\documentclass{article}

\usepackage[english,french,austrian,german]{babel}
%\usepackage{babel}

\usepackage{makeidx}

\makeindex
\title{Babel}
\author{XYZ}

%\newcommand{\DQ}[1]{\dq#1~~"#1}

\begin{document}
The initial language is : 
\iflanguage{german}{german}{bonga}
\\
\today\\
\newcommand{\DQ}[1]{\dq#1~~\"#1}

\maketitle

\selectlanguage{french}
\'a\'e\'i\'b\'o\'u\\
\`a\`e\`i\`b\`o\`u\\
\^a\^e\^i\^b\^o\^u\\
\'A\'E\'I\'B\'O\'U\\
\`A\`E\`I\`B\`O\`U\\
\^A\^E\^I\^B\^O\^U\\
This checks current language (?) : %\current@language
\iflanguage{french}{french}{bonga}\\
\today\\
\tableofcontents

\selectlanguage{german}
This checks current language (?) : %\current@language
\iflanguage{german}{german}{bonga}\\
\today\\
\begin{abstract}
This is the abstract.
\end{abstract}

\section{Correspondences in German}
\index{Correspondances in German}
\DQ{s}\\
\DQ{S}\\
\DQ{a}\\
\DQ{A}\\
\DQ{e}\\
\iflanguage{german}{german}{bonga}~before entering ``table''
\begin{table}
\selectlanguage{french}
\caption{NOTABLE}
\iflanguage{french}{french}{bonga}~declared for the ``table''
\end{table}
The language now is (german? french?) : \iflanguage{german}{german}{bonga}
~when you get out outside the ``table''\\
\DQ{E}\\
\DQ{i}\\
\DQ{I}\\
\DQ{o}\\
\DQ{O}\\
\DQ{u}\\
\DQ{U}

\section{Quotes}
\index{Quotes}
\noindent
Trying out the quotation mark itself : \dq\\
\glqq Trying out quotes \grqq\\
\glq Trying out single quotes \grq\\
\flqq Trying out French quotes \frqq\\
\flq Trying out french single quotes \frq\\
%\"<\\
%\">\\
%\"`\\
%\"'

\selectlanguage{english}\\
\today\\
The language is : \iflanguage{english}{english}{bonga}

\section{Correspondences in French}
\index{Correspondences in French}
\selectlanguage{french}
The language is : \iflanguage{french}{french}{bonga}\\
\today\\
\newcommand{\LS}[1]{`#1~~\`#1}
\newcommand{\RS}[1]{'#1~~\'#1}
\newcommand{\HAT}[1]{$\wedge$#1~~\^#1}

\LS{a}\\
\RS{e}\\
\HAT{u}\\

\selectlanguage{austrian}\\
\today\\
The language is : \iflanguage{austrian}{austrian}{bonga}

\appendix

\section{Bonga}
ahh .. this works as well !!

\printindex

\end{document}
