Non-fiction: Plan 9 from Bell Labs (operating system)

Overview
Plan 9 from Bell Labs is an operating system developed by researchers at Bell Labs, including Ken Thompson and Rob Pike, that rethinks Unix principles for a distributed computing world. First circulated in the early 1990s, it treats computation as a network of cooperating, small programs and presents a unified, file-oriented view of system resources. The design emphasizes simplicity, uniformity, and the idea that networked resources should be as easy to use as local files.

Core Design Principles
Plan 9 extends the Unix maxim "everything is a file" by applying it uniformly across devices, network connections, and graphical interfaces. Rather than building heavyweight kernel services, the system pushes functionality into a collection of modest, specialized servers and tools that communicate through a simple file protocol. This separation keeps the kernel minimal and puts state and policy in user-level processes where they are easier to reason about and modify.

Namespace and File Interface
A central innovation is the per-process namespace: each process can construct its own view of the file hierarchy by mounting and binding resources, so different programs can see different arrangements of the same underlying services. The 9P protocol (a compact file-service protocol) defines how clients interact with file servers over local or network connections. Because 9P exposes resources as files, accessing a remote printer, memory device, or window is syntactically identical to reading or writing a local file, making distributed computation feel like local I/O.

System Architecture and Components
The architecture consists of a small kernel that multiplexes hardware and a set of user-level servers that export resources via 9P. Dedicated servers handle storage, authentication, name resolution, and device access, while clients mount these servers into their namespaces. The window system and utilities are implemented as file-accessible services, and many traditional kernel responsibilities, such as device drivers and filesystem logic, run in user space. This modular layout simplifies development and debugging and encourages recomposition of services.

Programming and Interaction
Plan 9 promotes a lightweight programming culture with small, composable tools and a focus on textual, file-based interfaces. The system includes its own shell and tools optimized for the new namespace semantics, and introduces mechanisms like the plumber to route and transform messages between programs. Languages used in development ranged from C to experimental languages such as Alef, and the environment supports building complex applications by composing simple programs that share resources via the file protocol.

Impact and Legacy
Plan 9 influenced subsequent research and systems by demonstrating how a compact, file-oriented protocol and per-process namespaces simplify distributed systems design. The 9P protocol and many Plan 9 ideas found their way into later projects, including Inferno and various research systems, and concepts such as UTF-8 encoding were refined by the team and later gained wide adoption. Although Plan 9 did not replace Unix in mainstream computing, its architectural lessons continue to inform modern distributed systems, containerization concepts, and lightweight service-oriented designs.