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NAME

       roff - concepts and history of roff typesetting

DESCRIPTION

       roff  is  the  general  name  for a set of type-setting programs, known
       under names like troff, nroff,  ditroff,  groff,  etc.   A  roff  type-
       setting system consists of an extensible text formatting language and a
       set of programs for printing and  converting  to  other  text  formats.
       Traditionally,  it  is  the  main text processing system of Unix; every
       Unix-like operating system still distributes a roff system  as  a  core
       package.

       The  most  common roff system today is the free software implementation
       GNU roff, groff(1).  The pre-groff implementations are referred  to  as
       classical  (dating  back  as long as 1973).  groff implements the look-
       and-feel and functionality of its classical  ancestors,  but  has  many
       extensions.   As  groff  is  the only roff system that is available for
       every (or almost  every)  computer  system  it  is  the  de-facto  roff
       standard today.

       In  some  ancient  Unix  systems,  there  was a binary called roff that
       implemented the even more  ancient  runoff  of  the  Multics  operating
       system,  cf.  section  HISTORY.   The functionality of this program was
       very restricted  even  in  comparison  to  ancient  troff;  it  is  not
       supported  any  longer.   Consequently, in this document, the term roff
       always refers to the general meaning of roff system, not to the ancient
       roff binary.

       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.

       The most popular application of roff is the concept of manual pages  or
       shortly  man  pages;  this is the standard documentation system on many
       operating systems.

       This document describes the historical facts around 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);  an  general  overview of the formatting language; some
       tips for editing roff files; and many pointers to further readings.

HISTORY

       The roff text processing system has a very long history, dating 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
       The  evolution  of  roff  is  intimately  related to the history of the
       operating systems.  Its predecessor runoff was written by Jerry Saltzer
       on  the CTSS operating system (Compatible Time Sharing System) as early
       as 1961.  When CTTS was further developed  into  the  operating  system
       Multics  〈http://www.multicians.org〉,  the  famous  predecessor of Unix
       from 1963, runoff became the main format  for  documentation  and  text
       processing.  Both operating systems could only be run on very expensive
       computers at that time, so they were mostly used in  research  and  for
       official and military tasks.

       The possibilities of the runoff language were quite limited as compared
       to modern roff.  Only text output was  possible  in  the  1960s.   This
       could  be  implemented  by a set of requests of length 2, many of which
       are  still  identically  used  in  roff.   The  language  was  modelled
       according  to  the habits of typesetting in the pre-computer age, where
       lines starting with a dot were used in manuscripts to denote formatting
       requests to the person who would perform the typesetting manually later
       on.

       The runoff program was written in the PL/1 language first, later on  in
       BCPL,  the  grandmother  of the C programming language.  In the Multics
       operating system, the help system was handled  by  runoff,  similar  to
       roff’s task to manage the Unix manual pages.  There are still documents
       written in the runoff language; for examples see Saltzer’s  home  page,
       cf. section SEE ALSO.

   The Classical nroff/troff System
       In  the 1970s, the Multics off-spring Unix became more and more popular
       because it could be run on affordable machines and was easily available
       for  universities at that time.  At MIT (the Massachusetts Institute of
       Technology), there was a need to drive the  Wang  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 Josef F. Osanna, a main
       developer of the Multics operating system  and  programmer  of  several
       runoff ports.

       The  name  runoff was shortened to roff.  The greatly enlarged language
       of Osanna’s concept included  already  all  elements  of  a  full  roff
       system.  All modern roff systems try to implement compatibility to this
       system.  So Joe Osanna 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 device.

       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 sytem as
              a whole.

       Osanna 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  Users  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 Osanna had died in 1977 by a heart-attack at the age of about 50,
       Kernighan  went  on  with  developing troff.  The next milestone was to
       equip 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.

   Commercialization
       A major degradation occurred when the easily available Unix 7 operating
       system  was  commercialized.   A  whole  bunch  of  divergent operating
       systems emerged, fighting each other with  incompatibilities  in  their
       extensions.   Luckily, the incompatibilities did not fight the original
       troff.  All of the different commercial roff systems made heavy use  of
       Osanna/Kernighan’s open source code and documentation, but sold them as
       “their” system — with only minor additions.

       The source code of both the ancient Unix and  classical  troff  weren’t
       available  for  two  decades.   Fortunately, Caldera bought SCO UNIX in
       2001.   In  the  following,  Caldera  made  the  ancient  source   code
       accessible on-line for non-commercial use, cf. section SEE ALSO.

   Free roff
       None  of  the  commercial  roff  systems  could  attain the status of a
       successor  for  the  general  roff  development.   Everyone  was   only
       interested  in  their  own  stuff.  This led to a steep downfall of the
       once excellent Unix operating system during the 1980s.

       As a counter-measure to the galopping commercialization, AT&T Bell Labs
       tried  to  launch  a rescue project with their Plan 9 operating system.
       It is freely available for non-commercial use, even  the  source  code,
       but  has a proprietary license that empedes the free development.  This
       concept is outdated, so Plan 9 was not accepted as a platform to bundle
       the main-stream development.

       The only remedy came from the emerging free operatings systems (386BSD,
       GNU/Linux, etc.) and software projects  during  the  1980s  and  1990s.
       These  implemented  the ancient Unix features and many extensions, such
       that the old experience is not lost.  In the  21st  century,  Unix-like
       systems  are again a major factor in computer industry — thanks to free
       software.

       The most important free roff project was the GNU port of troff, created
       by   James  Clark  and  put  under  the  GNU  Public  License  〈http://
       www.gnu.org/copyleft〉.  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 today.

USING ROFF

       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.

       sh# 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.

   Preprocessors
       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

       Other known preprocessors that are not available on all systems include

              chem    for drawing chemical formulæ.
              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, 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.

ROFF PROGRAMMING

       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 tmac.name).  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
       Users  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.

FILE NAME EXTENSIONS

       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.  file.me for a document using the me macro  package,  file.mm  for
       mm, file.ms for ms, file.pic for pic files, etc.

       But  there  is  no  general  naming  scheme  for roff documents, though
       file.tr 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:

       sh# LESSOPEN=’|lesspipe %s’

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

EDITING ROFF

       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 roff document.
              .
              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
              paragraph.

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

BUGS

       UNIX is a registered trademark of the Open  Group.   But  things  have
       improved considerably after Caldera had bought SCO UNIX in 2001.

SEE ALSO

       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
       troff.org
              The  historical  troff  site  〈http://www.troff.org〉 provides an
              overview and pointers to all historical aspects of  roff.   This
              web  site  is  under  construction;  once,  it will be the major
              source for roff history.

       Multics
              The Multics site 〈http://www.multicians.org〉 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  〈http://www.tuhs.org/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 〈http://www.tuhs.org/
              Archive/PDP-11/Trees/V7〉.

       Developers at AT&T Bell Labs
              Bell Labs Computing and Mathematical Sciences Research  〈http://
              cm.bell-labs.com/cm/index.html〉  provides  a search facility for
              tracking information on the early developers.

       Plan 9 The Plan 9 operating system 〈http://plan9.bell-labs.com〉 by AT&T
              Bell Labs.

       runoff Jerry   Saltzer’s   home  page  〈http://web.mit.edu/Saltzer/www/
              publications/pubs.html〉 stores some documents using the  ancient
              runoff formatting language.

       CSTR Papers
              The   Bell   Labs   CSTR   site  〈http://cm.bell-labs.com/cm/cs/
              cstr.html〉 stores the original troff  manuals  (CSTR  #54,  #97,
              #114,   #116,   #122)   and   famous   historical  documents  on
              programming.

       GNU roff
              The groff web site 〈http://www.gnu.org/software/groff〉  provides
              the free roff implementation groff, the actual standard roff.

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

       [CSTR #54]
              J.   F.   Osanna,    Nroff/Troff    Users    Manual    〈http://
              cm.bell-labs.com/cm/cs/54.ps〉; Bell Labs, 1976; revised by Brian
              Kernighan, 1992.

       [CSTR #97]
              Brian  Kernighan,  A   Typesetter-independent   TROFF   〈http://
              cm.bell-labs.com/cm/cs/97.ps〉,  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  Graphshttp://cm.bell-labs.com/cm/cs/114.ps〉; Bell
              Labs, August 1984.

       [CSTR #116]
              Brian W. Kernighan, PIC -- A Graphics Language  for  Typesettinghttp://cm.bell-labs.com/cm/cs/116.ps〉;   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-labs.com/cm/cs/122.ps〉; 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.

AUTHORS

       Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.

       This document is distributed under the  terms  of  the  FDL  (GNU  Free
       Documentation  License) version 1.1 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 〈http://www.gnu.org/copyleft/fdl.html〉.

       This  document  is  part  of  groff, the GNU roff distribution.  It was
       written by Bernd Warken 〈bwarken@mayn.de〉; it is maintained  by  Werner
       Lemberg 〈wl@gnu.org〉.