doc tool in linux

[ares]

there are some doc tools in linux and they are very advanced and
userful.

1 texinfo
the default tool in gnu project.

2 tex latex
produce typeset copy usually , like dvi,ps,pdf

3 roff, groff
tex的竞争对手, man 就是用roff的宏包写的

4 sgml, xml, html
自定义标记

apart from that, there are a lot of tools which can tranlate one to
another of the basic several formats. for example ,
texi->ps,pdf,html,xml,dvi, pdf->ps,html,div ..... and so on