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       roff - concepts and history of roff typesetting


       roff  is  the  general  name for a set of text formatting programs, known under names like
       troff, nroff, ditroff,  groff,  etc.   A  roff  system  consists  of  an  extensible  text
       formatting  language  and  a  set  of  programs  for printing and converting to other text
       formats.  Unix-like operating systems distribute a roff system as a core package.

       The most common roff system today is the free software implementation GNU roff,  groff(1).
       groff  implements  the  look-and-feel  and  functionality  of  its  ancestors,  with  many

       The ancestry of roff is described in section HISTORY.  In this  document,  the  term  roff
       always  refers  to the general class of roff programs, not to the roff command provided in
       early UNIX systems.

       In spite of its age, roff is in wide use today, for example,  the  manual  pages  on  UNIX
       systems  (man  pages), many software books, system documentation, standards, and corporate
       documents are written in roff.  The roff output for text devices is still  unmatched,  and
       its  graphical  output  has  the  same  quality as other free type-setting programs and is
       better than some of the commercial systems.

       roff is used to format UNIX manual pages,  (or  man  pages),  the  standard  documentation
       system on many UNIX-derived operating systems.

       This  document  describes  the  history  of the development of the roff system; some usage
       aspects common to all roff versions, details on the roff pipeline, which is usually hidden
       behind  front-ends like groff(1); a general overview of the formatting language; some tips
       for editing roff files; and many pointers to further readings.


       Document formatting by computer dates back to  the  1960s.   The  roff  system  itself  is
       intimately  connected  to  the Unix operating system, but its roots go back to the earlier
       operating systems CTSS and Multics.

   The Predecessor RUNOFF
       roff's ancestor RUNOFF was written in the MAD language by Jerry Saltzer for the Compatible
       Time  Sharing System (CTSS), a project of the Massachusetts Institute of Technology (MIT),
       in 1963 and 1964 – note that CTSS commands were all uppercase.

       In 1965, MIT's Project MAC teamed with  Bell  Telephone  Laboratories  (BTL)  and  General
       Electric to begin the Multics system ⟨⟩.  A command called runoff
       was written for Multics in the late 60s in the BCPL language, by Bob Morris, Doug McIlroy,
       and other members of the Multics team.

       Like  its  CTSS  ancestor,  Multics  runoff formatted an input file consisting of text and
       command lines; commands began with a period and  were  two  letters.   Output  from  these
       commands  was  to  terminal  devices  such as IBM Selectric terminals.  Multics runoff had
       additional features added, such as the ability to do two-pass formatting;  it  became  the
       main format for Multics documentation and text processing.

       BCPL  and runoff were ported to the GCOS system at Bell Labs when BTL left the development
       of Multics.

   The Classical nroff/troff System
       At BTL, there was a need to drive the Graphic Systems CAT typesetter, a  graphical  output
       device  from  a  PDP-11 computer running Unix.  As runoff was too limited for this task it
       was further developed into a more powerful text formatting system by  Joseph  F.  Ossanna,
       who already programmed several runoff ports.

       The name runoff was shortened to roff.  The greatly enlarged language of Ossanna's version
       already included all elements of a full roff system.   All  modern  roff  systems  try  to
       implement  compatibility  to  this system.  So Joe Ossanna can be called the father of all
       roff systems.

       This first roff system had three formatter programs.

       troff  (typesetter roff) generated a graphical output for the CAT typesetter as  its  only

       nroff  produced text output suitable for terminals and line printers.

       roff   was  the  reimplementation  of the former runoff program with its limited features;
              this program was abandoned in later versions.  Today, the  name  roff  is  used  to
              refer to a troff/nroff system as a whole.

       Ossanna's  first version was written in the PDP-11 assembly language and released in 1973.
       Brian Kernighan joined the roff development by rewriting it in the C programming language.
       The C version was released in 1975.

       The  syntax  of  the formatting language of the nroff/troff programs was documented in the
       famous Troff User's Manual [CSTR #54], first published in 1976, with further revisions  up
       to  1992  by  Brian Kernighan.  This document is the specification of the classical troff.
       All later roff systems tried to establish compatibility with this specification.

       After Ossanna's death in 1977, Kernighan went on  with  developing  troff.   In  the  late
       1970s,  Kernighan  equipped  troff  with  a general interface to support more devices, the
       intermediate output format, and the postprocessor system.  This completed the structure of
       a  roff  system  as  it  is  still  in  use today; see section USING ROFF.  In 1979, these
       novelties were described in the paper [CSTR #97].  This new troff version is the basis for
       all  existing  newer  troff  systems,  including  groff.   On  some  systems,  this device
       independent troff got a binary of its own, called ditroff(7).  All modern  troff  programs
       already provide the full ditroff capabilities automatically.

       The  source  code  of  both the ancient Unix and classical troff weren't available for two
       decades.  Meanwhile, it is accessible again (on-line) for non-commercial use, cf.  section
       SEE ALSO.

   Free roff
       The  most  important  free  roff project was the GNU implementation of troff, written from
       scratch by James Clark and put under the GNU Public License ⟨⟩.
       It was called groff (GNU roff).  See groff(1) for an overview.

       The  groff  system  is still actively developed.  It is compatible to the classical troff,
       but many extensions were added.  It is the first roff system that is available  on  almost
       all  operating  systems  –  and  it  is free.  This makes groff the de-facto roff standard

       An alternative is Gunnar Ritter's Heirloom  Documentation  Tools  ⟨⟩
       project, started in 2005, which provides enhanced versions of the various roff tools found
       in the OpenSolaris and Plan 9 operating systems, now available under free licenses.


       Most people won't even notice that they are actually using roff.  When you read  a  system
       manual  page  (man  page) roff is working in the background.  roff documents can be viewed
       with a native viewer called xditview(1x), a standard program of the X window distribution,
       see X(7x).  But using roff explicitly isn't difficult either.

       Some  roff  implementations  provide  wrapper  programs  that make it easy to use the roff
       system on the shell command line.  For  example,  the  GNU  roff  implementation  groff(1)
       provides  command  line  options  to  avoid  the  long command pipes of classical troff; a
       program grog(1) tries to guess from the document which arguments should be used for a  run
       of groff; people who do not like specifying command line options should try the groffer(1)
       program for graphically displaying groff files and man pages.

   The roff Pipe
       Each roff system consists of preprocessors, roff formatter programs, and a set  of  device
       postprocessors.   This  concept makes heavy use of the piping mechanism, that is, a series
       of programs is called one after the other, where the output of each program in  the  queue
       is taken as the input for the next program.

              cat file | ... | preproc | ... | troff options | postproc

       The preprocessors generate roff code that is fed into a roff formatter (e.g. troff), which
       in turn generates intermediate output that is fed into a device postprocessor program  for
       printing or final output.

       All  of  these  parts  use  programming  languages  of their own; each language is totally
       unrelated to the other parts.  Moreover,  roff  macro  packages  that  were  tailored  for
       special purposes can be included.

       Most  roff  documents use the macros of some package, intermixed with code for one or more
       preprocessors, spiced with some elements from the plain roff language.  The full power  of
       the roff formatting language is seldom needed by users; only programmers of macro packages
       need to know about the gory details.

       A roff preprocessor is any program that generates  output  that  syntactically  obeys  the
       rules  of  the  roff formatting language.  Each preprocessor defines a language of its own
       that is translated into roff code  when  run  through  the  preprocessor  program.   Parts
       written  in these languages may be included within a roff document; they are identified by
       special roff requests or macros.  Each document that is enhanced by preprocessor code must
       be  run  through  all  corresponding  preprocessors  before it is fed into the actual roff
       formatter program, for the formatter  just  ignores  all  alien  code.   The  preprocessor
       programs extract and transform only the document parts that are determined for them.

       There  are a lot of free and commercial roff preprocessors.  Some of them aren't available
       on each system, but there is a small set  of  preprocessors  that  are  considered  as  an
       integral part of each roff system.  The classical preprocessors are

              tbl      for tables.
              eqn      for mathematical formulæ.
              pic      for drawing diagrams.
              refer    for bibliographic references.
              soelim   for including macro files from standard locations.
              chem     for drawing chemical formulæ.

       Other known preprocessors that are not available on all systems include

              grap   for constructing graphical elements.
              grn    for including gremlin(1) pictures.

   Formatter Programs
       A  roff  formatter  is  a  program  that  parses  documents written in the roff formatting
       language or uses some of the roff macro packages.  It generates intermediate output, which
       is  intended  to  be  fed  into  a single device postprocessor that must be specified by a
       command-line option to the formatter program.  The documents must have  been  run  through
       all necessary preprocessors before.

       The  output  produced  by  a  roff  formatter  is represented in yet another language, the
       intermediate output format  or  troff  output.   This  language  was  first  specified  in
       [CSTR  #97];  its  GNU  extension  is documented in groff_out(5).  The intermediate output
       language is a kind of assembly language compared to the  high-level  roff  language.   The
       generated  intermediate  output is optimized for a special device, but the language is the
       same for every device.

       The roff formatter is the heart  of  the  roff  system.   The  traditional  roff  had  two
       formatters, nroff for text devices and troff for graphical devices.

       Often, the name troff is used as a general term to refer to both formatters.

   Devices and Postprocessors
       Devices  are  hardware  interfaces  like  printers,  text or graphical terminals, etc., or
       software interfaces such as a conversion into a different text or graphical format.

       A roff postprocessor is a program that transforms troff output into a form suitable for  a
       special device.  The roff postprocessors are like device drivers for the output target.

       For  each  device  there  is  a postprocessor program that fits the device optimally.  The
       postprocessor parses the generated intermediate output and generates device-specific  code
       that is sent directly to the device.

       The names of the devices and the postprocessor programs are not fixed because they greatly
       depend on the software and hardware abilities of the actual computer.   For  example,  the
       classical  devices mentioned in [CSTR #54] have greatly changed since the classical times.
       The old hardware doesn't exist any longer and the old  graphical  conversions  were  quite
       imprecise when compared to their modern counterparts.

       For  example,  the Postscript device post in classical troff had a resolution of 720 units
       per inch, while groff's ps device has 72000, a refinement of factor 100.

       Today the operating systems provide device drivers for most printer-like hardware,  so  it
       isn't necessary to write a special hardware postprocessor for each printer.


       Documents  using  roff  are  normal text files decorated by roff formatting elements.  The
       roff formatting language is quite powerful; it is almost a full programming  language  and
       provides  elements  to  enlarge  the  language.  With these, it became possible to develop
       macro packages that are tailored for special applications.  Such macro packages  are  much
       handier  than  plain  roff.   So  most people will choose a macro package without worrying
       about the internals of the roff language.

   Macro Packages
       Macro packages are collections of macros that are suitable to format  a  special  kind  of
       documents  in  a  convenient  way.   This  greatly  eases  the  usage  of roff.  The macro
       definitions of a package are kept in a file called name.tmac (classically  All
       tmac  files  are  stored in one or more directories at standardized positions.  Details on
       the naming of macro packages and their placement is found in groff_tmac(5).

       A macro package that is to be used in a document can be announced to the formatter by  the
       command  line  option -m, see troff(1), or it can be specified within a document using the
       file inclusion requests of the roff language, see groff(7).

       Famous classical macro packages are man for traditional  man  pages,  mdoc  for  BSD-style
       manual  pages;  the  macro sets for books, articles, and letters are me (probably from the
       first name of its creator  Eric  Allman),  ms  (from  Manuscript  Macros),  and  mm  (from
       Memorandum Macros).

   The roff Formatting Language
       The  classical  roff  formatting  language  is  documented  in  the  Troff  User's  Manual
       [CSTR #54].  The  roff  language  is  a  full  programming  language  providing  requests,
       definition  of  macros,  escape sequences, string variables, number or size registers, and
       flow controls.

       Requests are the predefined basic formatting commands similar to the commands at the shell
       prompt.   The user can define request-like elements using predefined roff elements.  These
       are then called macros.  A document writer will not  note  any  difference  in  usage  for
       requests or macros; both are written on a line on their own starting with a dot.

       Escape  sequences  are  roff elements starting with a backslash `\'.  They can be inserted
       anywhere, also in the midst of text in  a  line.   They  are  used  to  implement  various
       features,  including  the insertion of non-ASCII characters with \(, font changes with \f,
       in-line comments with \", the escaping of special control characters  like  \\,  and  many
       other features.

       Strings  are  variables  that  can store a string.  A string is stored by the .ds request.
       The stored string can be retrieved later by the \* escape sequence.

       Registers store numbers and sizes.  A register can be set with the  request  .nr  and  its
       value can be retrieved by the escape sequence \n.


       Manual  pages  (man  pages)  take  the  section number as a file name extension, e.g., the
       filename for this document is roff.7, i.e., it is kept in section 7 of the man pages.

       The classical macro packages take the package name as an extension,  e.g.  for  a
       document  using  the  me  macro  package, for mm, for ms, file.pic for pic
       files, etc.

       But there is no general naming scheme for roff documents, though for troff file is
       seen now and then.  Maybe there should be a standardization for the filename extensions of
       roff files.

       File name extensions can be very handy in conjunction with the less(1) pager.  It provides
       the  possibility to feed all input into a command-line pipe that is specified in the shell
       environment variable LESSOPEN.  This process is not well documented, so here an example:

              LESSOPEN='|lesspipe %s'

       where lesspipe is either a system supplied command or a shell script of your own.


       The best program for editing a roff document is  Emacs  (or  Xemacs),  see  emacs(1).   It
       provides  an nroff mode that is suitable for all kinds of roff dialects.  This mode can be
       activated by the following methods.

       When editing a file within Emacs the mode can be changed by typing `M-x nroff-mode', where
       M-x means to hold down the Meta key (or Alt) and hitting the x key at the same time.

       But  it  is  also possible to have the mode automatically selected when the file is loaded
       into the editor.

       •      The most general method is to include the following 3 comment lines at the  end  of
              the file.

                     .\" Local Variables:
                     .\" mode: nroff
                     .\" End:

       •      There  is  a  set  of  file  name  extensions,  e.g. the man pages that trigger the
              automatic activation of the nroff mode.

       •      Theoretically, it is possible to write the sequence

                     .\" -*- nroff -*-

              as the first line of a  file  to  have  it  started  in  nroff  mode  when  loaded.
              Unfortunately,  some  applications such as the man program are confused by this; so
              this is deprecated.

       All roff formatters provide automated line breaks and horizontal and vertical spacing.  In
       order to not disturb this, the following tips can be helpful.

       •      Never  include  empty  or  blank  lines in a roff document.  Instead, use the empty
              request (a line consisting of a dot only) or a line comment .\"  if  a  structuring
              element is needed.

       •      Never  start  a  line with whitespace because this can lead to unexpected behavior.
              Indented paragraphs can be constructed in a controlled way by roff requests.

       •      Start each sentence on a line of its own, for the spacing after a  dot  is  handled
              differently  depending  on whether it terminates an abbreviation or a sentence.  To
              distinguish both cases, do a line break after each sentence.

       •      To additionally use the auto-fill mode in Emacs, it is best to insert an empty roff
              request (a line consisting of a dot only) after each sentence.

       The following example shows how optimal roff editing could look.

              This is an example for a
              .I roff
              This is the next sentence in the same paragraph.
              This is a longer sentence stretching over several
              lines; abbreviations like `cf.' are easily
              identified because the dot is not followed by a
              line break.
              In the output, this will still go to the same

       Besides Emacs, some other editors provide nroff style files too, e.g. vim(1), an extension
       of the vi(1) program.


       There is a lot of documentation on roff.  The original papers on classical troff are still
       available, and all aspects of groff are documented in great detail.

   Internet sites
              The  historical troff site ⟨⟩ provides an overview and pointers
              to all historical aspects of roff.

              The Multics site ⟨⟩ contains a lot of information  on  the
              MIT  projects, CTSS, Multics, early Unix, including runoff; especially useful are a
              glossary and the many links to ancient documents.

       Unix Archive
              The Ancient Unixes Archive ⟨⟩ provides the source  code
              and some binaries of the ancient Unixes (including the source code of troff and its
              documentation) that were made public by Caldera since 2001, e.g. of the famous Unix
              version 7 for PDP-11 at the Unix V7 site ⟨

       Developers at AT&T Bell Labs
              Bell Labs Computing and Mathematical Sciences Research  ⟨⟩
              provides a search facility for tracking information on the early developers.

       Plan 9 The Plan 9 operating system ⟨⟩ by AT&T Bell Labs.

       runoff Jerry  Saltzer's  home page ⟨⟩
              stores some documents using the ancient RUNOFF formatting language.

       CSTR Papers
              The  Bell  Labs  CSTR  site  ⟨⟩  stores  the
              original  troff  manuals  (CSTR  #54,  #97, #114, #116, #122) and famous historical
              documents on programming.

       GNU roff
              The groff web  site  ⟨⟩  provides  the  free  roff
              implementation groff, the actual standard roff.

   Historical roff Documentation
       Many  classical  troff documents are still available on-line.  The two main manuals of the
       troff language are

       [CSTR #54]
              J.  F.  Ossanna,  Nroff/Troff  User's  Manual
    ⟩; Bell Labs, 1976; revised by Brian Kernighan, 1992.

       [CSTR #97]
              Brian  Kernighan,  A  Typesetter-independent  TROFF
              cstr/⟩, Bell Labs, 1981, revised March 1982.

       The “little language” roff papers are

       [CSTR #114]
              Jon L. Bentley and Brian W. Kernighan, GRAP  A  Language  for  Typesetting  Graphs⟩; Bell Labs, August 1984.

       [CSTR #116]
              Brian  W.  Kernighan,  PIC    A Graphics Language for Typesettinghttp://cm.bell-
    ⟩; Bell Labs, December 1984.

       [CSTR #122]
              J. L. Bentley, L.  W.  Jelinski,  and  B.  W.  Kernighan,  CHEM    A  Program  for
              Typesetting  Chemical  Structure Diagrams, Computers and Chemistryhttp://cm.bell-
    ⟩; Bell Labs, April 1986.

   Manual Pages
       Due to its complex structure, a full roff system has many man  pages,  each  describing  a
       single  aspect  of  roff.   Unfortunately,  there  is  no  general  naming  scheme for the
       documentation among the different roff implementations.

       In groff, the man page groff(1) contains a survey of all documentation available in groff.

       On other systems, you are on your own, but troff(1) might be a good starting point.


       Copyright (C) 2000,  2001,  2002,  2003,  2004,  2006,  2007,  2008,  2009  Free  Software
       Foundation, Inc.

       This  document  is distributed under the terms of the FDL (GNU Free Documentation License)
       version 1.3 or later.  You should have received a copy of the FDL on your  system,  it  is
       also available on-line at the GNU copyleft site ⟨⟩.

       This document is part of groff, the GNU roff distribution.  It was written by Bernd Warken
       ⟨⟩; it is maintained by Werner Lemberg ⟨⟩.