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@@ -0,0 +1,2444 @@
+.ig
+groff_diff.7
+
+Last update : 14 Nov 2001
+
+This file is part of groff, the GNU roff type-setting system.
+
+Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+written by James Clark
+
+modified by Werner Lemberg <wl@gnu.org>
+            Bernd Warken <bwarken@mayn.de>
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being this .ig-section and AUTHOR, with no
+Front-Cover Texts, and with no Back-Cover Texts.
+
+A copy of the Free Documentation License is included as a file called
+FDL in the main directory of the groff source package.
+..
+.
+.\" --------------------------------------------------------------------
+.\" Setup
+.\" --------------------------------------------------------------------
+.
+.mso www.tmac
+.
+.\" define a string tx for the TeX logo
+.ie t .ds tx T\h'-.1667m'\v'.224m'E\v'-.224m'\h'-.125m'X
+.el   .ds tx TeX
+.
+.de TQ
+.br
+.ns
+.TP \\$1
+..
+.
+.\" Like TP, but if specified indent is more than half
+.\" the current line-length - indent, use the default indent.
+.de Tp
+.ie \\n(.$=0:((0\\$1)*2u>(\\n(.lu-\\n(.iu)) .TP
+.el .TP "\\$1"
+..
+.
+.\" Don't use .ne for TTY devices
+.de NE
+.if t .ne \\$1
+..
+.
+.
+.\" --------------------------------------------------------------------
+.\" Title
+.\" --------------------------------------------------------------------
+.
+.TH GROFF_DIFF @MAN7EXT@ "@MDATE@" "Groff Version @VERSION@"
+.SH NAME
+groff_diff \- differences between GNU troff and classical troff
+.
+.
+.\" --------------------------------------------------------------------
+.SH DESCRIPTION
+.\" --------------------------------------------------------------------
+.
+This manual page describes the language differences between
+.IR groff ,
+the GNU
+.I roff
+text processing system and the classical
+.I roff
+formatter of the free Unix\~7 of the 1970s, documented in the
+.I Troff User's Manual
+by
+.I Osanna
+and
+.IR Kernighan .
+.
+.P
+The section
+.I SEE ALSO
+gives pointers to both the classical
+.I roff
+and the modern
+.I groff
+documentation.
+.
+.P
+At the moment, this document is the place of the most actual documentation
+with the
+.I groff
+system.
+All novelties are first described here and will pervade into the other
+documents only at a later stage.
+This might be changed in the future.
+.
+.
+.\" --------------------------------------------------------------------
+.SH "NEW FEATURES"
+.\" --------------------------------------------------------------------
+.
+In this section, all additional features of
+.I groff
+compared to the classical Unix\~7
+.I troff
+are described in detail.
+.
+.
+.\" --------------------------------------------------------------------
+.SS Long names
+.\" --------------------------------------------------------------------
+.
+The names of number registers, fonts, strings/\:macros/\:diversions,
+special characters, and colors can be of any length.
+In escape sequences, additionally to the classical
+.BI ( xx
+construction for a two character name, you can use
+.BI [ xxx ]
+for a name of arbitrary length, for example in
+.
+.TP \w'\ef[xxx]'u+3n
+.BI \e[ xxx ]
+Print the special character called
+.IR xxx .
+.
+.TP
+.BI \ef[ xxx ]
+Set font
+.IR xxx .
+.
+.TP
+.BI \e*[ xxx ]
+Interpolate string
+.IR xxx .
+.
+.TP
+.BI \en[ xxx ]
+Interpolate number register
+.IR xxx .
+.
+.
+.\" --------------------------------------------------------------------
+.SS Fractional pointsizes
+.\" --------------------------------------------------------------------
+.
+A
+.I scaled point
+is equal to
+.B 1/sizescale
+points, where
+.B sizescale
+is specified in the
+.B DESC
+file (1 by default).
+There is a new scale indicator
+.B z
+that has the effect of multiplying by sizescale.
+Requests and escape sequences in troff interpret arguments that represent a
+pointsize as being in units of scaled points, but they evaluate each such
+argument using a default scale indicator of
+.BR z .
+Arguments treated in this way are the argument to the
+.B ps
+request, the third argument to the
+.B cs
+request, the second and fourth arguments to the
+.B tkf
+request, the argument to the
+.B \eH
+escape sequence, and those variants of the
+.B \es
+escape sequence that take a numeric expression as their argument.
+.
+.P
+For example, suppose sizescale is 1000; then a scaled point will be
+equivalent to a millipoint; the request
+.B .ps\~10.25
+is equivalent to
+.B .ps\~10.25z
+and so sets the pointsize to 10250 scaled points, which is equal to
+10.25 points.
+.
+.P
+The number register
+.B \en[.s]
+returns the pointsize in points as decimal fraction.
+There is also a new number register
+.B \en[.ps]
+that returns the pointsize in scaled points.
+.
+.P
+It would make no sense to use the
+.B z
+scale indicator in a numeric expression whose default scale indicator was
+neither
+.B u
+nor
+.BR z ,
+and so
+.B troff
+disallows this.
+Similarly it would make no sense to use a scaling indicator other than
+.B z
+or
+.B u
+in a numeric expression whose default scale indicator was
+.BR z ,
+and so
+.B troff
+disallows this as well.
+.
+.P
+There is also new scale indicator
+.B s
+which multiplies by the number of units in a scaled point.
+So, for example,
+.B \en[.ps]s
+is equal to
+.BR 1m .
+Be sure not to confuse the
+.B s
+and
+.B z
+scale indicators.
+.
+.
+.\" --------------------------------------------------------------------
+.SS Numeric expressions
+.\" --------------------------------------------------------------------
+.
+Spaces are permitted in a number expression within parentheses.
+.
+.P
+.B M
+indicates a scale of 100ths of an em.
+.B f
+indicates a scale of 65536 units, providing fractions for color
+definitions with
+.B defcolor
+request.
+For example, 0.5f = 32768u.
+.
+.TP
+.IB e1 >? e2
+The maximum of
+.I e1
+and
+.IR e2 .
+.
+.TP
+.IB e1 <? e2
+The minimum of
+.I e1
+and
+.IR e2 .
+.
+.TP
+.BI ( c ; e )
+Evaluate
+.I e
+using
+.I c
+as the default scaling indicator.
+If
+.I c
+is missing, ignore scaling indicators in the evaluation of
+.IR e .
+.
+.
+.\" --------------------------------------------------------------------
+.SS New escape sequences
+.\" --------------------------------------------------------------------
+.
+.TP
+.BI \eA' anything '
+This expands to
+.B 1
+or
+.B 0
+resp., depending on whether
+.I anything
+is or is not acceptable as the name of a string, macro, diversion, number
+register, environment, font, or color.
+It will return\~\c
+.B 0
+if
+.I anything
+is empty.
+This is useful if you want to lookup user input in some sort of associative
+table.
+.
+.TP
+.BI \eB' anything '
+This expands to
+.B 1
+or
+.B 0
+resp., depending on whether
+.I anything
+is or is not a valid numeric expression.
+It will return\~\c
+.B 0
+if
+.I anything
+is empty.
+.
+.TP
+.BI \eC' xxx '
+Typeset character named
+.IR xxx .
+Normally it is more convenient to use
+.BI \e[ xxx ]\fR.
+But
+.B \eC
+has the advantage that it is compatible with recent versions of
+.SM UNIX
+and is available in compatibility mode.
+.
+.TP
+.B \eE
+This is equivalent to an escape character, but it is not interpreted in
+copy-mode.
+For example, strings to start and end superscripting could be defined like
+this
+.
+.RS
+.IP
+\&.ds { \ev'\-.3m'\es'\eEn[.s]*6u/10u'
+.br
+\&.ds } \es0\ev'.3m'
+.
+.P
+The use of
+.B \eE
+ensures that these definitions will work even if
+.B \e*{
+gets interpreted in copy-mode (for example, by being used in a macro
+argument).
+.RE
+.
+.TP
+.BI \em x
+.TQ
+.BI \em( xx
+.TQ
+.BI \em[ xxx ]
+Set drawing color.
+.B \emP
+switches back to the previous color.
+.
+.TP
+.BI \eM x
+.TQ
+.BI \eM( xx
+.TQ
+.BI \eM[ xxx ]
+Set background color for filled objects drawn with the
+.BI \eD' .\|.\|. '
+commands.
+.B \eMP
+switches back to the previous color.
+.
+.TP
+.BI \eN' n '
+Typeset the character with code
+.I n
+in the current font.
+.I n
+can be any integer.
+Most devices only have characters with codes between 0 and 255.
+If the current font does not contain a character with that code, special
+fonts will
+.I not
+be searched.
+The
+.B \eN
+escape sequence can be conveniently used in conjunction with the
+.B char
+request, for example
+.
+.RS
+.IP
+.B
+\&.char \e[phone] \ef(ZD\eN'37'
+.RE
+.
+.IP
+The code of each character is given in the fourth column in the font
+description file after the
+.B charset
+command.
+It is possible to include unnamed characters in the font description file by
+using a name of
+.BR \-\-\- ;
+the
+.B \eN
+escape sequence is the only way to use these.
+.
+.TP
+.BI \eR' name\ \(+-n '
+This has the same effect as
+.
+.RS
+.IP
+.BI .nr\  name\ \(+-n
+.RE
+.
+.TP
+.BI \es( nn
+.TQ
+.BI \es\(+-( nn
+Set the point size to
+.I nn
+points;
+.I nn
+must be exactly two digits.
+.
+.TP
+.BI \es[\(+- n ]
+.TQ
+.BI \es\(+-[ n ]
+.TQ
+.BI \es'\(+- n '
+.TQ
+.BI \es\(+-' n '
+Set the point size to
+.I n
+scaled points;
+.I n
+is a numeric expression with a default scale indicator of\~\c
+.BR z .
+.
+.TP
+.BI \eV x
+.TQ
+.BI \eV( xx
+.TQ
+.BI \eV[ xxx ]
+Interpolate the contents of the environment variable
+.IR xxx ,
+as returned by
+.BR getenv (3).
+.B \eV
+is interpreted in copy-mode.
+.
+.TP
+.BI \eY x
+.TQ
+.BI \eY( xx
+.TQ
+.BI \eY[ xxx ]
+This is approximately equivalent to
+.BI \eX'\e*[ xxx ]'\fR.
+However the contents of the string or macro
+.I xxx
+are not interpreted; also it is permitted for
+.I xxx
+to have been defined as a macro and thus contain newlines (it is not
+permitted for the argument to
+.B \eX
+to contain newlines).
+The inclusion of newlines requires an extension to the UNIX troff output
+format, and will confuse drivers that do not know about this extension.
+.
+.TP
+.BI \eZ' anything '
+Print anything and then restore the horizontal and vertical position;
+.I anything
+may not contain tabs or leaders.
+.
+.TP
+.B \e$0
+The name by which the current macro was invoked.
+.
+The
+.B als
+request can make a macro have more than one name.
+.
+.TP
+.B \e$*
+In a macro, the concatenation of all the arguments separated by spaces.
+.
+.TP
+.B \e$@
+In a macro, the concatenation of all the arguments with each surrounded by
+double quotes, and separated by spaces.
+.
+.TP
+.BI \e$( nn
+.TQ
+.BI \e$[ nnn ]
+In a macro, this gives the
+.IR nn -th
+or
+.IR nnn -th
+argument.
+Macros can have an unlimited number of arguments.
+.
+.TP
+.BI \e? anything \e?
+When used in a diversion, this will transparently embed
+.I anything
+in the diversion.
+.I anything
+is read in copy mode.
+When the diversion is reread,
+.I anything
+will be interpreted.
+.I anything
+may not contain newlines; use
+.B \e!\&
+if you want to embed newlines in a diversion.
+The escape sequence
+.B \e?\&
+is also recognised in copy mode and turned into a single internal code; it
+is this code that terminates
+.IR anything .
+Thus
+.
+.RS
+.IP
+.NE 14v+\n(.Vu
+.ft B
+.nf
+\&.nr x 1
+\&.nf
+\&.di d
+\e?\e\e?\e\e\e\e?\e\e\e\e\e\e\e\enx\e\e\e\e?\e\e?\e?
+\&.di
+\&.nr x 2
+\&.di e
+\&.d
+\&.di
+\&.nr x 3
+\&.di f
+\&.e
+\&.di
+\&.nr x 4
+\&.f
+.fi
+.ft
+.RE
+.
+.IP
+will print\~\c
+.BR 4 .
+.
+.TP
+.B \e/
+This increases the width of the preceding character so that the spacing
+between that character and the following character will be correct if the
+following character is a roman character.
+.if t \{\
+.  nop For example, if an italic f is immediately followed by a roman right
+.  nop parenthesis, then in many fonts the top right portion of the f will
+.  nop overlap the top left of the right parenthesis producing \fIf\fR)\fR,
+.  nop which is ugly.
+.  nop Inserting
+.  B \e/
+.  nop produces
+.  ie \n(.g \fIf\/\fR)\fR
+.  el       \fIf\|\fR)\fR
+.  nop and avoids this problem.
+.\}
+It is a good idea to use this escape sequence whenever an italic character
+is immediately followed by a roman character without any intervening space.
+.
+.TP
+.B \e,
+This modifies the spacing of the following character so that the spacing
+between that character and the preceding character will correct if the
+preceding character is a roman character.
+.if t \{\
+.  nop For example, inserting
+.  B \e,
+.  nop between the parenthesis and the f changes
+.  nop \fR(\fIf\fR to
+.  ie \n(.g \fR(\,\fIf\fR.
+.  el       \fR(\^\fIf\fR.
+.\}
+It is a good idea to use this escape sequence whenever a roman
+character is immediately followed by an italic character without any
+intervening space.
+.
+.TP
+.B \e)
+Like
+.B \e&
+except that it behaves like a character declared with the
+.B cflags
+request to be transparent for the purposes of end-of-sentence recognition.
+.
+.TP
+.B \e~
+This produces an unbreakable space that stretches like a normal inter-word
+space when a line is adjusted.
+.
+.TP
+.B \e:
+This causes the insertion of a zero-width break point.
+It is equal to
+.B \e%
+but without insertion of a soft hyphen character.
+.
+.TP
+.B \e#
+Everything up to and including the next newline is ignored.
+This is interpreted in copy mode.
+It is like
+.B \e"
+except that
+.B \e"
+does not ignore the terminating newline.
+.
+.
+.\" --------------------------------------------------------------------
+.SS New requests
+.\" --------------------------------------------------------------------
+.
+.TP
+.BI .aln\  xx\ yy
+Create an alias
+.I xx
+for number register object named
+.IR yy .
+The new name and the old name will be exactly equivalent.
+If
+.I yy
+is undefined, a warning of type
+.B reg
+will be generated, and the request will be ignored.
+.
+.TP
+.BI .als\  xx\ yy
+Create an alias
+.I xx
+for request, string, macro, or diversion object named
+.IR yy .
+The new name and the old name will be exactly equivalent (it is similar to a
+hard rather than a soft link).
+If
+.I yy
+is undefined, a warning of type
+.B mac
+will be generated, and the request will be ignored.
+The
+.BR de ,
+.BR am ,
+.BR di ,
+.BR da ,
+.BR ds ,
+and
+.B as
+requests only create a new object if the name of the macro, diversion or
+string diversion is currently undefined or if it is defined to be a request;
+normally they modify the value of an existing object.
+.
+.TP
+.BI .am1\  xx\ yy
+Similar to
+.BR .am , 
+but compatibility mode is switched off during execution.
+On entry, the current compatibility mode is saved and restored at exit.
+.
+.TP
+.BI .asciify\  xx
+This request `unformats' the diversion
+.I xx
+in such a way that
+.SM ASCII
+and space characters (and some escape sequences) that were formatted and
+diverted into
+.I xx
+will be treated like ordinary input characters when
+.I xx
+is reread.
+Useful for diversions in conjunction with the
+.B .writem
+request.
+It can be also used for gross hacks; for example, this
+.
+.RS
+.IP
+.NE 7v+\n(.Vu
+.ft B
+.nf
+\&.tr @.
+\&.di x
+\&@nr n 1
+\&.br
+\&.di
+\&.tr @@
+\&.asciify x
+\&.x
+.fi
+.RE
+.
+.IP
+will set register\~\c
+.B n
+to\~1.
+Note that glyph information (font, font size, etc.) is not preserved; use
+.B .unformat
+instead.
+.
+.TP
+.B .backtrace
+Print a backtrace of the input stack on stderr.
+.
+.TP
+.BI .blm\  xx
+Set the blank line macro to
+.IR xx .
+If there is a blank line macro, it will be invoked when a blank line
+is encountered instead of the usual troff behaviour.
+.
+.TP
+.BI .box\  xx
+.TQ
+.BI .boxa\  xx
+These requests are similar to the
+.B di
+and
+.B da
+requests with the exception that a partially filled line will not become
+part of the diversion (i.e., the diversion always starts with a new line)
+but restored after ending the diversion, discarding the partially filled
+line which possibly comes from the diversion.
+.
+.TP
+.B .break
+Break out of a while loop.
+See also the
+.B while
+and
+.B continue
+requests.
+Be sure not to confuse this with the
+.B br
+request.
+.
+.TP
+.B .brp
+This is the same as
+.BR \ep .
+.
+.TP
+.BI .cflags\  n\ c1\ c2\|.\|.\|.
+Characters
+.IR c1 ,
+.IR c2 ,\|.\|.\|.
+have properties determined by
+.IR n ,
+which is ORed from the following:
+.
+.RS
+.IP 1
+The character ends sentences (initially characters
+.B .?!\&
+have this property).
+.
+.IP 2
+Lines can be broken before the character (initially no characters have this
+property); a line will not be broken at a character with this property
+unless the characters on each side both have non-zero hyphenation codes.
+.
+.IP 4
+Lines can be broken after the character (initially characters
+.B \-\e(hy\e(em
+have this property); a line will not be broken at a character with this
+property unless the characters on each side both have non-zero hyphenation
+codes.
+.
+.IP 8
+The character overlaps horizontally (initially characters
+.B \e(ul\e(rn\e(ru
+have this property);
+.
+.IP 16
+The character overlaps vertically (initially character
+.B \e(br
+has this property);
+.
+.IP 32
+An end-of-sentence character followed by any number of characters with
+this property will be treated as the end of a sentence if followed by
+a newline or two spaces; in other words the character is transparent
+for the purposes of end-of-sentence recognition; this is the same as
+having a zero space factor in \*(tx (initially characters
+.B \(dq')]*\e(dg\e(rq
+have this property).
+.RE
+.
+.TP
+.BI .char\  c\ string
+Define character
+.I c
+to be
+.IR string .
+Every time character
+.I c
+needs to be printed,
+.I string
+will be processed in a temporary environment and the result will be wrapped
+up into a single object.
+Compatibility mode will be turned off and the escape character will be set
+to
+.B \e
+while
+.I string
+is being processed.
+Any emboldening, constant spacing or track kerning will be applied to this
+object rather than to individual characters in
+.IR string .
+A character defined by this request can be used just like a normal character
+provided by the output device.
+In particular other characters can be translated to it with the
+.B tr
+request; it can be made the leader character by the
+.B lc
+request; repeated patterns can be drawn with the character using the
+.B \el
+and
+.B \eL
+escape sequences; words containing the character can be hyphenated
+correctly, if the
+.B hcode
+request is used to give the character a hyphenation code.
+There is a special anti-recursion feature: use of character within the
+character's definition will be handled like normal characters not defined
+with
+.BR char .
+A character definition can be removed with the
+.B rchar
+request.
+.
+.TP
+.BI .chop\  xx
+Chop the last character off macro, string, or diversion
+.IR xx .
+This is useful for removing the newline from the end of diversions that are
+to be interpolated as strings.
+.
+.TP
+.BI .close\  stream
+Close the stream named
+.IR stream ;
+.I stream
+will no longer be an acceptable argument to the
+.B write
+request.
+See the
+.B open
+request.
+.
+.TP
+.B .continue
+Finish the current iteration of a while loop.
+See also the
+.B while
+and
+.B break
+requests.
+.
+.TP
+.BI .cp\  n
+If
+.I n
+is non-zero or missing, enable compatibility mode, otherwise disable it.
+In compatibility mode, long names are not recognised, and the
+incompatibilities caused by long names do not arise.
+.
+.TP
+.BI .defcolor\  xxx\ scheme\ color_components
+Define color.
+.I scheme
+can be one of the following values:
+.B rgb
+(three components),
+.B cym
+(three components),
+.B cmyk
+(four components), and
+.B gray
+or
+.B grey
+(one component).
+.
+Color components can be given either as a hexadecimal string or as positive
+decimal integers in the range 0-65535.
+A hexadecimal string contains all color components concatenated; it must
+start with either
+.B #
+or
+.BR ## .
+The former specifies hex values in the range 0-255 (which are internally
+multiplied by\~257), the latter in the range 0-65535.
+Examples: #FFC0CB (pink), ##ffff0000ffff (magenta).
+A new scaling indicator\~\c
+.B f
+has been introduced which multiplies its value by 65536; this makes it
+convenient to specify color components as fractions in the range 0 to\~1.
+Example:
+.
+.RS
+.IP
+.B
+\&.defcolor darkgreen rgb 0.1f 0.5f 0.2f
+.RE
+.
+.IP
+Note that
+.B f
+is the default scaling indicator for the
+.B defcolor
+request, thus the above statement is equivalent to
+.
+.RS
+.IP
+.B
+\&.defcolor darkgreen rgb 0.1 0.5 0.2
+.RE
+.
+.TP
+.BI .dei\  xx\ yy
+Define macro indirectly.
+.
+The following example
+.
+.RS
+.IP
+.NE 2v+\n(.Vu
+.ft B
+.nf
+\&.ds xx aa
+\&.ds yy bb
+\&.dei xx yy
+.fi
+.RE
+.
+.IP
+is equivalent to
+.
+.RS
+.IP
+.B
+\&.de aa bb
+.RE
+.
+.TP
+.BI .de1\  xx\ yy
+Similar to
+.BR .de , 
+but compatibility mode is switched off during execution.
+On entry, the current compatibility mode is saved and restored at exit.
+.
+.TP
+.BI .do\  xxx
+Interpret
+.I .xxx
+with compatibility mode disabled.
+For example,
+.
+.RS
+.IP
+.B
+\&.do fam T
+.P
+would have the same effect as
+.
+.IP
+.B
+\&.fam T
+.P
+except that it would work even if compatibility mode had been enabled.
+Note that the previous compatibility mode is restored before any files
+sourced by
+.I xxx
+are interpreted.
+.RE
+.
+.TP
+.B .ecs
+Save current escape character.
+.
+.TP
+.B .ecr
+Restore escape character saved with
+.BR ecs .
+Without a previous call to
+.BR ecs ,
+.RB ` \e '
+will be the new escape character.
+.
+.TP
+.BI .evc\  xx
+Copy the contents of environment
+.I xx
+to the current environment.
+No pushing or popping of environments will be done.
+.
+.TP
+.BI .fam\  xx
+Set the current font family to
+.IR xx .
+The current font family is part of the current environment.
+If
+.I xx
+is missing, switch back to previous font family.
+See the description of the
+.B sty
+request for more information on font families.
+.
+.TP
+.BI .fspecial\  f\ s1\ s2\|.\|.\|.
+When the current font is
+.IR f ,
+fonts
+.IR s1 ,
+.IR s2 ,\|.\|.\|.
+will be special, that is, they will searched for characters not in the
+current font.
+Any fonts specified in the
+.B special
+request will be searched after fonts specified in the
+.B fspecial
+request.
+.
+.TP
+.BI .ftr\  f\ g
+Translate font
+.I f
+to
+.IR g .
+Whenever a font named
+.I f
+is referred to in an
+.B \ef
+escape sequence, or in the
+.BR ft ,
+.BR ul ,
+.BR bd ,
+.BR cs ,
+.BR tkf ,
+.BR special ,
+.BR fspecial ,
+.BR fp ,
+or
+.BR sty
+requests, font
+.I g
+will be used.
+If
+.I g
+is missing, or equal to
+.I f
+then font
+.I f
+will not be translated.
+.
+.TP
+.BI .hcode \ c1\ code1\ c2\ code2\|.\|.\|.
+Set the hyphenation code of character
+.I c1
+to
+.I code1
+and that of
+.I c2
+to
+.IR code2 .
+A hyphenation code must be a single input character (not a special
+character) other than a digit or a space.
+Initially each lower-case letter has a hyphenation code, which is itself,
+and each upper-case letter has a hyphenation code which is the lower case
+version of itself.
+See also the
+.B hpf
+request.
+.
+.TP
+.BI .hla\  lang
+Set the current hyphenation language to
+.IR lang .
+Hyphenation exceptions specified with the
+.B hw
+request and hyphenation patterns specified with the
+.B hpf
+request are both associated with the current hyphenation language.
+The
+.B hla
+request is usually invoked by the
+.B troffrc
+file.
+.
+.TP
+.BI .hlm\  n
+Set the maximum number of consecutive hyphenated lines to\~\c
+.IR n .
+If
+.I n
+is negative, there is no maximum.
+The default value is\~\-1.
+This value is associated with the current environment.
+Only lines output from an environment count towards the maximum associated
+with that environment.
+Hyphens resulting from
+.B \e%
+are counted; explicit hyphens are not.
+.
+.TP
+.BI .hpf\  file
+Read hyphenation patterns from
+.IR file ;
+this will be searched for in the same way that
+.IB name .tmac
+is searched for when the
+.BI \-m name
+option is specified.
+It should have the same format as the argument to the \epatterns primitive
+in \*(tx; the letters appearing in this file are interpreted as hyphenation
+codes.
+A
+.BR % \~\c
+character in the patterns file introduces a comment that continues to the
+end of the line.
+The set of hyphenation patterns is associated with the current language set
+by the
+.B hla
+request.
+The
+.B hpf
+request is usually invoked by the
+.B troffrc
+file.
+.
+.TP
+.BI .hym\  n
+Set the
+.I hyphenation margin
+to\~\c
+.IR n :
+when the current adjustment mode is not\~\c
+.BR b ,
+the line will not be hyphenated if the line is no more than
+.I n
+short.
+The default hyphenation margin is\~0.
+The default scaling indicator for this request is\~\c
+.IR m .
+The hyphenation margin is associated with the current environment.
+The current hyphenation margin is available in the
+.B \en[.hym]
+register.
+.
+.TP
+.BI .hys\  n
+Set the
+.I hyphenation space
+to\~\c
+.IR n :
+when the current adjustment mode is\~\c
+.B b
+don't hyphenate the line if the line can be justified by adding no more than
+.I n
+extra space to each word space.
+The default hyphenation space is\~0.
+The default scaling indicator for this request is\~\c
+.BR m .
+The hyphenation space is associated with the current environment.
+The current hyphenation space is available in the
+.B \en[.hys]
+register.
+.
+.TP
+.BI .kern\  n
+If
+.I n
+is non-zero or missing, enable pairwise kerning, otherwise disable it.
+.
+.TP
+.BI .length\  xx\ string
+Compute the length of
+.I string
+and return it in the number register
+.I xx
+(which is not necessarily defined before).
+.
+.TP
+.BI .linetabs\  n
+If
+.I n
+is non-zero or missing, enable line-tabs mode, otherwise disable it
+(which is the default).
+In line-tabs mode, tab distances are computed relative to the (current)
+output line.
+Otherwise they are taken relative to the input line.
+For example, the following
+.
+.RS
+.IP
+.NE 6v+\n(.Vu
+.ft B
+.nf
+\&.ds x a\et\ec
+\&.ds y b\et\ec
+\&.ds z c
+\&.ta 1i 3i
+\e*x
+\e*y
+\e*z
+.fi
+.RE
+.
+.IP
+yields
+.
+.RS
+.IP
+a         b         c
+.RE
+.
+.IP
+In line-tabs mode, the same code gives
+.
+.RS
+.IP
+a         b                   c
+.RE
+.
+.IP
+Line-tabs mode is associated with the current environment; the read-only
+number register
+.B \\en[.linetabs]
+is set to\~1 if in line-tabs mode, and 0 otherwise.
+.
+.TP
+.BI .mso\  file
+The same as the
+.B so
+request except that
+.I file
+is searched for in the same directories as macro files for the the
+.B \-m
+command line option.
+If the file name to be included has the form
+.IB name .tmac
+and it isn't found,
+.B mso
+tries to include
+.BI tmac. name
+instead and vice versa.
+.
+.TP
+.BI .nop \ anything
+Execute
+.IR anything .
+This is similar to `.if\ 1'.
+.
+.TP
+.B .nroff
+Make the
+.B n
+built-in condition true and the
+.B t
+built-in condition false.
+This can be reversed using the
+.B troff
+request.
+.
+.TP
+.BI .open\  stream\ filename
+Open
+.I filename
+for writing and associate the stream named
+.I stream
+with it.
+See also the
+.B close
+and
+.B write
+requests.
+.
+.TP 
+.BI .opena\  stream\ filename
+Like
+.BR open ,
+but if
+.I filename
+exists, append to it instead of truncating it.
+.
+.TP
+.B .pnr
+Print the names and contents of all currently defined number registers on
+stderr.
+.
+.TP
+.BI .psbb \ filename
+Get the bounding box of a PostScript image
+.IR filename .
+This file must conform to Adobe's Document Structuring Conventions; the
+command looks for a
+.B \%%%BoundingBox
+comment to extract the bounding box values.
+After a successful call, the coordinates (in PostScript units) of the lower
+left and upper right corner can be found in the registers
+.BR \en[llx] ,
+.BR \en[lly] ,
+.BR \en[urx] ,
+and
+.BR \en[ury] ,
+respectively.
+If some error has occurred, the four registers are set to zero.
+.
+.TP
+.BI .pso \ command
+This behaves like the
+.B so
+request except that input comes from the standard output of
+.IR command .
+.
+.TP
+.B .ptr
+Print the names and positions of all traps (not including input line
+traps and diversion traps) on stderr.
+.
+Empty slots in the page trap list are printed as well, because they
+can affect the priority of subsequently planted traps.
+.
+.TP
+.BI .rchar\  c1\ c2\|.\|.\|.
+Remove the definitions of characters
+.IR c1 ,
+.IR c2 ,\|.\|.\|.
+This undoes the effect of a
+.B char
+request.
+.
+.TP
+.B .return
+Within a macro, return immediately.
+No effect otherwise.
+.
+.TP
+.B .rj
+.TQ
+.BI .rj\  n
+Right justify the next
+.IR n \~\c
+input lines.
+Without an argument right justify the next input line.
+The number of lines to be right justified is available in the
+.B \en[.rj]
+register.
+This implicitly does
+.BR .ce \~0 .
+The
+.B ce
+request implicitly does
+.BR .rj \~0 .
+.
+.TP
+.BI .rnn \ xx\ yy
+Rename number register
+.I xx
+to
+.IR yy .
+.
+.TP
+.BI .shc\  c
+Set the soft hyphen character to
+.IR c .
+If
+.I c
+is omitted, the soft hyphen character will be set to the default
+.BR \e(hy .
+The soft hyphen character is the character which will be inserted when a
+word is hyphenated at a line break.
+If the soft hyphen character does not exist in the font of the character
+immediately preceding a potential break point, then the line will not be
+broken at that point.
+Neither definitions (specified with the
+.B char
+request) nor translations (specified with the
+.B tr
+request) are considered when finding the soft hyphen character.
+.
+.TP
+.BI .shift\  n
+In a macro, shift the arguments by
+.I n
+positions: argument\~\c
+.I i
+becomes argument
+.IR i \- n ;
+arguments 1 to\~\c
+.I n
+will no longer be available.
+If
+.I n
+is missing, arguments will be shifted by\~1.
+Shifting by negative amounts is currently undefined.
+.
+.TP
+.BI .special\  s1\ s2\|.\|.\|.
+Fonts
+.IR s1 ,
+.IR s2 ,
+are special and will be searched for characters not in the current
+font.
+.
+.TP
+.BI .sty\  n\ f
+Associate style\~\c
+.I f
+with font position\~\c
+.IR n .
+A font position can be associated either with a font or with a style.
+The current font is the index of a font position and so is also either a
+font or a style.
+When it is a style, the font that is actually used is the font the name of
+which is the concatenation of the name of the current family and the name of
+the current style.
+For example, if the current font is\~1 and font position\~1 is associated
+with style
+.B R
+and the current font family is\~\c
+.BR T ,
+then font
+.BR TR
+will be used.
+If the current font is not a style, then the current family is ignored.
+When the requests
+.BR cs ,
+.BR bd ,
+.BR tkf ,
+.BR uf ,
+or
+.B fspecial
+are applied to a style, then they will instead be applied to the member of
+the current family corresponding to that style.
+The default family can be set with the
+.B \-f
+option.
+The styles command in the
+.SM DESC
+file controls which font positions (if any) are initially associated
+with styles rather than fonts.
+.
+.TP
+.BI .substring\  xx\ n1\  [ n2 ]
+Replace the string in register
+.I xx
+with the substring defined by the indices
+.I n1
+and
+.IR n2 .
+The first character in the string has index one.
+If
+.I n2
+is omitted, it is taken to be equal to the string's length.
+If the index value
+.I n1
+or
+.I n2
+is negative or zero, it will be counted from the end of the string, going
+backwards:
+The last character has index\~0, the character before the last character has
+index\~-1, etc.
+.
+.TP
+.BI .tkf\  f\ s1\ n1\ s2\ n2
+Enable track kerning for font
+.IR f .
+When the current font is
+.I f
+the width of every character will be increased by an amount between
+.I n1
+and
+.IR n2 ;
+when the current point size is less than or equal to
+.I s1
+the width will be increased by
+.IR n1 ;
+when it is greater than or equal to
+.I s2
+the width will be increased by
+.IR n2 ;
+when the point size is greater than or equal to
+.I s1
+and less than or equal to
+.I s2
+the increase in width is a linear function of the point size.
+.
+.TP
+.BI .tm1\  string
+Similar to the
+.B tm
+request,
+.I string
+is read in copy mode and written on the standard error, but an initial
+double quote in
+.I string
+is stripped off to allow initial blanks.
+.
+.TP
+.BI .tmc\  string
+Similar to
+.BR tm1
+but without writing a final newline.
+.
+.TP
+.BI .trf\  filename
+Transparently output the contents of file
+.IR filename .
+Each line is output as it would be preceded by
+.BR \e! ;
+however, the lines are not subject to copy-mode interpretation.
+If the file does not end with a newline, then a newline will be added.
+For example, you can define a macro\~\c
+.I x
+containing the contents of file\~\c
+.IR f ,
+using
+.
+.RS
+.IP
+.NE 2v+\n(.Vu
+.ft B
+.nf
+\&.di x
+\&.trf f
+\&.di
+.fi
+.RE
+.
+.IP
+Unlike with the
+.B cf
+request, the file cannot contain characters such as
+.SM NUL
+that are not legal troff input characters.
+.
+.TP
+.B .trnt abcd
+This is the same as the
+.B tr
+request except that the translations do not apply to text that is
+transparently throughput into a diversion with
+.BR \e! .
+For example,
+.
+.RS
+.IP
+.nf
+.ft B
+\&.tr ab
+\&.di x
+\e!.tm a
+\&.di
+\&.x
+.fi
+.ft
+.RE
+.
+.IP
+will print\~\c
+.BR b ;
+if
+.B trnt
+is used instead of
+.B tr
+it will print\~\c
+.BR a .
+.
+.TP
+.B .troff
+Make the
+.B n
+built-in condition false, and the
+.B t
+built-in condition true.
+This undoes the effect of the
+.B nroff
+request.
+.
+.TP
+.BI .unformat\  xx
+This request `unformats' the diversion
+.IR xx .
+Contrary to the
+.B .asciify
+request, which tries to convert formatted elements of the diversion back to
+input tokens as much as possible,
+.B .unformat
+will only handle tabs and spaces between words (usually caused by spaces or
+newlines in the input) specially.
+The former are treated as if they were input tokens, and the latter are
+stretchable again.
+Note that the vertical size of lines is not preserved.
+Glyph information (font, font size, space width, etc.) is retained.
+Useful in conjunction with the
+.B .box
+and
+.B .boxa
+requests.
+.
+.TP
+.BI .vpt\  n
+Enable vertical position traps if
+.I n
+is non-zero, disable them otherwise.
+Vertical position traps are traps set by the
+.B wh
+or
+.B dt
+requests.
+Traps set by the
+.B it
+request are not vertical position traps.
+The parameter that controls whether vertical position traps are enabled is
+global.
+Initially vertical position traps are enabled.
+.
+.TP
+.BI .warn\  n
+Control warnings.
+.I n
+is the sum of the numbers associated with each warning that is to be
+enabled; all other warnings will be disabled.
+The number associated with each warning is listed in the `Warnings' section.
+For example,
+.B .warn\~0
+will disable all warnings, and
+.B .warn\~1
+will disable all warnings except that about missing characters.
+If
+.I n
+is not given, all warnings will be enabled.
+.
+.TP
+.BI .while \ c\ anything
+While condition\~\c
+.I c
+is true, accept
+.I anything
+as input;
+.IR c \~\c
+can be any condition acceptable to an
+.B if
+request;
+.I anything
+can comprise multiple lines if the first line starts with
+.B \e{
+and the last line ends with
+.BR \e} .
+See also the
+.B break
+and
+.B continue
+requests.
+.
+.TP
+.BI .write\  stream\ anything
+Write
+.I anything
+to the stream named
+.IR stream .
+.I stream
+must previously have been the subject of an
+.B open
+request.
+.I anything
+is read in copy mode;
+a leading\~\c
+.B \(dq
+will be stripped.
+.
+.TP
+.BI .writem\  stream\ xx
+Write the contents of the macro or string
+.I xx
+to the stream named
+.IR stream .
+.I stream
+must previously have been the subject of an
+.B open
+request.
+.I xx
+is read in copy mode.
+.
+.
+.\" --------------------------------------------------------------------
+.SS Extended requests
+.\" --------------------------------------------------------------------
+.
+.TP
+.BI .cf\  filename
+When used in a diversion, this will embed in the diversion an object which,
+when reread, will cause the contents of
+.I filename
+to be transparently copied through to the output.
+.
+In UNIX troff, the contents of
+.I filename
+is immediately copied through to the output regardless of whether there is a
+current diversion; this behaviour is so anomalous that it must be considered
+a bug.
+.
+.TP
+.BI .ev\  xx
+If
+.I xx
+is not a number, this will switch to a named environment called
+.IR xx .
+The environment should be popped with a matching
+.B ev
+request without any arguments, just as for numbered environments.
+There is no limit on the number of named environments; they will be created
+the first time that they are referenced.
+.
+.TP
+.BI .fp\  n\ f1\ f2
+The
+.B fp
+request has an optional third argument.
+This argument gives the external name of the font, which is used for finding
+the font description file.
+The second argument gives the internal name of the font which is used to
+refer to the font in troff after it has been mounted.
+If there is no third argument then the internal name will be used as the
+external name.
+This feature allows you to use fonts with long names in compatibility mode.
+.
+.TP
+.BI .ss\  m\ n
+When two arguments are given to the
+.B ss
+request, the second argument gives the
+.IR "sentence space size" .
+If the second argument is not given, the sentence space size will be the
+same as the word space size.
+Like the word space size, the sentence space is in units of one twelfth of
+the spacewidth parameter for the current font.
+Initially both the word space size and the sentence space size are\~12.
+Contrary to UNIX troff, GNU troff handles this request in nroff mode also; a
+given value is then rounded down to the nearest multiple of\~12.
+The sentence space size is used in two circumstances:
+If the end of a sentence occurs at the end of a line in fill mode, then both
+an inter-word space and a sentence space will be added; if two spaces follow
+the end of a sentence in the middle of a line, then the second space will be
+a sentence space.
+Note that the behaviour of UNIX troff will be exactly that exhibited by GNU
+troff if a second argument is never given to the
+.B ss
+request.
+In GNU troff, as in UNIX troff, you should always follow a sentence with
+either a newline or two spaces.
+.
+.TP
+.BI .ta\  n1\ n2\|.\|.\|.nn \ T\  r1\ r2\|.\|.\|.\|rn
+Set tabs at positions
+.IR n1 ,
+.IR n2 ,\|.\|.\|.\|,
+.I nn
+and then set tabs at
+.IR nn + r1 ,
+.IR nn + r2 ,\|.\|.\|.\|.\|,
+.IR nn + rn
+and then at
+.IR nn + rn + r1 ,
+.IR nn + rn + r2 ,\|.\|.\|.\|,
+.IR nn + rn + rn ,
+and so on.
+For example,
+.
+.RS
+.IP
+.B
+\&.ta T .5i
+.P
+will set tabs every half an inch.
+.RE
+.
+.
+.\" --------------------------------------------------------------------
+.SS New number registers
+.\" --------------------------------------------------------------------
+.
+The following read-only registers are available:
+.
+.TP
+.B \en[.C]
+1\~if compatibility mode is in effect, 0\~otherwise.
+.
+.TP
+.B \en[.cdp]
+The depth of the last character added to the current environment.
+It is positive if the character extends below the baseline.
+.
+.TP
+.B \en[.ce]
+The number of lines remaining to be centered, as set by the
+.B ce
+request.
+.
+.TP
+.B \en[.cht]
+The height of the last character added to the current environment.
+It is positive if the character extends above the baseline.
+.
+.TP
+.B \en[.csk]
+The skew of the last character added to the current environment.
+The
+.I skew
+of a character is how far to the right of the center of a character the
+center of an accent over that character should be placed.
+.
+.TP
+.B \en[.ev]
+The name or number of the current environment.
+This is a string-valued register.
+.
+.TP
+.B \en[.fam]
+The current font family.
+This is a string-valued register.
+.
+.TP
+.B \en[.fp]
+The number of the next free font position.
+.
+.TP
+.B \en[.g]
+Always\~1.
+Macros should use this to determine whether they are running under GNU
+troff.
+.
+.TP
+.B \en[.hla]
+The current hyphenation language as set by the
+.B hla
+request.
+.
+.TP
+.B \en[.hlc]
+The number of immediately preceding consecutive hyphenated lines.
+.
+.TP
+.B \en[.hlm]
+The maximum allowed number of consecutive hyphenated lines, as set by the
+.B hlm
+request.
+.
+.TP
+.B \en[.hy]
+The current hyphenation flags (as set by the
+.B hy
+request).
+.
+.TP
+.B \en[.hym]
+The current hyphenation margin (as set by the
+.B hym
+request).
+.
+.TP
+.B \en[.hys]
+The current hyphenation space (as set by the
+.B hys
+request).
+.
+.TP
+.B \en[.in]
+The indent that applies to the current output line.
+.
+.TP
+.B \en[.int]
+Set to a positive value if last output line is interrupted (i.e., if
+it contains
+.IR \ec ).
+.
+.TP
+.B \en[.kern]
+1\~if pairwise kerning is enabled, 0\~otherwise.
+.
+.TP
+.B \en[.lg]
+The current ligature mode (as set by the
+.B lg
+request).
+.
+.TP
+.B \en[.linetabs]
+The current line-tabs mode (as set by the
+.B linetabs
+request).
+.
+.TP
+.B \en[.ll]
+The line length that applies to the current output line.
+.
+.TP
+.B \en[.lt]
+The title length as set by the
+.B lt
+request.
+.
+.TP
+.B \en[.ne]
+The amount of space that was needed in the last
+.B ne
+request that caused a trap to be sprung.
+Useful in conjunction with the
+.B \en[.trunc]
+register.
+.
+.TP
+.B \en[.ns]
+1\~if no-space mode is active, 0\~otherwise.
+.
+.TP
+.B \en[.pn]
+The number of the next page, either the value set by a
+.B pn
+request, or the number of the current page plus\~1.
+.
+.TP
+.B \en[.ps]
+The current pointsize in scaled points.
+.
+.TP
+.B \en[.psr]
+The last-requested pointsize in scaled points.
+.
+.TP
+.B \en[.rj]
+The number of lines to be right-justified as set by the
+.B rj
+request.
+.
+.TP
+.B \en[.sr]
+The last requested pointsize in points as a decimal fraction.
+This is a string-valued register.
+.
+.TP
+.B \en[.tabs]
+A string representation of the current tab settings suitable for use as an
+argument to the
+.B ta
+request.
+.
+.TP
+.B \en[.trunc]
+The amount of vertical space truncated by the most recently sprung vertical
+position trap, or, if the trap was sprung by a
+.B ne
+request, minus the amount of vertical motion produced by the
+.B ne
+request.
+In other words, at the point a trap is sprung, it represents the difference
+of what the vertical position would have been but for the trap, and what the
+vertical position actually is.
+Useful in conjunction with the
+.B \en[.ne]
+register.
+.
+.TP
+.B \en[.ss]
+.TQ
+.B \en[.sss]
+These give the values of the parameters set by the first and second
+arguments of the
+.B ss
+request.
+.
+.TP
+.B \en[.vpt]
+1\~if vertical position traps are enabled, 0\~otherwise.
+.
+.TP
+.B \en[.warn]
+The sum of the numbers associated with each of the currently enabled
+warnings.
+The number associated with each warning is listed in the `Warnings'
+subsection.
+.
+.TP
+.B \en[.x]
+The major version number.
+For example, if the version number is 1.03, then
+.B \en[.x]
+will contain\~1.
+.
+.TP
+.B \en[.y]
+The minor version number.
+For example, if the version number is 1.03, then
+.B \en[.y]
+will contain\~03.
+.
+.TP
+.B \en[.Y]
+The revision number of groff.
+.
+.TP
+.B \en[llx]
+.TQ
+.B \en[lly]
+.TQ
+.B \en[urx]
+.TQ
+.B \en[ury]
+These four registers are set by the
+.B \&.psbb
+request and contain the bounding box values (in PostScript units) of a given
+PostScript image.
+.
+.P
+The following read/write registers are set by the
+.B \ew
+escape sequence:
+.
+.TP
+.B \en[rst]
+.TQ
+.B \en[rsb]
+Like the
+.B st
+and
+.B sb
+registers, but take account of the heights and depths of characters.
+.
+.TP
+.B \en[ssc]
+The amount of horizontal space (possibly negative) that should be added to
+the last character before a subscript.
+.
+.TP
+.B \en[skw]
+How far to right of the center of the last character in the
+.B \ew
+argument, the center of an accent from a roman font should be placed
+over that character.
+.
+.P
+Other available read/write number registers are:
+.
+.TP
+.B \en[c.]
+The current input line number.
+.B \en[.c]
+is a read-only alias to this register.
+.
+.TP
+.B \en[hp]
+The current horizontal position at input line.
+.
+.TP
+.B \en[systat]
+The return value of the system() function executed by the last
+.B sy
+request.
+.
+.TP
+.B \en[slimit]
+If greater than\~0, the maximum number of objects on the input stack.
+If less than or equal to\~0, there is no limit on the number of objects on
+the input stack.
+With no limit, recursion can continue until virtual memory is exhausted.
+.
+.TP
+.B \en[year]
+The current year.
+.
+Note that the traditional
+.B troff
+number register
+.B \en[yr]
+is the current year minus 1900.
+.
+.
+.\" --------------------------------------------------------------------
+.SS Miscellaneous
+.\" --------------------------------------------------------------------
+.
+.B @g@troff
+predefines a single (read/write) string-based register,
+.BR \e*(.T ,
+which contains the argument given to the
+.B -T
+command line option, namely the current output device (for example,
+.I latin1
+or
+.IR ascii ).
+Note that this is not the same as the (read-only) number register
+.B \en[.T]
+which is defined to be\~1 if
+.B troff
+is called with the
+.B -T
+command line option, and zero otherwise.
+This behaviour is different to UNIX troff.
+.
+.P
+Fonts not listed in the
+.SM DESC
+file are automatically mounted on the next available font position when they
+are referenced.
+If a font is to be mounted explicitly with the
+.B fp
+request on an unused font position, it should be mounted on the first unused
+font position, which can be found in the
+.B \en[.fp]
+register; although
+.B troff
+does not enforce this strictly, it will not allow a font to be mounted at a
+position whose number is much greater than that of any currently used
+position.
+.
+.P
+Interpolating a string does not hide existing macro arguments.
+Thus in a macro, a more efficient way of doing
+.
+.IP
+.BI . xx\  \e\e$@
+.P
+is
+.
+.IP
+.BI \e\e*[ xx ]\e\e  
+.
+.P
+If the font description file contains pairwise kerning information,
+characters from that font will be kerned.
+Kerning between two characters can be inhibited by placing a
+.B \e&
+between them.
+.
+.P
+In a string comparison in a condition, characters that appear at different
+input levels to the first delimiter character will not be recognised as the
+second or third delimiters.
+This applies also to the
+.B tl
+request.
+In a
+.B \ew
+escape sequence, a character that appears at a different input level to the
+starting delimiter character will not be recognised as the closing delimiter
+character.
+When decoding a macro argument that is delimited by double quotes, a
+character that appears at a different input level to the starting delimiter
+character will not be recognised as the closing delimiter character.
+The implementation of
+.B \e$@
+ensures that the double quotes surrounding an argument will appear the same
+input level, which will be different to the input level of the argument
+itself.
+In a long escape name
+.B ]
+will not be recognized as a closing delimiter except when it occurs at the
+same input level as the opening
+.BR ] .
+In compatibility mode, no attention is paid to the input-level.
+.
+.P
+There are some new types of condition:
+.
+.TP
+.BI .if\ r xxx
+True if there is a number register named
+.IR xxx .
+.
+.TP
+.BI .if\ d xxx
+True if there is a string, macro, diversion, or request named
+.IR xxx .
+.
+.TP
+.BI .if\ m xxx
+True if there is a color named
+.IR xxx .
+.
+.TP
+.BI .if\ c ch
+True if there is a character
+.IR ch
+available;
+.I ch
+is either an
+.SM ASCII
+character or a special character
+.BI \e( xx
+or
+.BI \e[ xxx ]\fR;
+the condition will also be true if
+.I ch
+has been defined by the
+.B char
+request.
+.
+.P
+The
+.B tr
+request can now map characters onto
+.BR \e~ .
+.
+.P
+It is now possible to have whitespace between the first and second dot (or
+the name of the ending macro) to end a macro definition.
+Example:
+.
+.IP
+.NE 6v+\n(.Vu
+.ft B
+.nf
+\&.de foo
+\&.  nop Hello, I'm `foo'.
+\&.  nop I will now define `bar'.
+\&.  de bar
+\&.    nop Hello, I'm `bar'.
+\&.  .
+\&..
+.fi
+.
+.
+.\" --------------------------------------------------------------------
+.SH Incompatibilities
+.\" --------------------------------------------------------------------
+.
+Long names cause some incompatibilities.
+.
+UNIX troff will interpret
+.
+.IP
+.B
+\&.dsabcd
+.
+.P
+as defining a string
+.B ab
+with contents
+.BR cd .
+Normally, GNU troff will interpret this as a call of a macro named
+.BR dsabcd .
+Also UNIX troff will interpret
+.B \e*[
+or
+.B \en[
+as references to a string or number register called
+.BR [ .
+In GNU troff, however, this will normally be interpreted as the start of a
+long name.
+In
+.I compatibility mode
+GNU troff will interpret these things in the traditional way.
+In compatibility mode, however, long names are not recognised.
+Compatibility mode can be turned on with the
+.B \-C
+command line option, and turned on or off with the
+.B cp
+request.
+The number register
+.B \en[.C]
+is\~1 if compatibility mode is on, 0\~otherwise.
+.
+.P
+GNU troff does not allow the use of the escape sequences
+.BR \e\e\e|\e^\e&\e}\e{\e (space) \e'\e`\e-\e_\e!\e%\ec
+in names of strings, macros, diversions, number registers, fonts or
+environments; UNIX troff does.
+The
+.B \eA
+escape sequence may be helpful in avoiding use of these escape sequences in
+names.
+.
+.P
+Fractional pointsizes cause one noteworthy incompatibility.
+In UNIX troff the
+.B ps 
+request ignores scale indicators and so
+.
+.IP
+.B .ps\ 10u
+.
+.P
+will set the pointsize to 10 points, whereas in GNU troff it will set the
+pointsize to 10 scaled points.
+.
+.P
+In GNU troff there is a fundamental difference between unformatted, input
+characters, and formatted, output characters.
+Everything that affects how an output character will be output is stored
+with the character; once an output character has been constructed it is
+unaffected by any subsequent requests that are executed, including
+.BR bd ,
+.BR cs ,
+.BR tkf ,
+.BR tr ,
+or
+.B fp
+requests.
+Normally output characters are constructed from input characters at the
+moment immediately before the character is added to the current output line.
+Macros, diversions and strings are all, in fact, the same type of object;
+they contain lists of input characters and output characters in any
+combination.
+An output character does not behave like an input character for the purposes
+of macro processing; it does not inherit any of the special properties that
+the input character from which it was constructed might have had.
+For example,
+.
+.IP
+.NE 4v+\n(.Vu
+.ft B
+.nf
+\&.di x
+\e\e\e\e
+\&.br
+\&.di
+\&.x
+.ft
+.fi
+.
+.P
+will print
+.B \e\e
+in GNU troff; each pair of input
+.BR \e s
+is turned into one output
+.B \e
+and the resulting output
+.BR \e s
+are not interpreted as escape characters when they are reread.
+UNIX troff would interpret them as escape characters when they were reread
+and would end up printing one
+.BR \e .
+The correct way to obtain a printable
+.B \e
+is to use the
+.B \ee
+escape sequence: this will always print a single instance of the current
+escape character, regardless of whether or not it is used in a diversion; it
+will also work in both GNU troff and UNIX troff.
+If you wish for some reason to store in a diversion an escape sequence that
+will be interpreted when the diversion is reread, you can either use the
+traditional
+.B \e!\&
+transparent output facility, or, if this is unsuitable, the new
+.B \e?\&
+escape sequence.
+.
+.
+.\" --------------------------------------------------------------------
+.SH AUTHOR
+.\" --------------------------------------------------------------------
+.
+Copyright (C) 1989, 2001 Free Software Foundation, Inc.
+.
+.P
+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
+.URL "GNU copyleft site" http://\:www.gnu.org/\:copyleft/\:fdl.html .
+.
+This document was written by James Clark, with modifications by
+.URL "Werner Lemberg" mailto:wl@gnu.org
+and
+.URL "Bernd Warken" mailto:bwarken@mayn.de
+.
+.P
+This document is part of
+.IR groff ,
+the GNU roff distribution.
+Formerly, the informations of this document were kept in the manual page
+.BR troff (@MAN1EXT@).
+Only the parts dealing with the language aspects of the different
+.I roff
+systems were carried over into this document.
+The
+.I troff
+command line options and warnings are still available in
+.BR @g@troff (@MAN1EXT@).
+.
+.
+.\" --------------------------------------------------------------------
+.SH "SEE ALSO"
+.\" --------------------------------------------------------------------
+.
+.TP
+.BR roff (@MAN7EXT@)
+An overview over
+.I groff
+and other
+.I roff
+systems, including pointers to further related documentation.
+.
+.TP
+.BR groff (@MAN7EXT@)
+A description of the
+.I groff
+language, including a short, but complete reference of all predefined
+requests, registers, and escapes of plain
+.IR groff .
+From the command line, this is called by
+.BR man\~7\~groff .
+.
+.P
+The
+.I groff info
+.IR file ,
+cf.\&
+.BR info (@MAN1EXT@),
+presents all groff documentation within a single document.
+.
+.P
+The classical
+.I troff
+documentation is available on-line at
+.URL "Bell Labs CSTR site" http://\:cm.bell-labs.com/\:cm/\:cs/\:cstr.html .
+This includes as
+.I CSTR #54
+the
+.I Nroff/\:Troff User's Manual
+by
+.I J. F. Osanna
+of 1976 in the revision of
+.I Brian Kernighan
+of 1992, being the
+.URL "classical troff documentation" \
+http://\:cm.bell-labs.com/\:cm/\:cs/\:cstr/\:54.ps.gz .
+.
+.
+.\" --------------------------------------------------------------------
+.\" Emacs variables
+.\" --------------------------------------------------------------------
+.
+.\" Local Variables:
+.\" mode: nroff
+.\" End:
diff --git a/src/libs/libgroff/htmlhint.cc b/src/libs/libgroff/htmlhint.cc
new file mode 100644
index 00000000..8cb896e7
--- /dev/null
+++ b/src/libs/libgroff/htmlhint.cc
@@ -0,0 +1,98 @@
+/* Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+     Written by Gaius Mulley (gaius@glam.ac.uk)
+
+This file is part of groff.
+
+groff is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+groff is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License along
+with groff; see the file COPYING.  If not, write to the Free Software
+Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+#include "lib.h"
+
+#include <stddef.h>
+#include <stdlib.h>
+
+#include "nonposix.h"
+#include "stringclass.h"
+#include "html-strings.h"
+
+/*
+ *  This file contains a very simple set of routines shared by
+ *  tbl, pic, eqn which help the html device driver to make
+ *  sensible formatting choices.  Currently it simply indicates
+ *  to pre-html when an image is about to be created this is then
+ *  passes to pre-html.
+ *  Pre-html runs troff twice, once with -Thtml and once with -Tps.
+ *  troff -Thtml device driver emits a <src='image'.png> tag
+ *  and the postscript device driver works out the min/max limits
+ *  of the graphic region.  These region limits are read by pre-html
+ *  and an image is generated via troff -Tps -> gs -> png
+ */
+
+static int is_in_graphic_start = 0;
+static int is_inline_image = 0;
+
+/*
+ *  html_begin_suppress - emit a start of image tag which will be seen
+ *                        by pre-html.
+ */
+void html_begin_suppress(int is_inline)
+{
+  if (is_inline)
+    put_string(HTML_IMAGE_INLINE_BEGIN, stdout);
+  else {
+    put_string(HTML_IMAGE_CENTERED, stdout);
+    put_string("\n", stdout);
+  }
+}
+
+/*
+ *  html_end_suppress - emit an end of image tag which will be seen
+ *                      by pre-html.
+ */
+void html_end_suppress(int is_inline)
+{
+  if (is_inline)
+    put_string(HTML_IMAGE_INLINE_END, stdout);
+  else {
+    put_string(HTML_IMAGE_END, stdout);
+    put_string("\n", stdout);
+  }
+}
+
+/*
+ *  graphic_start - The boolean, is_inline, should be:
+ *
+ *                  FALSE if this is called via EQ, TS, PS, and
+ *                  TRUE if issued via delim $$  $ x over y $ etc.
+ */
+void graphic_start(int is_inline)
+{
+  if (!is_in_graphic_start) {
+    html_begin_suppress(is_inline);
+    is_inline_image = is_inline;
+    is_in_graphic_start = 1;
+  }
+}
+
+/*
+ *  graphic_end - tell troff that the image region is ending.
+ */
+
+void graphic_end()
+{
+  if (is_in_graphic_start) {
+    html_end_suppress(is_inline_image);
+    is_in_graphic_start = 0;
+  }
+}
diff --git a/src/preproc/html/pushback.cc b/src/preproc/html/pushback.cc
new file mode 100644
index 00000000..143392fa
--- /dev/null
+++ b/src/preproc/html/pushback.cc
@@ -0,0 +1,332 @@
+// -*- C++ -*-
+/* Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+     Written by Gaius Mulley (gaius@glam.ac.uk).
+
+This file is part of groff.
+
+groff is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+groff is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License along
+with groff; see the file COPYING.  If not, write to the Free Software
+Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+#include "lib.h"
+
+#include <signal.h>
+#include <ctype.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <errno.h>
+#include "errarg.h"
+#include "error.h"
+#include "stringclass.h"
+#include "posix.h"
+
+#include <errno.h>
+#include <sys/types.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#include "pushback.h"
+#include "pre-html.h"
+
+#if !defined(TRUE)
+#   define TRUE  (1==1)
+#endif
+
+#if !defined(FALSE)
+#   define FALSE (1==0)
+#endif
+
+#   define ERROR(X)   (void)(fprintf(stderr, "%s:%d error %s\n", __FILE__, __LINE__, X) && \
+                            (fflush(stderr)) && localexit(1))
+
+
+#define MAXPUSHBACKSTACK 4096                  /* maximum number of character that can be pushed back */
+
+
+/*
+ *  constructor for pushBackBuffer
+ */
+
+pushBackBuffer::pushBackBuffer (char *filename)
+{
+  charStack = (char *)malloc(MAXPUSHBACKSTACK);
+  if (charStack == 0) {
+    sys_fatal("malloc");
+  }
+  stackPtr = 0;   /* index to push back stack        */
+  debug    = 0;
+  verbose  = 0;
+  eofFound = FALSE;
+  lineNo   = 1;
+  if (strcmp(filename, "") != 0) {
+    stdIn = dup(0);
+    close(0);
+    if (open(filename, O_RDONLY) != 0) {
+      sys_fatal("when trying to open file");
+    } else {
+      fileName = filename;
+    }
+  }
+}
+
+pushBackBuffer::~pushBackBuffer ()
+{
+  int old;
+
+  if (charStack != 0) {
+    free(charStack);
+  }
+  close(0);
+  /* restore stdin in file descriptor 0 */
+  old = dup(stdIn);
+  close(stdIn);
+}
+
+/*
+ *  localexit - wraps exit with a return code to aid the ERROR macro.
+ */
+
+int localexit (int i)
+{
+  exit(i);
+  return( 1 );
+}
+
+/*
+ *  getPB - returns a character, possibly a pushed back character.
+ */
+
+char pushBackBuffer::getPB (void)
+{
+  if (stackPtr>0) {
+    stackPtr--;
+    return( charStack[stackPtr] );
+  } else {
+    char ch;
+
+    if (read(0, &ch, 1) == 1) {
+      if (verbose) {
+	printf("%c", ch);
+      }
+      if (ch == '\n') {
+	lineNo++;
+      }
+      return( ch );
+    } else {
+      eofFound = TRUE;
+      return( eof );
+    }
+  }
+}
+
+/*
+ *  putPB - pushes a character onto the push back stack.
+ *          The same character is returned.
+ */
+
+char pushBackBuffer::putPB (char ch)
+{
+  if (stackPtr<MAXPUSHBACKSTACK) {
+    charStack[stackPtr] = ch ;
+    stackPtr++;
+  } else {
+    ERROR("max push back stack exceeded, increase MAXPUSHBACKSTACK constant");
+  }
+  return( ch );
+}
+
+/*
+ *  isWhite - returns TRUE if a white character is found. This character is NOT consumed.
+ */
+
+static int isWhite (char ch)
+{
+  return( (ch==' ') || (ch == '\t') || (ch == '\n') );
+}
+
+/*
+ *  skipToNewline - skips characters until a newline is seen.
+ */
+
+void pushBackBuffer::skipToNewline (void)
+{
+  char ch;
+
+  while ((putPB(getPB()) != '\n') && (! eofFound)) {
+    ch = getPB();
+  }
+}
+
+/*
+ *  skipUntilToken - skips until a token is seen
+ */
+
+void pushBackBuffer::skipUntilToken (void)
+{
+  char ch;
+
+  while ((isWhite(putPB(getPB())) || (putPB(getPB()) == '#')) && (! eofFound)) {
+    ch = getPB();
+    if (ch == '#') {
+      skipToNewline();
+    }
+  }
+}
+
+/*
+ *  isString - returns TRUE if the string, s, matches the pushed back string.
+ *             if TRUE is returned then this string is consumed, otherwise it is
+ *             left alone.
+ */
+
+int pushBackBuffer::isString (char *s)
+{
+  int length=strlen(s);
+  int i=0;
+
+  while ((i<length) && (putPB(getPB())==s[i])) {
+    if (getPB() != s[i]) {
+      ERROR("assert failed");
+    }
+    i++;
+  }
+  if (i==length) {
+    return( TRUE );
+  } else {
+    i--;
+    while (i>=0) {
+      if (putPB(s[i]) != s[i]) {
+	ERROR("assert failed");
+      }
+      i--;
+    }
+  }
+  return( FALSE );
+}
+
+/*
+ *  isDigit - returns TRUE if the character, ch, is a digit.
+ */
+
+static int isDigit (char ch)
+{
+  return( ((ch>='0') && (ch<='9')) );
+}
+
+/*
+ *  isHexDigit - returns TRUE if the character, ch, is a hex digit.
+ */
+
+#if 0
+static int isHexDigit (char ch)
+{
+  return( (isDigit(ch)) || ((ch>='a') && (ch<='f')) );
+}
+#endif
+
+/*
+ *  readInt - returns an integer from the input stream.
+ */
+
+int pushBackBuffer::readInt (void)
+{
+  int  c =0;
+  int  i =0;
+  int  s =1;
+  char ch=getPB();
+
+  while (isWhite(ch)) {
+    ch=getPB();
+  }
+  // now read integer
+
+  if (ch == '-') {
+    s = -1;
+    ch = getPB();
+  }
+  while (isDigit(ch)) {
+    i *= 10;
+    if ((ch>='0') && (ch<='9')) {
+      i += (int)(ch-'0');
+    }
+    ch = getPB();
+    c++;
+  }
+  if (ch != putPB(ch)) {
+    ERROR("assert failed");
+  }
+  return( i*s );
+}
+
+/*
+ *  convertToFloat - converts integers, a and b into a.b
+ */
+
+static float convertToFloat (int a, int b)
+{
+  int c=10;
+  float f;
+
+  while (b>c) {
+    c *= 10;
+  }
+  f = ((float)a) + (((float)b)/((float)c));
+  return( f );
+}
+
+/*
+ *  readNumber - returns a float representing the word just read.
+ */
+
+float pushBackBuffer::readNumber (void)
+{
+  int i;
+  char ch;
+
+  i = readInt();
+  if ((ch = getPB()) == '.') {
+    return convertToFloat(i, readInt());
+  }
+  putPB(ch);
+  return (float)i;
+}
+
+/*
+ *  readString - reads a string terminated by white space
+ *               and returns a malloced area of memory containing
+ *               a copy of the characters.
+ */
+
+char *pushBackBuffer::readString (void)
+{
+  char  buffer[MAXPUSHBACKSTACK];
+  char *string = 0;
+  int   i=0;
+  char ch=getPB();
+
+  while (isWhite(ch)) {
+    ch=getPB();
+  }
+  while ((i < MAXPUSHBACKSTACK) && (! isWhite(ch)) && (! eofFound)) {
+    buffer[i] = ch;
+    i++;
+    ch = getPB();
+  }
+  if (i < MAXPUSHBACKSTACK) {
+    buffer[i] = (char)0;
+    string = (char *)malloc(strlen(buffer)+1);
+    strcpy(string, buffer);
+  }
+  return( string );
+}
diff --git a/src/preproc/html/pushback.h b/src/preproc/html/pushback.h
new file mode 100644
index 00000000..93cb3f1a
--- /dev/null
+++ b/src/preproc/html/pushback.h
@@ -0,0 +1,54 @@
+// -*- C -*-
+/* Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+     Written by Gaius Mulley (gaius@glam.ac.uk).
+
+This file is part of groff.
+
+groff is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+groff is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License along
+with groff; see the file COPYING.  If not, write to the Free Software
+Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+
+#define eof              (char)-1
+
+
+/*
+ *  defines the class and methods implemented within pushbackbuffer.cc
+ */
+
+class pushBackBuffer
+{
+ private:
+  char       *charStack;
+  int         stackPtr;   /* index to push back stack        */
+  int         debug;
+  int         verbose;
+  int         eofFound;
+  char       *fileName;
+  int         lineNo;
+  int         stdIn;
+
+ public:
+        pushBackBuffer (char *);
+  ~     pushBackBuffer ();
+  char  getPB          (void);
+  char  putPB          (char ch);
+  void  skipUntilToken (void);
+  void  skipToNewline  (void);
+  float readNumber     (void);
+  int   readInt        (void);
+  char *readString     (void);
+  int   isString       (char *string);
+};
+
+