Plan 9 (operating system)

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Plan 9 is an Unix-like operating system developed by AT&T and later released under an open-source license. Although it includes many features similar to Unix, Plan 9 is different (and improved) in many ways. Initially, Plan 9 was intended to be commercially distributed, but Bell Labs did not maintain its commercial interest. Plan 9 was later released under a non-free license (but with the code available), and later under an open-source license. It is also the base of Inferno. Plan 9 runs on a multitude of architecture, including x86, SPARC and PowerPC.

At the moment, Plan 9 is not very widely used outside educational environment. However, it is a fairly capable operating system and could be more widely adopted if more applications and drivers were available for it.

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Features

Plan 9 includes a great number of features, with distinctive features from other operating systems in almost all its components. Plan 9 is built around a monolithic kernel, but with user-space file systems. The main features of the Plan 9 filesystem hierarchy include:

  • Any object can be named or addressed in the filesystem. This URI-based system replaces the traditional Unix way of "converting" everything through the /dev devices.
  • The ability to seamlessly and transparently bind directories spread on different media or even different networked computer in a single, local directory (union directories). This is especially interesting when trying to make devices available to a whole network: the server's /dev directory is simply bound to each of the clients' /dev directory.

These make it possible to build an entire distributed computing environment. It is much easier to create a completely distributed system, by simply binding the right directories and assigning the right functions.

Several improvements have appeared in other areas as well. Plan 9 does not use the X11 window system, but Rio, its own quick and ergonomic windowing system. Plan 9 includes Alef, a new programming language, and it can emulate Berkeley socket interfaces. It supports UTF-8 and the POSIX standards.

Acme is a highly regarded editor and programming environment, which was later cloned by Wily, a Unix program.

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