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                      Preface to the Second (1995) Edition

   Plan 9 was born in the same lab where Unix began. Old Unix hands will
   recognize the cultural heritage in this manual, where venerable Unix
   commands live on, described in the classic Unix style. Underneath, though,
   lies a new kind of system, organized around communication and naming
   rather than files and processes.

   In Plan 9, distributed computing is a central premise, not an evolutionary
   add-on. The system relies on a uniform protocol to refer to and
   communicate with objects, whether they be data or processes, and whether
   or not they live on the same machine or even similar machines. A single
   paradigm (writing to named places) unifies all kinds of control and
   interprocess signaling.

   Name spaces can be built arbitrarily. In particular all programs available
   to a given user are customarily united in a single logical directory.
   Temporary files and untrusted activities can be confined in isolated
   spaces. When a portable machine connects to the central, archival file
   system, the machine's local name space is joined smoothly to that of the
   archival file system. The architecture affords other unusual abilities,

           Objects in name spaces imported from other machines (even from
           foreign systems such as MS-DOS) are transparently accessible.

           Windows appear in name spaces on a par with files and processes.

           A historical file system allows one to navigate the archival file
           system in time as well as in space; backup files are always at

           A debugger can handle simultaneously active processes on disparate
           kinds of hardware.

   The character set of Plan 9 is Unicode, which covers most of the world's
   major scripts. The system has its own programming languages: a dialect of
   C with simple inheritance, a simplified shell, and a CSP-like concurrent
   language, Alef. An ANSI-POSIX emulator (APE) admits unreconstructed Unix

   Plan 9 is the work of many people. The protocol was begun by Ken Thompson;
   naming was integrated by Rob Pike and networking by Dave Presotto. Phil
   Winterbottom simplified the management of name spaces and re-engineered
   the system. They were joined by Tom Killian, Jim McKie, and Howard Trickey
   in bringing the system up on various machines and making device drivers.
   Thompson made the C compiler; Pike, window systems; Tom Duff, the shell
   and raster graphics; Winterbottom, Alef; Trickey, Duff, and Andrew Hume,
   APE. Bob Flandrena ported a myriad of programs to Plan 9. Other
   contributors include Alan Berenbaum, Lorinda Cherry, Bill Cheswick, Sean
   Dorward, David Gay, Paul Glick, Eric Grosse, John Hobby, Gerard Holzmann,
   Brian Kernighan, Bart Locanthi, Doug McIlroy, Judy Paone, Sean Quinlan,
   Bob Restrick, Dennis Ritchie, Bjarne Stroustrup, and Cliff Young.

   Plan 9 is made available as is, without formal support, but substantial
   comments or contributions may be communicated to the authors.

                                                     Doug McIlroy
                                                     March, 1995

                                                     Copyright (c) 2000
                                                     Lucent Technologies Inc.
                                                     All rights reserved.