Re: Determining pdf vs. dvi output at runtime

this is a common topic on tex lists.  your

> \newif\ifpdf
> \ifx\pdfoutput\undefined
>    \pdffalse % we are not running PDFLaTeX
> \else
>    \pdfoutput=1 % we are running PDFLaTeX
>    \pdftrue
> \fi

was wrong even before the advent of tetex 3 (and other distributions
that use pdftex as default enging).

the issue is summarised in

  http://www.tex.ac.uk/cgi-bin/texfaq2html?label=ifpdf

(though the last bit of code in that could be better...by two tokens.)

personally, i prefer just to load ifpdf.sty and let that define \ifpdf
for me.