\ProvidesClass & \ProvidesPackage ¶Synopses:
\ProvidesClass{clsname}[release-date [info-text]]
\ProvidesPackage{pkgname}[release-date [info-text]]
Identifies the class or package being defined, printing a message to the screen and the log file.
When you load a class or package, for example with
\documentclass{smcmemo} or \usepackage{test},
LaTeX inputs a file (smcmemo.cls and test.sty,
respectively). If the name of the file does not match the class or
package name declared in it then you get a warning. Thus, if you
invoke \documentclass{smcmemo}, and the file
smcmemo.cls has the statement \ProvidesClass{foo} then
you get a warning like You have requested document class
`smcmemo', but the document class provides 'foo'. This warning does
not prevent LaTeX from processing the rest of the class file
normally.
If you include the optional argument then you must include a date,
before any spaces, of the form YYYY/MM/DD. The rest of the
optional argument is free-form, although it traditionally identifies
the class. It is written to the screen during compilation and to the
log file. Thus, if your file smcmemo.cls contains the line
\ProvidesClass{smcmemo}[2008/06/01 v1.0 SMC memo class] and
your document’s first line is \documentclass{smcmemo} then
you will see Document Class: smcmemo 2008/06/01 v1.0 SMC memo
class.
The date in the optional argument allows class and package users to
ask to be warned if the version of the class or package is earlier
than release date. For instance, a user could enter
\documentclass{smcmemo}[2018/10/12] or
\usepackage{foo}[[2017/07/07]] to require a class or package
with certain features by specifying that it must be released no
earlier than the given date. Perhaps more importantly, the date
serves as documentation of the last release. (In practice, package
users rarely include a date, and class users almost never do.)