# [Tugindia] what are .cls files?

Manoj Kummini kummini at math.ukans.edu
Thu Nov 27 20:45:36 CET 2003

```On Thu, Nov 27, 2003 at 22:03:12hrs +0530, Jagadeesh Bhaskar wrote:

> i have a lot of .cls files that i know are related to Latex........what is
> its use?

These files (called class files) contain information about converting
logical structure and markup to physical type-setting. E.g., the standard
article.cls contains commands that define the options `a4paper', `12pt',
`draft' etc. In addition, it defines commands like `\maketitle',
`\section', describing how these should be typeset (spaces, numbering, font
size, shape etc.). Class files are loaded with the \documentclass macro,
and a LaTeX file can be of only one class. In addition to the standard
classes, (article, letter, book, report), most publishing houses have their
class files, which format the document in a way acceptable to them. Some of
them are amsart and amsbook from AMS, IEEEtran from IEEE, elsart from
Elsevier etc.

> when i tried to include ".cls" file names in \usepackage{} as using ".sty"
> files,it gave error saying that ".sty" file is missing!!

A \usepackage{} instructs LaTeX2e to look for a file with .sty extension.

Files with .sty extension, called packages, contain information that can be
used with many classes. E.g., the package amsmath.sty provides
mathematical symbols, and can be used with any class. These files contain
general information, and not many things that are specific to the actual
formatting of the text.

If you use a distribution on a Unix and/or GNU/Linux system, you will find
a file called clsguide.dvi, which gives philosophical and practical raison
d'etre of classes and packages. You can access it by `texdoc clsguide' from
prompt. If you don't have it on your distribution, you can get it from
CTAN.

With regards,
Manoj.

--
Manoj Kummini
Graduate Student, Dept. of Mathematics, The Univ. of Kansas,
Lawrence KS 66045 USA.  38 deg 55 min N, 95 deg 14 min W.
http://www.math.ukans.edu/~kummini/index.html
```