  Bell is
          among  these  vendors,  with  the  TITroff  package,  the  S
          statistical package, etc.

               Many  of  the  commercial  vendors   using   System III
          (System V)  have  produced graphical, menu-driven interfaces
          for the naive user, so that it is never  necessary  to  deal
          directly  with any UNIX shell.  These mostly require bit-map
          terminals, varieties of which are also available from  other

               The famous Bell Blit bitmap terminal is available  from
          Teletype  (model 5620).  Unfortunately, as noted previously,
          the Unix software is available only as a System V binary.

          10.4.4  Authors  A number of books designed  to  assist  the
          new UNIX user have recently appeared.

               Most of these either attempt to steer a neutral  course
          by  describing  what  is  essentially  V7,  making them less
          useful in either a 4.2 or System V context, or they  closely
          follow  System III (V) in hopes of describing what will come
          to be a ``standard''.

               The 4.1C (4.2) user is left with the  traditional  task
          of reading the manuals.

          11.  Conclusion

               A brief summary may be useful.

          11.1  Selection Criteria

               One may choose either Berkeley  or  Bell  Unix  on  the
          basis  of  a  particular  needed  function,  such as network
          support, because of performance  in  one  area  or  another,
          because  of  the support of a particular vendor, or for some
          other reason.  We have touched on all these areas above,  we
          hope  in  sufficient  detail to indicate the capabilities of
          the two systems, so that  areas  for  further  investigation
          will be clear.

          11.2  Combinations

               For companies with the resources, the best solution  is
          probably  to  run  either  4.1C BSD or System V and port the
          desired facilities of the other.  This  is  the  traditional
          route. An alternative is the aforementioned package from BRL
          or something similar.

                                     - 39 -

               Even companies with no desire to merge the two  systems
          would  be  well-advised  to  get some sort of expert support
          (whether in-house or not), as neither Bell nor Berkeley  can
          be   counted   on   to   offer   the  really  broad  support
          traditionally  supplied  by  hardware  vendors   for   their
          operating systems.  This situation may change in the case of
          System V  as  more  sites  begin  running  the  system   and
          demanding  the  support  which has been promised, but at the
          moment only time will  tell.   The  same  applies  to  DEC's
          support of 4BSD.

          11.3  Future Directions

               A few recent developments may  indicate  a  trend  away
          from  continued  fragmentation  of  the  UNIX community, and
          especially from the divergence of  the  systems  offered  by
          Berkeley and Bell.

          11.3.1  UNIX standards committee    The   /usr/group    UNIX
          standards   committee  appears  to  be  making  progress  in
          standardizing at least the  most  basic  facilities  of  the
          operating system, and has representatives from most segments
          of the community.

          11.3.2  Berkeley features and Bell  The inclusion of vi, ex,
          and termcap in System V, as well as the adoption of a 1Kbyte
          block file system, shows that Bell  is  aware  of  the  work
          Berkeley  has  been  doing  for  years  in  researching  new
          directions.  Perhaps System VI will go  further  and  adopt,
          for instance, csh, and paging.

          11.3.3  Bell licensing and Berkeley   Unfortunately,   until
          recently  it  has  not been possible for Berkeley to include
          software from Bell licenses  later  than  32V,  because  the
          price  would  have been prohibitive for many of the Berkeley
          licensees.  Though the recent reform of  Western  Electric's
          licensing  scheme apparently came too late to affect 4.2BSD,
          perhaps we will  see  Berkeley  adopt  some  later-day  Bell

          Appendix A:  Terminology

               The official names of the various versions of the  Unix
          System  developed  by  Bell  Laboratories  and previously or
          currently available from Western Electric are:

             o+ UNIX Time-Sharing System, Sixth Edition (V6);

             o+ UNIX Programmer's Work Bench (PWB), V6 plus SCCS, etc.;

                                     - 40 -

             o+ UNIX Time-Sharing System,  Seventh  Edition  (V7),  the
               PDP-11 version of the first portable UNIX system;

             o+ UNIX/32V Time-Sharing System Version  1.0  (32V),  like
               V7, but for the VAX;

             o+ UNIX System III (System III), combining  PWB,  V7,  and

             o+ UNIX System V (System V), now being licensed.

               There   have   been    numerous    Berkeley    Software
          Distributions  of  the various Berkeley versions of the Unix

             o+ 2BSD is used herein as a generic term  for  the  PDP-11

             o+ 2.8BSD is the latest  PDP-11  distribution  in  general

             o+ 2.81BSD was a an intermediate  system  that  was  never
               officially  distributed,  but  is  in  use  at  several
               ARPANET sites with a port of the 4.1A network  software
               incorporated into it.

             o+ 2.9BSD is the distribution just now being licensed, and
               is said to make a PDP-11 look like a VAX 4BSD system.

             o+ 3.0BSD was the first paging system for the VAX, derived
               from 32V.

             o+ 4.0BSD was the second Berkeley VAX distribution.

             o+ 4BSD is used herein as a generic term for any  Berkeley
               VAX distribution from 4.0BSD on.

             o+ 4.1BSD is the VAX distribution in most common use,  and
               contains numerous improvements over 4.0BSD.

             o+ 4.1A BSD, 4.1B BSD, 4.1C BSD were versions intermediate
               between  4.1  and  4.2.   None  of  them were available
               outside of Berkeley except for beta test, and  none  of
               them can be ordered from Berkeley.

             o+ 4.2BSD will presumably be licensed soon.

                                     - 41 -

          Appendix B:  Load Simulation Job

               This is contents of the shell file that was used in the
          load simulation:

               mkdir $1; cd $1

               cc -o simple -p ../simple.c
               nroff -man ../prof.1
               prof simple
               tar -cvf /dev/null ../simple.c simple mon.out
               rm simple mon.out
               nroff -man ../termio.7
               cc -o cmp ../cmp.c

               cd ..
               rm -rf $1

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