Nroff is a primitive version of the UNIX nroff program.
It supports some nroff commands, but not all.  The following things need to be
done to it:

  - Add more commands (see below for supported/unsupported commands)
  - Add the 4-character nroff escape sequences (see below).  Device dependent.
  - Add more of the \ characters, especially the useful ones like:
    \\, \|, \0, \^, \&, \", \$n, \%, \*, \c, \f, \n, \o, \{, \}
  - Add the more useful number registers
  - Write a proper -ms package
  - Change command line options to be nroff-like
  - Write drivers for -Tdj (deskjet), -Tepson, -Tlp.  The default way to
    handle bold should be overprinting, and italics overstriking with _ .
  - Remove lots of nonstandard stuff where standard mechanisms work better
  - Support the following command flags.  Delete the current nonstandard ones:
    -o, -n, -m, -r, -T, 

Note: just adding more commands may cause command() to get so big the compiler
can no longer handle it.  Probably it should be split up into a separate
routine for each command.  Other routines also need to be cleaned up.


The following commands are supported
------------------------------------
.ad [mode]	Adjust
.af R {1,a,A,i,I,0...1}		Assign format to number reg
.bo [N]		Bold face
.bp [+/-N]	Begin page
.br		Break (page)
.bs [N]		Backspace in output
.c2 [c=']	Nobreak char
.cc [c=.]	Command character
.ce [N]		Center
.cu [N]		Continuous underline
.de name [end]	Define macro
.ds name string	Define string
.ec [c=\]	Escape char
.ef "a" "b" "c"	Even footer
.eh "a" "b" "c"	Even header
.en or ..	End macro def (should not get one here...)
.eo		Escape off
.fi		Fill
.fl		Flush NOW
.fo "a" "b" "c"	Footer
.ft {R,I,B,S,P}	Font change
.ig name	Ignore input lines
.in [+/-N]	Indenting
.ju		Justify
.ll [+/-N] .rm [+/-N]		Line length
.ls [+/-N=+1]	Line spacing
.lt N		Title length
.m1 N		Topmost margin
.m2 N		Second top margin
.m3 N		1st bottom margin
.m4 N		Bottom-most margin
.na		No adjust
.ne N		Need n lines
.nf		No fill
.nj		No justify
.nr R +/-N M	Set number reg
.of "a" "b" "c"	Odd footer
.oh "a" "b" "c"	Odd header
.pc [c=NULL]	Page number char
.pl N		Page length
.pm [t]		Print macro names and sizes
.pn N		Page number
.po N		Page offset
.rr R		Unset number reg
.so name	Source file
.sp [N=1]	Space
.ti [+/-N]	Temporary indent
.tr ab...	Translate
.ul [N]		Underline


The following commands are not supported, but should be, if possible:
--------------------------------------------------------
.bd	embolden
.ch	change trap
.el	else
.em	end macro
.fp	font position
.hy	hyphenation control
.ie	if-else
.if	if
.hc	hyphenation char
.ns	no space mode
.ps	point size
.rm	remove definition
.rn	rename
.rs	restore spacing
.ss	set space size
.ta	tab
.tl	titles
.tm	comment
.vs	vertical spacing
.wh	trap where


The  following lines show how the 4-character nroff escape sequences can be 
built up using overstriking.  Each line has 3 entries: escape name, length of 
sequence, codes to output, where \b is backspace.  These are device dependent,
and should come from the files invoked by the -T option.  The choices below are
for a printer with backspace and overstrike.
-------------------------------------------------------------------------------
\(!= 1 /\b=
\(& 0
\(** 1 *
\(*C 1 _\b-\b~
\(*D 2 _\b/_\b\\
\(*F 1 |\bO
\(*G 2 ~\b|~
\(*H 1 -\bO
\(*L 2 /\\
\(*P 2 ~\b|~\b|
\(*Q 1 |\bU
\(*S 1 ~\b_\b>
\(*U 1 Y
\(*W 2 _\b(_\b)
\(*a 1 <\ba
\(*b 1 ,\bB
\(*c 1 ,\b3
\(*d 1 S\bo
\(*e 1 -\bc
\(*f 1 /\bo
\(*g 1 ,\by
\(*h 1 -\b0
\(*i 1 ,\bi
\(*k 1 <\bK
\(*l 1 \\\b>
\(*m 1 ,\bu
\(*n 1 ,\bv
\(*o 1 o
\(*p 1 -\bn
\(*q 1 |\bu
\(*r 1 p
\(*s 1 -\bo
\(*t 1 ~\bt
\(*u 1 u
\(*w 1 u\bw
\(*x 1 /\b\\
\(*y 1 ,\bn
\(*z 1 ,\bL
\(+- 1 _\b+
\(-> 2 ->
\(0 1 " 
\(12 3 1/2
\(14 3 1/4
\(34 3 3/4
\(<- 2 <-
\(<= 1 _\b<
\(== 1 _\b=
\(>= 1 _\b>
\(^ 0
\(aa 1 '
\(ap 1 ~
\(br 1 |
\(bs 4 (:-)
\(bu 1 +\bo
\(bv 1 |
\(ca 3 (^)
\(ci 1 O
\(co 3 (c)
\(ct 1 /\bc
\(cu 1 U
\(da 1 |\bv
\(dd 1 I\b|
\(de 1 '\b`
\(dg 1 -\b!
\(di 1 -\b:
\(em 2 --
\(eq 1 =
\(es 1 /\bO
\(fm 1 '
\(ga 1 `
\(gr 1 ~\bV
\(hy 1 -
\(ib 2 (~\b_\b=
\(if 2 oo
\(ip 2 ~\b_\b=)
\(is 1 '\b,\bI
\(lb 1 _\b(
\(lc 1 ~\b[
\(lf 1 _\b[
\(lh 1 =\b<
\(lk 1 -\b(
\(lt 1 ~\b(
\(mi 1 -
\(mo 1 -\bC
\(mu 1 x
\(no 1 -
\(or 1 |
\(pd 1 3\bo
\(pl 1 +
\(pt 2 oc
\(rb 1 _\b)
\(rc 1 ~\b]
\(rf 1 _\b]
\(rg 3 (R)
\(rh 1 =\b>
\(rk 1 -\b)
\(rn 1 ~
\(rt 1 ~\b)
\(ru 1 _
\(sb 2 (_\b~
\(sc 1 j\bf
\(sl 1 /
\(sp 2 _\b~)
\(sq 2 []
\(sr 2 \\/
\(ts 1 s
\(ua 1 |\b^
\(ul 1 _
\(| 0
\(~= 1 ~\b=