Overview

PS-LAEMTEMEXEEMX is a modified version of LAEMTEMEXEEMX. Rather than use the Computer Modern family of fonts (CM) developed by Donald Knuth, PS-LAEMTEMEXEEMX tries to use PostScript¹ fonts wherever possible. This has a number of advantages:

There are a large number of fonts available for PostScript devices. Format designers can choose fonts more appropriate to their documents, rather than being restricted to the CM set.
Sending a document to a PostScript device can be much faster, as large character bitmaps need not be sent. Also, the disk space required by the bitmap fonts can be saved.
PostScript fonts can be arbitrarily scaled and rotated by the PostScript device.

However, there are also drawbacks:

At present there are no PostScript fonts that can entirely take the place of the CMEX, CMSY and CMMI fonts, and also the LAEMTEMEXEEMX circle, line and symbol fonts, without some loss of compatibility with LAEMTEMEXEEMX.² Therefore, these fonts are still required.
The scalability of the PostScript fonts implies that they are not as good at all point sizes as fonts specially designed to a size.
The CM and PostScript encodings of character positions are quite different; this means that substantial modification is required to LAEMTEMEXEEMX, and that any files that depend on specific character encodings (using \char or \mathchar, for instance) may not work properly with PS-LAEMTEMEXEEMX– the AMS-LAEMTEMEXEEMX package is a case in point.
The device driver that converts from TEX³ DVI format to PostScript must be capable of coping with device-resident fonts.
Some of the information required by TEX (such as that for positioning of accents) is unavailable in the PostScript fonts, or only available in different forms, which means that output may not be of optimal quality.
Documents produced with PS-LAEMTEMEXEEMX cannot be previewed using simple DVI previewers, but will require a PostScript previewer.

Having enumerated all the drawbacks, it's worth saying that most of them are not likely to affect the casual user of PS-LAEMTEMEXEEMX (except perhaps the last – and even that shouldn't be a problem as there's a free PostScript previewer called GHOSTSCRIPT available from the Free Software Foundation). However, sophisticated users should bear in mind the limitations. A detailed list of extensions and restrictions to LAEMTEMEXEEMX can be found in Sections $[*]$ and $[*]$ .

In use, PS-LAEMTEMEXEEMX should behave just as LAEMTEMEXEEMX does (except for the restrictions documented below). No modifications should be required to LAEMTEMEXEEMX documents; PS-LAEMTEMEXEEMX is not a style or style option; it replaces the standard LAEMTEMEXEEMX ``format'' file (lplain.fmt or latex.fmt) with another, called pslatex.fmt. This can be invoked explicitly by VIRTEX, so:

     $ virtex
     This is TeX, C Version 3.14t3 (no format preloaded)
     **&pslatex \input file
     (file.tex
     PostScript-based LaTeX (Times/Helvetica/Courier), Version 1.2 (NFSS)
     ...

Alternatively, your LAEMTEMEXEEMX system administrator may choose to make a ``preloaded'' version of PS-LAEMTEMEXEEMX, perhaps called pslatex. This can be used in the same way as LAEMTEMEXEEMX:

     $ pslatex file
     This is TeX, C Version 3.14t3 (format=pslatex 92.4.10)
     (file.tex
     PostScript-based LaTeX (Times/Helvetica/Courier), Version 1.2 (NFSS)
     ...

Installation instructions can be found in Section $[*]$ .