1. Unix-like
The Unix-like family is a diverse group of operating systems, with several major subcategories
including System V, BSD, and Linux. The name "Unix" is a trademark of The Open
Group which licenses it for use to any operating system that has been shown to conform to the
definitions that they have cooperatively developed. The name is commonly used to refer to the
large
set of operating systems which resemble the original Unix.
Unix systems run on a wide variety of machine architectures. They are used heavily as
server systems in business, as well as workstations in academic and engineering environments.
Free
software Unix variants, such as Linux and BSD, are increasingly popular. They are used in
the
desktop market as well, for example Ubuntu, but mostly by hobbyists.
Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on that
vendor's proprietary hardware. Others, such as Solaris, can run on both proprietary hardware
and on
commodity x86 PCs. Apple's Mac OS X, a microkernel BSD variant derived from NeXTSTEP,
Mach, and FreeBSD, has replaced Apple's earlier (non-Unix) Mac OS. Over the past several
years,
free Unix systems have supplanted proprietary ones in most instances. For instance, scientific
modeling and computer animation were once the province of SGI's IRIX. Today, they are
dominated by Linux-based or Plan 9 clusters.
The team at Bell Labs who designed and developed Unix went on to develop Plan 9 and
Inferno, which were designed for modern distributed environments. They had graphics built-
in,
unlike Unix counterparts that added it to the design later. Plan 9 did not become popular
because,
unlike many Unix distributions, it was not originally free. It has since been released under
Free
Software and Open Source Lucent Public License, and has an expanding community of
developers.
Inferno was sold to Vita Nuova and has been released under a GPL/MIT license.