From the PDP-7 to your pocket

By Drew Fustini. Posted

Last time I was in Seattle, I took a trip to the amazing Living Computers Museum to see a restored PDP-7, the iconic minicomputer from the mid-sixties that my Twitter handle pays homage to. Only five are known to have survived over the years, of which two are functional. The one I went to visit at the Living Computers Museum has been restored to do something extremely special: run UNIX Version 0.

Fifty years after Version 0, UNIX is everywhere. It is the root of the family tree that gave us macOS, Linux, and the operating system for every single iPhone and Android device. The impact UNIX has had on modern computing is impossible to overstate, and it all started with one borrowed PDP-7 at Bell Labs.

Bell Labs was the research division of AT&T, the only phone company in the USA at the time. AT&T’s monopoly meant that Bell Labs had plenty of money for research, leading to inventions including the transistor, the laser, and the photovoltaic cell. It was in this culture of innovation that a small team of computer scientists, including Ken Thompson and Dennis Ritchie, were attempting to solve the big computing problem of the day: time-sharing.

In those days, if you wanted a computer to solve a problem, you had to write instructions in assembly code, put it onto punch cards, then hand those cards to the computer operator to input when the next batch processing slot was available. Depending on how busy the machine was, this could take hours, days, or even weeks. Bell Labs was part of an ambitious project named Multics that aimed to create a time‑sharing operating system that could handle multiple users at once.

Bell Labs eventually deemed Multics a failure, which left Thompson and the rest of the team without direction or, crucially, a computer. Undeterred, they found an unused PDP-7 in another department, who were persuaded to loan it out. In 1969, Thompson’s family went on a three-week vacation while he wrote an assembler, a file editor, and a kernel for the borrowed PDP-7. By the time his family returned, Thompson had created a multi-user time-sharing operating system: UNIX Version 0.

There is so much more to this story: the creation of the C programming language, the beginning of the free software movement, and the adventures of Thompson’s pet crocodile. I’d recommend the [Command Line Heroes podcast]( "Command line heroes podcast"), or you can make the trip over to the Living Computers Museum and see it for yourself!

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