Doxygen is a documentation system able to generate on-line documentation from a set of documented source files. This is useful to find your way in the source distribution without having to download the source code itself. You can also visualize the relations between the various elements by means of include dependency graphs, inheritance diagrams, and collaboration diagrams, which are all generated automatically. Code_Saturne source code is only partly doxyfied. Nonetheless, automatic documentation is provided for the main sub-systems of the Code_Saturne package.