A documentation generator is a programming tool that generates documentation intended for programmers (API documentation) or end users (End-user Guide), or both, from a set of specially commented source code files, and in some cases, binary files.
Document generation can be divided in several type of documents:
You can place every type of document you come across in one of these categories. A lot of software solutions are offered on the Internet that can automate these processes. In particular, some integrated development environments provide interactive access to documentation, code metadata, etc.