Doxygen is the de facto standard tool for generating documentation from annotated C++ code. It is a powerful tool that can produce a wide range of documentation formats, including HTML, PDF, and XML. Doxygen is free to download and use on Windows, Mac, and Linux.
Doxygen supports a wide range of annotation commands that allow you to document your code in great detail. You can use these commands to document functions, classes, variables, and other code elements. Doxygen will then use this information to generate detailed documentation that is easy to read and understand.