roff - concepts and history of roff typesetting
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 for-
mats. Traditionally, it is the main text processing system of Unix; every Unix-like oper-
ating 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 functional-
ity 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 sys-
tems (man pages), many software books, system documentation, standards, and corporate doc-
uments 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 lan-
guage; some tips for editing roff files; and many pointers to further readings.
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 sys-
tems 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 grand-
mother 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
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 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 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 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 sys-
tems, this device independent troff got a binary of its own, called ditroff(7). All mod-
ern troff programs already provide the full ditroff capabilities automatically.
A major degradation occurred when the easily available Unix 7 operating system was commer-
cialized. 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.
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-commer-
cial use, even the source code, but has a proprietary license that empedes the free devel-
opment. This concept is outdated, so Plan 9 was not accepted as a platform to bundle the
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 fea-
tures 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 soft-
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
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 sys-
tem 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 unre-
lated 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 writ-
ten in these languages may be included within a roff document; they are identified by spe-
cial 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 format-
ter program, for the formatter just ignores all alien code. The preprocessor programs ex-
tract 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 inte-
gral 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
Other known preprocessors that are not available on all systems include
chem for drawing chemical formulae.
grap for constructing graphical elements.
grn for including gremlin(1) pictures.
A roff formatter is a program that parses documents written in the roff formatting lan-
guage 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 neces-
sary preprocessors before.
The output produced by a roff formatter is represented in yet another language, the inter-
mediate 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 inter-
mediate output is optimized for a special device, but the language is the same for every
The roff formatter is the heart of the roff system. The traditional roff had two format-
ters, 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 soft-
ware 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 im-
precise 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.
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 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 defini-
tions 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 man-
ual 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
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, defini-
tion of macros, escape sequences, string variables, number or size registers, and flow
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 re-
quests 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 fea-
tures, 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
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 file-
name 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
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
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.
The best program for editing a roff document is Emacs (or Xemacs), see emacs(1). It pro-
vides an nroff mode that is suitable for all kinds of roff dialects. This mode can be ac-
tivated 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
.\" Local Variables:
.\" mode: nroff
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. Unfortunate-
ly, some applications such as the man program are confused by this; so this is deprecat-
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
o Never start a line with whitespace because this can lead to unexpected behavior. In-
dented 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 differ-
ently 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 re-
quest (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
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.
UNIX(R) is a registered trademark of the Open Group. But things have improved consider-
ably after Caldera had bought SCO UNIX in 2001.
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.
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.
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.
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/
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 devel-
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.
The Bell Labs CSTR site <http://cm.bell-labs.com/cm/cs/cstr.html> stores the origi-
nal troff manuals (CSTR #54, #97, #114, #116, #122) and famous historical documents
The groff web site <http://www.gnu.org/software/groff> provides the free roff im-
plementation groff, the actual standard roff.
Historical roff Documentation
Many classical documents are still available on-line. The two main manuals of the troff
J. F. Osanna, Nroff/Troff User's Manual <http://cm.bell-labs.com/cm/cs/54.ps>; Bell
Labs, 1976; revised by Brian Kernighan, 1992.
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
Jon L. Bentley and Brian W. Kernighan, GRAP -- A Language for Typesetting Graphs
<http://cm.bell-labs.com/cm/cs/114.ps>; Bell Labs, August 1984.
Brian W. Kernighan, PIC -- A Graphics Language for Typesetting <http://
cm.bell-labs.com/cm/cs/116.ps>; Bell Labs, December 1984.
J. L. Bentley, L. W. Jelinski, and B. W. Kernighan, CHEM -- A Program for Typeset-
ting Chemical Structure Diagrams, Computers and Chemistry <http://cm.bell-labs.com/
cm/cs/122.ps>; Bell Labs, April 1986.
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 documen-
tation 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 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
<email@example.com>; it is maintained by Werner Lemberg <firstname.lastname@example.org>.
Groff Version 1.18.1 Nov 2003 ROFF(7)