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.TL
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Preface to the Second (1995) Edition
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.PP
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Plan 9 was born in the same lab where Unix began.
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Old Unix hands will recognize the cultural heritage in this manual,
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where venerable Unix commands live on,
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described in the classic Unix style. Underneath, though, lies
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a new kind of system, organized around communication and
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naming rather than files and processes.
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.PP
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In Plan 9, distributed computing is a central premise,
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not an evolutionary add-on. The system relies on a
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uniform protocol to refer to and communicate
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with objects, whether they be data or processes, and whether or
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not they live on the same machine or even similar machines.
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A single paradigm (writing to named places) unifies
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all kinds of control and interprocess signaling.
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.PP
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Name spaces can be built arbitrarily. In particular all
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programs available to a given user are customarily united
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in a single logical directory.
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Temporary files and
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untrusted activities can be confined in isolated spaces.
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When a portable machine connects to the
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central, archival file system, the machine's local
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name space is joined smoothly to that of the archival file system.
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The architecture affords other unusual abilities, including:
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.IP
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Objects in name spaces imported from other machines (even from
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foreign systems such as MS-DOS) are transparently accessible.
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.IP
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Windows appear in name spaces on a par with files and processes.
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.IP
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A historical file system allows one to navigate
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the archival file system in time as well as in space;
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backup files are always at hand.
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.IP
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A debugger can handle simultaneously active processes
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on disparate kinds of hardware.
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.PP
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The character set of Plan 9 is Unicode, which
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covers most of the world's major scripts.
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The system has its own programming languages:
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a dialect of C with simple inheritance, a simplified shell,
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and a CSP-like concurrent language, Alef.
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An ANSI-POSIX emulator (APE) admits unreconstructed Unix code.
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.PP
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Plan 9 is the work of many people.
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The protocol was begun by Ken Thompson; naming
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was integrated by Rob Pike and networking by Dave Presotto.
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Phil Winterbottom simplified the management of name spaces
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and re-engineered the system.
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They were joined by Tom Killian, Jim McKie, and Howard Trickey in
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bringing the system up on various machines and making
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device drivers.
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Thompson made the C compiler;
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Pike, window systems;
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Tom Duff, the shell and raster graphics;
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Winterbottom, Alef;
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Trickey, Duff, and Andrew Hume, APE.
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Bob Flandrena ported a myriad of
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programs to Plan 9.
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Other contributors include
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Alan Berenbaum,
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Lorinda Cherry,
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Bill Cheswick,
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Sean Dorward,
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David Gay,
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Paul Glick,
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Eric Grosse,
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John Hobby,
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Gerard Holzmann,
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Brian Kernighan,
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Bart Locanthi,
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Doug McIlroy,
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Judy Paone,
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Sean Quinlan,
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Bob Restrick,
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Dennis Ritchie,
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Bjarne Stroustrup,
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and
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Cliff Young.
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.PP
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Plan 9 is made available as is, without formal support, but
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substantial comments or contributions may be communicated to
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the authors.
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.sp
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.in 4i
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Doug McIlroy
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.br
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March, 1995
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