\centerline{\bf A Review of Two Books}

\noindent{\sl PostScript Language  Tutorial and Cookbook},
Adobe Systems Inc., 1985, 244pp. Published by
Addison Wesley, price {\it\$}16.30.

\noindent{\sl PostScript Language Reference Manual},
Adobe Systems Inc., 1985, 321pp. Published by
Addison Wesley, price {\it\$}21.95.
\medskip
\centerline{\it Brief Introduction to PostScript}
\noindent PostScript (a trademark of Adobe Systems Inc.)
is a programming language intended for a wide
variety of printing devices, but its capabilities are best
supported on laser-printers or phototypesetters. It was created by Adobe
Systems Inc.\ as a page description language, to be directly interpreted
by intelligent printers. In most cases, \PS\ programs will be generated
automatically by higher level document-processing systems: a first glance at a \PS\ program
will confirm this view. However, the reward for learning the language
is a facility to create eye-catching graphical effects
with comparatively simple programs.
\medskip
\centerline{\it Tutorial and Cookbook}
\noindent This book is an excellent introduction to the philosophy and programming of
\PS. It is easy to read and presents the language in an interesting
way. The tutorial begins by introducing \PS\ as both a page description
and a full programming language. To understand \PS\ programs, it is
necessary to be familiar with ``stacks'' and the basic elements of
structured programming. Fortunately the book dedicates two chapters to these
fundamentals, explaining them well with the aid of some simple examples.
More advanced facilities in graphics and character-printing are introduced
gradually with many clear illustrations of the
output from simple programs. Examples are frequently re-used to illustrate
more advanced techniques, making it easier to see the relative advantages
from using them. Quite impressive graphics are shown as the results of elementary programs,
emphasising  the new possibilities offered by \PS.

Following the tutorial, the cookbook is a spectacular gallery of \PS\
plates. It shows the large range of effects that can be created from programs
written by a more skilled programmer. Each plate is presented
with the text of the program and explanations on the facing page.
This section should act as an inspiration for programmers-to-be and
a source of ideas for people who have learned the language.
\medskip
\centerline{\it \PS\ Language Reference Manual}
\noindent This gives a more detailed account of the ideas behind
\PS, but requires more concentration than the tutorial. It does not
attempt to give techniques for the effective programming of \PS.

The second half of the book is a dictionary of \PS\ commands,
with formal definitions of the syntax and precise function of each command. One
of the more interesting commands listed is called {\tt image}. We tried
this command with part of a monochrome television picture, downloaded from
our department's VAX. This was successfully reproduced though having the appearance of a photocopied
picture.
\medskip
\centerline{\it Conclusion}
\noindent Anyone intending to use \PS\ should have both these books.
Q.E.D.

\rightline{\sl Andrew J.~Stirling}

\bigskip
\centerline{\bf More \PS}
\medskip\noindent
The \PS\ snowball seems to be gathering momentum,
as IBM has now chosen \PS\ as its preferred
``desktop publishing'' standard. Adobe calculates
that there are no less than 23 laser printers supporting the
language. I still harbour a sneeky suspicion that
a ``page description language'' is not really
addressing the problem of documents, which, after all, have
a structure over and above that of page level. The
DDL (Document Description Language) of Imagen and Hewlett-Packard
seems conceptually more apposite, but at least we are advancing
in the right direction.

In a letter to TUGboat, Leslie Lamport makes some
interesting observations on the relationship between
\PS\ and {\tt dvi}. Fundamentally Lamport feels that
the rest of the world is going to adopt \PS\ as
the device-independent output format, and that
\TeX\ would have wider applicability if it too
generated \PS. Part of the immediate problem in doing this
lies in fonts. {\sl FTL systems inc} have already
converted the CMR fonts to \PS\ form, rather than pixel,
so the problems may not be insuperable. He also notes
the desirability of \MF\ producing \PS\ fonts,
complete with {\tt .tfm} files.

I'm a little less sanguine than Lamport about the
inevitability of \PS. I suspect we will shortly see
a generation of laser-printers which have a switch with
three positions: \PS, InterPress and DDL, depending on the
application required. If we are lucky, this will be
software selectable. Of course, one of the major reasons
that Xerox, Imagen etc.\ will not accept \PS\ lies in
Adobe's patenting of the character encoding form they
use. Other manufacturers therefore have to create their own
incompatible system in order to compete. If only
Gutenburg had managed to patent the printing press,
we could still be in the Dark Ages. I  jest not.

\rightline{\sl Malcolm W Clark}


