%%
%% The LaTeX Companion, 3ed
%%
%% Example 6-7-11 on page I-483 in "dcolumn --- Decimal column alignments".
%%
%% 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{207.0pt}
%StartShownPreambleCommands
\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{\cdot}{#1}}
\newcolumntype{.}{D{.}{.}{-1}}
\newcolumntype{,}{D{.}{,}{2}}
%StopShownPreambleCommands

\begin{document}
\begin{tabular}{|d{-1}|d{2}|.|,|}
   1.2    & 1.2    & 1.2     & 1.2      \\
   1.23   & 1.23   & 12.34   & 12.34    \\
   1121.2 & 1121.2 & 0.3333  & 0.3333   \\
   184    & 184    & \pm 100  & \pm 100 \\
   .4     & .4     & ok?     & no!      \\
   -0.55  & -0.55  & -0.55   & -0.55    \\
   0.0    & 0.0    & 0.0     & 0.0
\end{tabular}
\end{document}