The troff in this directory (known as a.out)
is a troff that produces machine-independent output.
It requires a file of descriptive information about
the particular typesetter you have in mind, and produces
output parameterized for that device.

Thus:
	a.out -T202 ...
produces output for the mergenthaler linotron 202.
(This is the default.)

To make this work, one needs to create a set of
device and font descriptions in the directory
	/usr/lib/font/devxxx
where "xxx" is your device name.
Currently supported devices are
	202	mergenthaler 202 using our software
	aps	autologic aps5
	cat	gsi cat (not really working at present)

The file "DESC" contains information about the
device itself and the character set.  The file dev202/DESC
is a good example; follow the format closely.

In addition, each font needs a description of its
characters, width and device-driving codes;
see dev202/R and S for typical examples.

The program "makedev" will convert these text
descriptions into a binary form that the a.out can
slurp up in a single gulp during initialization;
these wind up in dev202/DESC.out (which includes
default font info) and XX.out for info about font XX.

The second half of the job is to write a post-processor
that converts the more or less machine-independent a.out
output into specific codes for your favorite typesetter.
d202.c is the driver for the 202;
it will serve as a useful prototype.  In particular,
it contains a precise description of the output language.
Other postprocessors are
	daps	aps5
	dcat	graphic systems CAT (not really up to date)
	tc	tektronix 4014
	hc	hp2621 (mainly for crude graphics)
	ta	prints ascii on ordinary terminals (crudely)
	dcan	driver for Imagen/Canon laser printer
	d8400	untested driver for compugraphics 8400

The 202 driver writes onto /dev/202 in the same way that
old troff writes on /dev/cat; to get its output on the std output,
use, e.g., d202 -t ... >file.

One can always simply run
	a.out
and look at the output; it is guaranteed to be ascii text
and thus safe to edit, grep, etc.
(Since it is ascii, it is also guaranteed to be quite voluminous.)
On our system, /usr/bin/troff is actually a shell program
that detects -Txxx arguments;  the current default is 202.

Putting output codes into the font description files
seems like the right thing to do but I'm not happy yet.
Accordingly, the formats of any or all of the files
described here are subject to drastic change; hang loose.

To clear up one potential misapprehension, the code in this
directory has not been retrofitted to make an nroff. 
That would require major surgery, primarily on n6.c and n10.c.

As it says in the Unix warranty:
	"There is no warranty of merchantability nor any warranty
	of fitness for a particular purpose nor any other warranty,
	either express or implied, as to the accuracy of the
	enclosed materials or as to their suitability for any
	particular purpose.  Accordingly, Bell Telephone
	Laboratories assumes no responsibility for their use by the
	recipient.   Further, Bell Laboratories assumes no obligation
	to furnish any assistance of any kind whatsoever, or to
	furnish any additional information or documentation."

Nevertheless, I will try to answer questions in cases of
dire necessity.  Suggestions and other comments would be appreciated.

Brian W. Kernighan