Updated 5 February 2026
Below are notes on articles and books related to computing & programming, where possible with links to the originals.
February 2026 · plan9.pdf
The article is an overview of Plan 9, a distributed operating system developed at Bell Labs as a successor to Unix. It starts by explaining the motivation for building a new operating system:
Graphics and networking were added to UNIX well into its lifetime and remain poorly integrated and difficult to administer. More important, the early focus on having private machines made it difficult for networks of machines to serve as seamlessly as the old monolithic timesharing systems.
The article explains the three principles that Plan 9 is based on: a hierarchical file system that’s used not just for files but also other resources provided by various services; a standard protocol called 9P, used to access those resources; and a way to join the services together in a single private hierarchical namespace. After that, it presents how different parts of the system are designed, including the windowing system, the file server, networking, and user accounts.
There’s also a brief description of the concurrent programming language Alef.
One interesting detail is that Bell Labs’ Plan 9 system was heterogeneous, with MIPS, SPARC, and Intel machines. All software for Plan 9 was written in portable C or Alef, and the compilers were designed for cross-compilation, so programs could easily be built for all architectures.
From the perspective of 2026, Plan 9 seem impossibly ambitious. Its creators wanted a better way to do networking and to use graphical interfaces, so they came up with some new design principles for an operating system, built that operating system, started using it day-to-day and along the way created a new standard networking protocol, a new encoding for text, and a programming language for concurrent programming.
By contrast, everything we do today seems very incremental! It shows how much we’ve stagnated, especially in operating systems. We mostly seem to pile more layers on top of each other instead of designing better systems.
Another aspect I found interesting is how a small number of design principles can inform every aspect of a system. I should read some of the other Plan 9 papers to see more of how that plays out.