% Copyright 2007 TeX Users Group.
% You may freely use, modify and/or distribute this file.

\documentclass{article}

% The file dumptfm.tex

\pretolerance=10000
% \raggedright

\usepackage[T1]{fontenc}
\usepackage[T1]{em}

\begin{document}

\rm

% To keep the listing short, his does not show zero-width characters

\noindent
\bgroup
\newcount\n
\n=0
\loop\ifnum\n<255
\setbox0=\hbox{\char\n}%
\ifdim0pt=\wd0\else
\the\n~\the\wd0~\box0\ \fi
\advance\n by1\repeat
\egroup

% Ignore the missing character messages

\end{document}