[ excerpt from developer's web site ]

Texinfo is the official documentation format of the GNU project.
It was invented by Richard Stallman and Bob Chassell many years
ago, loosely based on Brian Reid's Scribe and other formatting
languages of the time. It is used by many non-GNU projects as well.

Texinfo uses a single source file to produce output in a number of
formats, both online and printed (dvi, html, info, pdf, xml, etc.).
This means that instead of writing different documents for online
information and another for a printed manual, you need write only
one document. And when the work is revised, you need revise only
that one document. The Texinfo system is well-integrated with GNU
Emacs.

WWW: http://www.gnu.org/software/texinfo/
