Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!gatech!udel!princeton!silence!jay
From: jay@silence.princeton.nj.us (Jay Plett)
Newsgroups: comp.text
Subject: Re: International (8 bit clean) troff proposal
Summary: independence is a relative thing
Message-ID: <679@silence.princeton.nj.us>
Date: 2 Jan 91 23:18:12 GMT
References: <1990Dec27.155046.14520@cbnewsl.att.com> <1991Jan2.024946.10442@blilly.UUCP>
Organization: home
Lines: 28

In article <1991Jan2.024946.10442@blilly.UUCP>, bruce@balilly.UUCP (Bruce Lilly) writes:
 ...
> The 'd' and 'i' in ditroff atnd for "device" and "independent",
> respectively.  Ditroff output is *not* tailored to any particular device.
> The ditroff output can be interpreted by postprocessors for specific
> devices. ...
That's misleading.  Ditroff output is not only device dependent, it
is dependent on a particular set of width tables for a particular
device.  Ditroff and the postprocessor MUST use the same set of
width tables.  Ditroff outputs motions that are derived from the
width tables.  Moreover, when a character does not exist in the
current font, no font change is encoded in ditroff's output.
Ditroff assumes that the postprocessor will not only have the same
widths, but that it will also use the same strategy for noticing
that a font change is necessary and for finding the same character
in the same font that ditroff found it in.

The "di" in ditroff means that device dependence is bound at
run-time rather at compile-time.

> Postprocessor output *is* tailored to a specific device, hence is not
> suitable for widespread distibution.
If the same device will be used, there's no harm in distributing
postprocessor output.  It would be rash to distribute ditroff output
and expect it to print correctly, quite possibly even among similar
systems at the same site.

	...jay