Brian Kernighan on the origins of Unix

He began by introducing Bell Labs, which was formed by US telecommunications giant AT&T to carry out research on how to improve telephone services. A lot of inventions came out of Bell Labs, including the transistor, the laser, and fiber optics. Such was the concentration of talent there that, at one point, Claude Shannon and Richard Hamming shared an office. Kernighan joined Bell Labs in 1967, when there were about 25 people engaged in computer-science research.

Early on, Bell Labs joined up with MIT and General Electric to work on a time-sharing operating system known as Multics. As one might have predicted, the attempted collaboration between a research lab, a university, and a profit-making company did not work all that well; Multics slipped later and later, and Bell Labs eventually pulled out of the project. That left two researchers who had been working on Multics — Ken Thompson and Dennis Ritchie — without a project to work on.

After searching for a machine to work on, Thompson eventually found an old PDP-7, which was already obsolete at that time, to do some work on filesystem design. The first Unix-like system was, in essence, a test harness to measure filesystem throughput. But he and Ritchie later concluded that it was something close to the sort of timesharing system they had been trying to build before. This system helped them to convince the lab to buy them a PDP-11/20 for further development. The initial plan was to create a system for document processing, with an initial focus of, inevitably, preparing patent applications. The result was "recognizably Unix" and was used to get real work done.

The first Unix versions were entirely done in assembly, but the Multics project had shown that higher-level languages could be used for operating-system development. Starting with the BCPL language used there, Thompson pared it down to a language called B; Ritchie then added niceties like a type system, creating C. The C language hit a "sweet spot" in language design that has proved hard for anybody else to hit since, Kernighan said.

The advent of C brought the development of a wide range of system tools, perhaps the most important of which was Steve Johnson's portable C compiler, which made the operating system itself portable. Around this time pipes were added as well. That was the genesis of one of the core Unix ideas: write small tools that can be combined to solve complicated problems.

Sixth-edition Unix, released in 1975, was the first widely used version of the operating system. It included a number of other core Unix concepts, including the hierarchical filesystem, devices represented as files, a programmable shell, regular expressions, and more. All of this was implemented in about 9,000 lines of C code. The system was small and comprehensible, which led to a lot of interesting things, including the highly influential Lions' Commentary on Unix.

The 1980s were the golden age of Unix, Kernighan said. Unix was everywhere and widely respected. Thompson and Ritchie were given the Turing Award for their work. The absolute peak, he said, was when Unix appeared in the film Jurassic Park. But then the fight between AT&T and Berkeley began, leading to a pointless lawsuit, and the beginning of the fragmentation of the system.

In 1991, Linus Torvalds announced his work on Linux, and "the rest is history".

Kernighan moved into his conclusion by asking what the technical legacy of Unix is. Some significant pieces of that legacy, including the hierarchical filesystem, use of high-level languages, and the programmable shell, have their origins in Multics. Others, including pipes, the whole tools concept, and regular expressions, are a direct result of the Unix work. And most importantly, he said, was that Unix brought a new philosophy on how to create software.

Almost all of this was in place by 1975 and, he said, it may well be true that there have been no great insights into operating-system design since. Certainly Unix has seen a lot of additions, including networking, multiprocessor support, graphical interfaces, Unicode, and more. But it's all built on the foundation created nearly 50 years ago.

The creation of Unix was the result of an accidental combination of factors, starting with the juxtaposition of two exceptionally creative people "with good taste". Kernighan gave a lot of credit to "benign management" at Bell Labs that allowed this work to go forward, naming Doug McIlroy in particular. It was also spurred by the arrival of cheap hardware (in which category he included the $50,000 PDP-11 used to develop the system early on). But a key part was the Bell Labs working environment, which included stable funding and a long-term view, which is something that is hard to find today.

Could something like Unix happen again? There are plenty of talented people around now, he said, and good management does exist. Hardware has never been cheaper, and most of the software is free. But, he said, good environments for the creation of this kind of work are hard to find. Even so, he concluded, think of all the great things that began with one or two people and a good idea; that can certainly happen again. Ritchie once said that Unix was created to provide a community where interesting things could happen; we should try to create such a community again.

In your editor's opinion, Kernighan missed an opportunity to evaluate the free-software community in these terms. Companies may not have long time horizons, but many free-software projects do. It is, still, a place where people with good ideas can come together and see where those ideas lead. It would have been good to hear his thoughts on whether the free-software community has become that place where interesting things can happen and, if not, what we should seek to change to get there.

[The video of this talk is available on YouTube.]