%
%   This is a 2-side format for TeX.  Simply
%
%   \input 2side
%   \gutter{5pt}
%
%   You want to have set your hsize, vsize, hoffset, and voffset
%   (and magnification) *before* inputting this file.
%
%   You can also say `\top{...}' and the `...' will be placed at
%   the top of the page, and the columns will be reduced
%   proportionally.  This is useful for the title of the document,
%   and any comments you might want to put later in the document.
%   Note that if you put this command after the first half of the
%   page has been `shipped', it will be postponed until the next
%   page.
%
\newdimen\fullsize\fullsize=\hsize
\newdimen\realvsize\realvsize=\vsize
\def\gutter#1{\global\advance\hsize by-#1 \global\divide\hsize by 2}%
\def\makefootline{\baselineskip24pt\hbox to\fullsize{\the\footline}}%
\let\lr=L \newbox\leftcolumn
\let\ntop=\relax
\output={\if L\lr
 \global\setbox\leftcolumn=\columnbox \global\let\lr=R
 \else\global\let\lr=L\doubleformat\global\fi
 \ifnum\outputpenalty>-20000\else\dosupereject\fi
 \global\let\ntop=\relax}%
\def\doubleformat{\shipout\vbox{\hbox{\box\topbox}%
   \hbox to\fullsize{\box\leftcolumn\hfil\columnbox}%
   \makefootline}%
 \global\vsize=\realvsize\ntop
 \advancepageno}%
\def\columnbox{\leftline{\pagebody}}%
\newbox\topbox
\def\top#1{\if L\lr\message{Setting...}
   {\hsize=\fullsize\global\setbox\topbox=\vbox{#1}%
   \global\vsize=\realvsize
   \global\advance\vsize by-\ht\topbox
   \global\advance\vsize by-\baselineskip}%
  \else\global\def\ntop{\top{#1}}\message{Saving...}%
  \fi}%
\def\bye{\vfill\eject\if R\lr\null\vfill\eject\fi\end}%

.
