Plan 9 from Bell Labs is a distributed operating system which originated from the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s and built on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 has been free and open-source. The final official release was in early 2015. Under Plan 9, UNIX's everything is a file metaphor is extended via a pervasive network-centric filesystem, and the cursor-addressed, terminal-based I/O at the heart of UNIX-like operating systems is replaced by a windowing system and graphical user interface without cursor addressing, although rc, the Plan 9 shell, is text-based. The name Plan 9 from Bell Labs is a reference to the Ed Wood 1957 cult science fiction Z-movie Plan 9 from Outer Space. The system continues to be used and developed by operating system researchers and hobbyists. History Plan 9 from Bell Labs was originally developed, starting in the late 1980s, by members of the Computing Science Research Center at Bell Labs, the same group that originally developed Unix and the C programming language. The Plan 9 team was initially led by Rob Pike, Ken Thompson, Dave Presotto and Phil Winterbottom, with support from Dennis Ritchie as head of the Computing Techniques Research Department. Over the years, many notable developers have contributed to the project, including Brian Kernighan, Tom Duff, Doug McIlroy, Bjarne Stroustrup and Bruce Ellis. Plan 9 replaced Unix as Bell Labs's primary platform for operating systems research. It explored several changes to the original Unix model that facilitate the use and programming of the system, notably in distributed multi-user environments. After several years of development and internal use, Bell Labs shipped the operating system to universities in 1992. Three years later, Plan 9 was made available for commercial parties by AT&T via the book publisher Harcourt Brace. With source licenses costing $350, AT&T targeted the embedded systems market rather than the computer market at large. Ritchie commented that the developers did not expect to do "much displacement" given how established other operating systems had become. By early 1996, the Plan 9 project had been "put on the back burner" by AT&T in favor of Inferno, intended to be a rival to Sun Microsystems' Java platform. In the late 1990s, Bell Labs' new owner Lucent Technologies dropped commercial support for the project and in 2000, a third release was distributed under an open-source license.