%  The size of A4 paper is 210mm x 297mm.
%  The following setting lets exactly 1in empty from each side of paper
%  and these dimensions are taken into account also when
%  \magnification is used.

\immediate\message{\string\hsize=159.2 mm \string\vsize=239.2 mm}

\hsize= 159.2 mm
\vsize= 239.2 mm

{\catcode64=11                          % \catcode`\@=11

\gdef\m@g{\mag\count@
  \hsize=159.2truemm \vsize=239.2truemm \dimen\footins8truein}

}