\newwrite\indexfile
\def\makeindex{%
\immediate\openout\indexfile=\jobname.idx%
\def\index{\wrindex\indexfile}}
\def\wrindex#1#2{\xdef\gtempa{\write#1{%
#2<tab>\number\count0}}\gtempa}
\def\index{\begingroup \xindex}
\def\xindex#1{\endgroup}
\makeindex