Xygen doxygen is a documentation system for C++, C, Java, Objective-C, Python, IDL and to some extent PHP, Fortran, VHDL and D. - Doxygen can help you in three ways: It can generate an on-line documentation browser (in HTML) and/or an off-line reference manual (in LaTeX or RTF) from a set of documented source files. There is also support for generating output in PostScript, hyperlinked PDF or compressed HTML. The documentation generated by doxygen is highly customizable: You can select the programming languages for which you want to generate docs (e.g., only for C++), you can specify your own macros that should be expanded during doc generation etc. - The most important reason why developers like using doxygen is that it can create cross references between different parts of their code. For example if you have two classes A and B where class B uses class A then doxygen will put links in the docs of both classes so that you can easily go from one to the other by just clicking on a link.