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#ident	"@(#)README	1.4	05/06/08 SMI"

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The troff in this directory
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:
	troff -Taps ...
produces output for the Autologic APS-5.
(This is the default.)

To make this work, you need two things.
First, you need to create a set of
device and font descriptions in the directory
	/usr/doctools/font/devxxx
where "xxx" is your device name.
Currently supported device is
	aps	Autologic APS-5 phototypesetter
Source for this device is found in the subdirectory
devaps of this directory.

The file "DESC" contains information about the
device itself and the character set.  (See devaps/DESC.)

In addition, each font needs a file describing its
characters, width and device-driving codes;
see R and S for typical examples.

The program "makedev" will convert these text
descriptions into a binary form that the troff can
slurp up in a single gulp during initialization;
these wind up in 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 troff
output into specific codes for your favorite typesetter.
daps.c is the driver for the APS-5;
it will serve as a useful prototype.  In particular,
it contains a precise description of the output language.
	ta	prints ascii on ordinary terminals (crudely)

One can always simply run
	troff
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.)

The recommended way to create the necessary files to make troff
able to communicate with a new output device
is to pick the most similar device for which this software
already exists, and modify it to suit the new device.

This release contains prototype software for one
type of device -- a phototypesetter (devaps)
The devaps subtree contains
profusely-commented programs and strategically placed README
files to help guide the experienced user in making
modifications to these files.

Two other source of information for users who wish to delve
deeply into this software are the manual pages
troff(5), which describes the output language produced by troff,
and font(5), which describes the format of the device
and font description files.

-----------------------------------------------------------------------------

Changes since the original release:

January, 1985:

Added optional 3rd argument to .fp command:
	.fp 3 xx longishname
causes font to be called xx but data is loaded
from longishname.out instead of xx.out.
The intent is to deal with the proliferation of fonts.

Turned NBLIST up to 2048 so can handle really big
diversions.  Tends to blow various systems.

December 1984:

Nroff modified to read ascii tables for various devices
instead of the compiled C code nonsense.  Only a few
tables converted;  details of language still subject to
change.

September 1984:

Added Molly Wagner's code to prevent side effects
during scanning of false branch of an if.

Added test warning when one removes a macro during 
its execution (more precisely, warning when a macro
evaluation has encountered a freed block).
[Disabled Nov 84;  it seemed to cause troubles]

NS = 128;  devname[] is bigger;  turned off the -t
argument (it could be a synonym for -T but that's
probably just as risky.)

July, 1984:

Added TYPESETTER environment variable

Added \X'...' command:  ... comes out as
	x X ...\n in proper place. (doesn't nest)

In \D comands, unrecognized command letters are passed through
untouched.  This makes it possible to define things like other
splines, filled polygons, etc.

\s(dd, \s(+dd, \s(-dd size commands.

Added .lf line filename to set current line number & filename

Added Dan Berry's fixes to handle horizontal resolution properly.

New, March 1984:

Dennis Ritchie's hashed macro and number register tables;
cached width computations, general cleanup.
Minor work on de-linting.

New comments 9/16/83

This version is the current evolution of 8th Edition troff.
The only changes of substance since the export version are

	the end of a sentence is more general; things like
	." .!'' etc are recognized and padded

	the "font too big for position n" error can no longer arise.
	makedev has a new parameter called biggestfont that
	ensures that all font positions are at least that big.
	this eliminates the "font X too big for position Y" message

	some minor bugs fixes have been made:
		doesn't look for ligatures in \nf
		doesn't put out WORDSP in -a

	troff no longer produces \^ and \| on output,
	but this hasn't been tested much since it takes
	character set changes too.

