Identification

The first thing a class or package file does is identify itself. Package files do this as follows:

   \NeedsTeXFormat{LaTeX2e}
   \ProvidesPackage{<package>}[<date> <other information>]

For example:

   \NeedsTeXFormat{LaTeX2e}
   \ProvidesPackage{latexsym}[1994/06/01 Standard LaTeX package]

Class files do this as follows:

   \NeedsTeXFormat{LaTeX2e}
   \ProvidesClass{<class-name>}[<date> <other information>]

For example:

   \NeedsTeXFormat{LaTeX2e}
   \ProvidesClass{article}[1994/06/01 Standard LaTeX class]

The <date> should be given in the form `YYYY/MM/DD' and must be present if the optional argument is used (this is also true for the \NeedsTeXFormat command). Any derivation from this syntax will result in low-level TEX errors--the commands expect a valid syntax to speed up the daily usage of the package or class and make no provision for the case that the developer made a mistake!

This date is checked whenever a user specifies a date in their \documentclass or \usepackage command. For example, if you wrote:

   \documentclass{article}[1995/12/23]

then users at a different location would get a warning that their copy of article was out of date. The description of a class is displayed when the class is used. The description of a package is put into the log file. These descriptions are also displayed by the \listfiles command. The phrase Standard LaTeX must not be used in the identification banner of any file other than those in the standard L^ATEX distribution.