Ceci est une ancienne révision du document !
— section: The joy of TeX errors date: 2014-06-10 —
# Entering compatibility mode
You run your LaTeX job, and it starts by saying ```latex Entering LaTeX 2.09 COMPATIBILITY MODE ``` followed by lines of asterisks and `!!WARNING!!`.
This means that the document is not written in
syntax, and that there is no guarantee that all parts of the document
will be formatted correctly.
If the document is someone else's, and you want no more than a copy to read, ignore the error. The document may fail elsewhere, but as often as not it will provide a `dvi` or `pdf` that's adequate for most purposes.
If it's a new document you have just started working on, you have been misled by someone. You have written something like:
or, more generally:
These forms are (as the warning says) LaTeX 2.09 syntax, and to get rid of the warning, you must change the command.
The simple form is easy to deal with:
The complex form is more difficult, since LaTeX 2.09
conflate two sorts of things — options for the class (such as
`11pt`, `fleqn`), and packages to be loaded.
because `11pt` happens to be a class option, while [`verbatim`](https://ctan.org/pkg/verbatim) is a package.
There's no simple way to work out what are class options under LaTeX 2.09; for [`article`](https://ctan.org/pkg/article), the list includes `10pt`, `11pt`, `12pt`, `draft`, `fleqn`, `leqno`, `twocolumn` and `twoside` — anything else must be a package.
Your document may well
just work after changes like those above;
if not, you should think through what you're trying to do, and consult
documentation on how to do it — there are lots of
[free tutorials](FAQ-tutorialsstar) to help you on your way, if you
don't have access to a LaTeX manual of any sort.