Plan 9 from Bell Labs
| Glenda, the Plan 9 mascot in a space suit, drawn by Renée French | |
| rio, default user interface of Plan 9 from Bell Labs | |
| Developer | Plan 9 Foundation, succeeding Bell Labs | 
|---|---|
| Written in | Dialect of ANSI C | 
| Working state | Current | 
| Source model | Open source | 
| Initial release | 1992 (universities) / 1995 (general public) | 
| Final release | Fourth Edition / January 10, 2015 | 
| Repository | 9p | 
| Marketing target | Operating systems research, networked environments, general-purpose use | 
| Available in | English | 
| Platforms | x86 / Vx32, x86-64, MIPS, DEC Alpha, SPARC, PowerPC, ARM | 
| Kernel type | Monolithic | 
| Influenced by | Research Unix, Cambridge Distributed Computing System | 
| Default user interface | rio / rc | 
| License | 2021: MIT 2014: GPL-2.0-only 2002: LPL-1.02 2000: Plan 9 OSL | 
| Succeeded by | Inferno Other derivatives and forks | 
| Official website | p9f | 
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.