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\section{Introduction}
\PS\ is a versatile page description language normally used to
communicate with laser printers and other graphics output devices.  In
particular, it is the language understood by the public laser printers
on Athena, which are HP LaserJet 4Si.  \PS\ was developed by Adobe
Systems Incorporated for use as a standardized device independent page
description language.  This means that any document written in \PS\
will look exactly the same on any device capable of rendering \PS.

Many programs will generate \PS\ output to be interpreted by a
printer.  This saves you the effort of generating the \PS\ code by
yourself.  For example, \prog{enscript} will print plain text with
some other additions, such as filenames and page numbers.  For
formatting text, FrameMaker, \prog{ez}, \prog{troff}, \prog{dvips},
and others are available.  \prog{dvips} is special since it takes a
file output from another program, \TeX\ or \LaTeX, and generates \PS\
output from it.

\section{Where to find help}
You can find help on \PS\ in many places.  You can ask at the SIPB
office (room W20-557, x3-7787).  You can also read the so-called ``Red
Book,'' {\it \PS\ Language Reference Manual} (second edition) by Adobe
Systems, which is a good in-depth reference to the language.  There is
also the ``Blue Book,'' {\it \PS\ Language Tutorial and Cookbook},
also by Adobe Systems, which is a more of a beginner's guide.  There
is a locker on Athena, the \prog{postscript} locker, which has a
number of interesting \PS\ hacks in it.

\section{\PS\ files}
All \PS\ program files must begin with are the two characters
`{\tt\%!}'.  This is often pronounced ``percent bang.''  In \PS,
anything following a `{\tt\%}' character on a line is treated as a
comment, so these two characters which are the start of every \PS\
file are actually always treated as a comment.
\bye
