'dartmouthcollege' Episodes

The Dartmouth Time Sharing System and Time Sharing

     10/14/2021

DTSS, or The Dartmouth Time Sharing System, began at Dartmouth College in 1963. That was the same year Project MAC started at MIT, which is where we got Multics, which inspired Unix. Both contributed in their own way to the rise of the Time Sharing movement, an era in computing when people logged into computers over teletype devices and ran computing tasks - treating the large mainframes of the era like a utility.

The notion had been kicking around in 1959 but then John McCarthy at MIT started a project on an IBM 704 mainframe. And PLATO was doing something similar over at the University of Illinois, Champaign-Urbana. 1959 is also when John Kemeny and Thomas Kurtz at Dartmouth College bought Librascope General Purpose computer, then being made in partnership with the Royal Typewriter Company and Librascope - whichwould later be sold off to Lockheed Martin.

Librascope had Stan Frankel - who had worked on both the Manhattan Project and the ENIAC. And he architected the LGP-30 in 1956, which ended up at Dartmouth. At this point, the computer looked like a desk with a built-in typewriter.

Kurtz had four students that were trying to program in ALGOL 58. And they ended up writing a language called DOPE in the early 60s. But they wanted everyone on campus to have access to computing - and John McCarthy said why not try this new time sharing concept. So they went to the National Science Foundation and got funding for a new computer, which to the chagrin of the local IBM salesman, ended up being a GE-225.

This baby was transistorized. It sported 10,0000 transistors and double that number of diodes. It could do floating-point arithmetic, used a 20-bit word, and came with 186,000 magnetic cores for memory. It was so space aged that one of the developers, Arnold Spielberg, would father one of the greatest film directors of all time. Likely straight out of those diodes.

Dartmouth also picked up a front-end processor called a DATANET-30 from GE. This only had an 18-bit word size but could do 4k to 16k words and supported hooking up 128 terminals that could transfer data to and from the system at 3,000 bits a second using the Bell 103 modem. Security wasn’t a thing yet, so these things had direct memory access to the 225, which was a 235 by the time they received the computer.

They got to work in 1963, installing the equipment and writing the code. The DATANET-30 received commands from the terminals and routed them to the mainframe. They scanned for commands 110 times per second from the terminals and ran them when the return key was pressed on a terminal. If the return key was a command they queued it up to run, taking into account routine tasks the computer might be doing in the background.

Keep in mind, the actual CPU was only doing one task at a time, but it seemed like it was multi-tasking! Another aspect of democratizing computing across campus was to write a language that was more approachable than a language like Algol. And so they released BASIC in 1964, picking up where DOPE left off, and picking up a more marketable name.

Here we saw a dozen undergraduates develop a language that was as approachable as the name implies. Some of the students went to Phoenix, where the GE computers were built. And the powers at GE saw the future.

After seeing what Dartmouth had done, GE ended up packaging the DATANET-30 and GE-235 as one machine, which they marketed as the GE-265 the next year. And here we got the first commercially viable time-sharing system, which started a movement. One so successful that GE decided to get out of making computers and focus instead on selling access to time sharing systems. By 1968 they actually ended up shooting up to 40% of the market of the day.

Dartmouth picked up a GE Mark II in 1966 and got to work on DTSS version 2. Here, they added some of the concepts coming out of the Multics project that was part of Project MAC at MIT and built on previous experiences. They added pipes and communication files to promote inter-process communications - thus getting closer to the multiple user conferencing like what was being done on PLATO with Notes.

Things got more efficient and they could handle more and more concurrent sessions. This is when they went from just wanting to offer computing as a basic right on campus to opening up to schools in the area. Nearby Hanover High School started first and by 1967 they had over a dozen. Using further grants from NSF they added another dozen schools to what by then they were calling the Kiewit Network. Then added other smaller colleges and by 1971 supported a whopping 30,000 users. And by 73 supported leased line connections all the way to Ohio, Michigan, New York, and even Montreal.

The system continued on in one form or another, allowing students to code in FORTRAN, COBOL, LISP, and yes… BASIC. It became less of a thing as Personal Computers started to show up here and there. But BASIC didn’t. Every computer needed a BASIC. But people still liked to connect on the system and share information. At least, until the project was finally shut down in 1999. Turns out we didn’t need time sharing once the Internet came along.

Following the early work done by pioneers, companies like Tymshare and CompuServe were born. Tymshare came out of two of the GE team, Thomas O’Rourke and David Schmidt. They ran on SDS hardware and by 1970 had over 100 people, focused on time sharing with their Tymnet system and spreading into Europe by the mid-70s, selling time on their systems until the cost of personal computing caught up and they were acquired by McDonnell Douglas in 1984.

CompuServe began on a PDP-10 and began similarly but by the time they were acquired by H&R Block had successfully pivoted into a dial-up online services company and over time focused on selling access to the Internet. And they survived through to an era when they migrated their own proprietary tooling to HTML in the late 90s - although they were eventually merged into AOL and are now a part of Verizon media. So the pivot bought them an extra decade or so.

Time sharing and BASIC proliferated across the country and then the world from Dartmouth. Much of this - and a lot of personal stories from the people involved can be found in Dr Joy Rankin’s “A People’s History of Computing in the United States.” Published in 2018, it’s a fantastic read that digs in deep on the ways that many of these systems evolved. There are other works, but she does a phenomenal job tying events into one another.

One consistent point across her book is around societal impact. These pioneers democratized access to computing. Many of those who built businesses around time sharing missed the rapidly falling price of chips and the ready access to personal computers that were coming. They also missed that BASIC would be monetized by companies like Microsoft. But they brought computing to high schools in the area, established blueprints for teaching that are used through to this day, and as Grace Hopper did a generation before - made us think of even more ways to make programming more accessible to a new generation with BASIC.

One other author of note here is John Kemeny. His book “Man and the computer” is a must read. He didn’t have the knowledge of the upcoming personal computing - but far more prophetic than not around cloud operations as we get back to a time sharing-esque model of computing. And we do owe him, Kurtz, and everyone else involved a huge debt for their work. Many others pushed the boundaries of what was possible with computers. They pushed the boundaries of what was possible with accessibility. And now we have ubiquity.

So when we see something complicated. Something that doesn’t seem all that approachable. Maybe we should just wonder if - by some stretch - we can make it a bit more BASIC. Like they did.


(OldComputerPods) ©Sean Haas, 2020