%%
%% The LaTeX Companion, 3ed
%%
%% Example 2-2-12 on page I-44 in "The extended interface".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{183.0pt}

  % the book normally uses Times fonts in the examples but here we use CM:
  \renewcommand\rmdefault{cmr}

%StartShownPreambleCommands
\usepackage{titlesec}
\titleformat{\section}[runin]{\normalfont\scshape}
      {\S\,\oldstylenums{\thesection}.}{.5em}{}[.]
%StopShownPreambleCommands

\begin{document}
\section{The Title}
The heading is separated from the section text by
a dot and a space of one quad.
\end{document}