Plan 9 is a new computer operating system and associated utilities. It has been built over the past several years by the Computing Sciences Research Center of Bell Laboratories, the same group that developed Unix, C, and C++. Plan 9 is a distributed system. In the most general configuration, it uses three kinds of components: terminals that sit on users' desks, file servers that store permanent data, and CPU servers that provide faster CPUs, user authentication, and network gateways. These components are connected by various kinds of networks, including Ethernet, Datakit, specially-built fiber networks, ordinary modem connections, and ISDN. In typical use, users interact with applications that run either on their terminals or on CPU servers, and the applications get their data from the file servers, but it's also small enough to run by itself on a laptop. It is highly configurable; it escapes from specific models of networked workstations and central machine service.