%%
%% The LaTeX Companion, 3ed
%%
%% Example 6-6-10 on page I-475 in "cellspace --- Ensure minimal clearance automatically".
%%
%% 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{111.0pt}

%StartShownPreambleCommands
\usepackage[column=O]{cellspace}
\usepackage{bigstrut}
%StopShownPreambleCommands

\begin{document}
\begin{tabular}[t]{c}    \hline
  Ä \\\hline xyz \\\hline $\frac{1}{2}$ \\\hline \end{tabular}
\begin{tabular}[t]{O{c}} \hline
  Ä \\\hline xyz \\\hline $\frac{1}{2}$ \\\hline \end{tabular}
\begin{tabular}[t]{c}    \hline
  Ä \bigstrut[t]           \\\hline xyz \\\hline
  $\frac{1}{2}$ \bigstrut               \\\hline \end{tabular}
\begin{tabular}[t]{O{c}}    \hline
  Ä \bigstrut[t]           \\\hline xyz \\\hline
  $\frac{1}{2}$ \bigstrut               \\\hline \end{tabular}
\end{document}