UDO is a lightweight markup language. The acronym stands for Universal Document Output. Much like the more recent reStructuredText, it is well-suited for writing documentation.
A corresponding free software program called udo can be used to convert a source document into other formats such as Apple-QuickView, ASCII, HTML, Texinfo, LinuxDoc-SGML, man page, Pure-C-Help, Rich Text Format, ST-Guide, LaTeX, Turbo Vision Help or Windows Help. UDO is released under the GNU General Public License.
References
UDO (markup language) Wikipedia(Text) CC BY-SA