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From: marcel@cs.caltech.edu (Marcel van der Goot)
Newsgroups: comp.text.tex
Subject: Re: Indexing multi-part page numbers
Summary: page number in dvi file = \count0
Keywords: \count0, page numbers, dvi files
Message-ID: <1991May3.225402.24923@nntp-server.caltech.edu>
Date: 3 May 91 22:54:02 GMT
References: <2155@seti.inria.fr>
Sender: news@nntp-server.caltech.edu
Organization: California Institute of Technology (CS Dept)
Lines: 42


Mark James (mark@motown.altair.fr) asked about page numbers:

>    This suggests that other aspects of TeX/LaTeX might also depend
>    upon sequential, numeric page numbers.  For example, how are page
>    numbers stored in .dvi files, so that programs such as dvips know
>    where to find page 137 when I give the "-p 137" option?  What
>    horrors await me as I proceed with this effort?

When TeX (and therefore LaTeX) ships out a page to the dvi file, one
of the things it stores are the values of registers \count0, ..., \count9.
If these are non-zero, their value is also displayed on your screen
as [1], [1.2], etc. Programs that work on dvi files get the page number
by assuming that \count0 contained the pagenumber. Indeed, in plain
TeX, \pageno is equal to \count0. Exactly how that number is interpreted
depends on the program; e.g., if you tell a program to find page 137 it
will probably look for the first page with \count0=137, but a program
might also just take the 137th page, regardless of the number stored
as \count0.
    However, the characters you print on the page to be interpreted by
the reader as ``page number'' do not need to correspond to the value
stored in register \count0. So, for instance, one could reserve a new
counter \mypage which holds the pagenumber that is printed, and is different
from the value in \count0. Then the dvi file will look just as if \count0
was the pagenumber. Unfortunately, although that method might solve
your problems, it probably requires changing the \output routine. That
is a lot easier in plain TeX than in LaTeX. Whether you want to do that
depends on how experienced you are with TeX/LaTeX.
    If you can just store every chapter in a separate file, the problems
with selecting a page in dvi drivers would go away, since each page
number occurs only once. But probably this method gives you bigger problems
in return, if you want to have references in one chapter to another chapter.
    Sorry, no instant solutions here; hope it helped anyway.


                                          Marcel van der Goot
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