Provided by: groff_1.21-6_i386 bug

NAME

       roff - concepts and history of roff typesetting

DESCRIPTION

       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 extensions.

       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.

HISTORY

       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 <http://
       www.multicians.org>.  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 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.

       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.

   Availability
       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 <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.

       An alternative is Gunnar Ritter's Heirloom Documentation Tools <http://
       heirloom.sf.net>  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.

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.

              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 formulae.
              pic      for drawing diagrams.
              refer    for bibliographic references.
              soelim   for including macro files from standard locations.
              chem     for drawing chemical formulae.

       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.

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
       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.

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:

              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.

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

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

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

       o      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.

       o      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.

       o      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.

       o      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.

       o      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
              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.

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.

       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://
              www.bell-labs.com/>  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  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   <http://cm.bell-
              labs.com/cm/cs/cstr/54.ps.gz>; Bell Labs, 1976; revised by Brian
              Kernighan, 1992.

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

       [CSTR #116]
              Brian W. Kernighan, PIC - A Graphics  Language  for  Typesetting
              <http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz>;    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  Chemistry   <http://cm.bell-labs.com/cm/cs/cstr/122.ps.gz>;
              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, 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 <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>.