Doxygen

Doxygen is a documentation generator for software development. It processes source code to extract documentation from specially formatted comments and produces output suitable for API references and user guides. It supports many programming languages and is used to document large software projects.

Supported languages include C, C++, C#, Java, Objective-C, Python, PHP, and others. It reads documentation blocks embedded in code, using commands such as \brief, \param, \return or their at-notation equivalents. It can document classes, namespaces, files, methods, and variables, and can generate cross-references between entities. It can also generate diagrams using Graphviz, including inheritance, collaboration, and call graphs, as well as dependency graphs.

Output formats: HTML and LaTeX by default, with optional output in RTF, man pages, and XML. LaTeX can be compiled to PDF. It can produce an API reference, user manuals, and diagrams. It is configurable via a single configuration file called Doxyfile, which controls input paths, project metadata, language options, extraction rules, and diagram generation.

History and license: Doxygen was created by Dimitri van Heesch and released in the late 1990s. It is open-source software distributed under the GNU General Public License (GPL). It is widely used in open source and commercial projects to maintain up-to-date API documentation with minimal maintenance.