Texinfo

Texinfo is a typesetting syntax used for generating documentation in both on-line and printed form with a single source file. It is implemented by a free computer program of the same name, created and made available by the GNU Project.
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A GNU documentation system that uses a single source file to produce both on-line information and printed output. You can read the on-line information, known as an "Info file", with an Info documentation-reading program. By convention, Texinfo source file names end with a ".texi" or ".texinfo" extension.
You can write and format Texinfo files into Info files within GNU Emacs, and read them using the Emacs Info reader. If you do not have Emacs, you can format Texinfo files into Info files using "makeinfo" and read them using "info". TeX is used to typeset Texinfo files for printing.
Texinfo is available from your nearest GNU archive site.
Current version: 3.1, as of 1993-03-23.
(1994-10-05)