Two of the other half-dozen historical
troff macro libraries,
are still in use. BSD Unix has its own elaborate
extended macro set,
All these are designed for writing technical manuals and long-form
documentation. They are similar in style but more elaborate than man
macros, and oriented toward producing typeset output.
A minor variant of
produces output for devices that can only support constant-width
fonts, like line printers and character-cell terminals. When you view
a Unix manual page within a terminal window, it is nroff that has
rendered it for you.
The Documenter's Workbench tools do the technical-documentation
jobs they were designed for quite well, which is why they have
remained in continuous use for more than thirty years while computers
increased a thousandfold in capacity. They produce typeset text of
reasonable quality on imaging printers, and can throw a tolerable
approximation of a formatted manual page on your screen.
They fall down badly in a couple of areas, however. Their stock
selection of available fonts is limited. They don't handle images
well. It's hard to get precise control of the positioning of text or
images or diagrams within a page. Support for multilingual documents
is nonexistent. There are numerous other problems, some chronic but
minor and some absolute showstoppers for specific uses. But the most
serious problem is that because so much of the markup is presentation
level, it's difficult to make good Web pages out of unmodified
Nevertheless, at time of writing man pages remain the single
most important form of Unix documentation.