ROFF(7)		       Miscellaneous Information Manual		       ROFF(7)



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 con-
       sists  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 functional-
       ity of its ancestors, with many extensions.

       The  ancestry  of  roff is described in section HISTORY.	 In this docu-
       ment, the term roff always refers to the general	 class	of  roff  pro-
       grams, 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 documen-
       tation,	standards,  and	 corporate documents are written in roff.  The
       roff output for text devices is still unmatched, and its graphical out-
       put  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 sys-
       tem; 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 sys-
       tem 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	Massa-
       chusetts	 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 consist-
       ing  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 pow-
       erful  text  formatting	system	by Joseph F. Ossanna, who already pro-
       grammed 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 sys-
       tem.  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 type-
	      setter 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 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 pub-
       lished 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  postpro-
       cessor  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 ver-
       sions  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 back-
       ground.	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 lan-
       guage 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 syntacti-
       cally obeys the rules of the roff formatting language.  Each preproces-
       sor  defines  a	language  of its own that is translated into roff code
       when run through the preprocessor program.  Parts written in these lan-
       guages  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  for-
       matter  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 pre-
       processors 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 gener-
       ates  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 lan-
       guage was first specified in [CSTR #97]; its  GNU  extension  is	 docu-
       mented  in groff_out(5).	 The intermediate output language is a kind of
       assembly language compared to the high-level roff language.  The gener-
       ated  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  for-
       matters.

   Devices and Postprocessors
       Devices are hardware interfaces like printers, text or graphical termi-
       nals, etc., or software interfaces such as a conversion into a  differ-
       ent 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	 reso-
       lution  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 post-
       processor 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  lan-
       guage.	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 nam-
       ing 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  All-
       man), 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 lan-
       guage  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 ele-
       ments 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	exten-
       sion,  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 clas-
       sical troff are still available, and all aspects	 of  groff  are	 docu-
       mented 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/> pro-
	      vides 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 program-
	      ming.

       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 Docu-
       mentation 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  <groff-bernd.warken-72@web.de>; it is main-
       tained by Werner Lemberg <wl@gnu.org>.



Groff Version 1.22.2		7 February 2013			       ROFF(7)