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## latex209.cfg

Whenever a LATEX document starts with `\documentstyle`, rather than with `\documentclass`, LATEX assumes that it is a LATEX 2.09 document and therefore processes it in `compatibility mode'. This does the following:

- sets the flag `\@compatibilitytrue`;
- inputs the file `latex209.def`;
- inputs the file `latex209.cfg` if it exists.

The LATEX 2.09 set-up allowed the format itself to be customised. When making the format with iniTEX, the process ended with this request:

> `Input any local modifications here.`

If your site did input any modifications at that point then the LATEX2e `compatibility mode' will not fully emulate LATEX 2.09 as installed at your site. In this case you should put all these `local modifications' into a file called `latex209.cfg` and put this file in the default input path at your site. These `local modifications', although not stored in the format, will then be loaded before any old-style document is processed. This should ensure that you can continue to process any old documents that made use of this local customisation.