What We Know – Dennis Ritchie Thesis

What We Know, and What We Think, about the dmr thesis and Dennis the Person

In December 1967, Dennis had nearly completed his doctoral thesis, which weighed in at nearly 180 pages of dense mathematical expressions and symbols. In January 1968, he sent out two identical copies of the document to two close associates, initial faculty advisor (by then gone from Harvard for several years) Patrick Fischer, and grad school colleague Albert Meyer. This late draft still needed more than 50 simple typing corrections spread over 30 pages. On the Fischer copy title page, Dennis wrote the names of his four faculty advisors. (Image link to the right.)

dmr Fischer Copy – One of them to his original thesis advisor, Patrick Fischer
dmr Meyer Copy – One of them to his student colleague, Albert Meyer

The following month, February 1968, Dennis had produced a new, near complete draft, correcting all typos from the January draft. A small note taped to the cover page listed six minor still-to-be-made corrections. This near-final draft, its first few pages now disfigured, was found by David Brock in Dennis’ personal archives after the family donated his papers to the Computer History Museum.

On February 7, 1968, Bell Labs wrote to Harvard asking:

“Gentlemen:

“…Would you please verify for our information that Dennis M. Ritchie will receive his Doctor of Philosophy degree in Mathematics in February 1968. Thank you very much.”

To which Harvard replied on February 20th…

“With reference to your inquiry of February 7, 1968, this is to inform you that Mr. Dennis M. Ritchie is not a candidate for his Doctor of Philosophy degree in February 1968.

So by February 20, 1968, it appears that Dennis was no longer on his PhD track. There are two rumors about how the thesis came to be derailed.

The first comes from Albert Meyer who in 2018 related the story told to him by Pat Fischer…

“As Pat tells the story, Dennis had submitted his thesis. It had been approved by his thesis committee, he had a typed manuscript of the thesis that he was ready to submit when he heard that the library wanted him to have it bound, and give to them. And the binding fee was something noticeable at the time. I forget whether it was, you know, $50, $250, something or other. But it was a– not an impossible, but a non-trivial sum. And as Pat said, Dennis’ attitude was, “If the Harvard Library wants a bound copy for them to keep, they should pay for the book, because I’m not going to!” And apparently, he didn’t give on that. And as a result, never got a Ph.D. So he was more than everything but thesis. He was everything but bound copy.”

The second rumor comes from sister Lynn. In her 2018 interview with David Brock, she says…

“There was something about how he had already got the job at Bell Labs and he had gone over the three years somehow, the allocated time, by just a few months, I think. And when he came to submit it he discovered that he was going to have to pay like an extra year’s fees. And he just thought, “That’s ridiculous,” you know.

As described by Brock in his CHM article…

“Brother John feels that there was something else going on with Dennis Ritchie’s actions beyond a fit of pique about fees: He already had a coveted job as a researcher at Bell Labs, and ‘never really loved taking care of the details of living.’”

These stories basically match up, it makes sense that Dennis could have had an administrative fee-based flare-up that stopped his thesis in its tracks. Why not? This is as good an explanation as any for what might have happened.

How Did the Story Get So Thoroughly Buried?

Brother Bill has a different perspective on the story. It starts with a question… How is it that the dmr thesis so completely disappeared from public consciousness so fast and for so long? For the next fifty years, publications and award presenters didn’t know whether Dennis had a PhD or not. Interviewers couldn’t bring themselves to ask the question or raise the topic. This was happening even as Dennis was being awarded the National Medal of Technology, the Turing Award, the Japan Prize.

Here are the relevant references we could find from 1968 to 2011:

– In 1982, Electronics Magazine presented Dennis and Ken their annual Award for Achievement. The accompanying article accurately reports that “Ritchie joined the labs in 1967 after eight years in which he ‘almost’ attained a doctorate from Harvard.”

– In 1983, when Dennis and Ken won the Turing Award, the official Dennis biography on the website stated that “Ritchie received a BS degree in Physics in 1963 and a PhD in Applied Mathematics in 1967 from Harvard University.”

– In 1991, a Unix World article, “Who Is The Real Dennis Ritchie”… inaccurately states “He holds three degrees from Harvard: A Ph.D. in applied mathematics, an M.S. in applied mathematics, and a B.S. in physics.”

– Dennis and Ken won the National Medal of Technology in 1998. The “Dennis Ritchie Laureate” biography page on their website is silent about his education status, does not call him either “Dr.” or “Mr.”

– A 2004 Economist article, “Unix’s founding fathers”, refers to Dennis as “Dr. Ritchie”, does not reference his educational background.

– Dennis himself is non-committal on his Bell Labs biography page…

“I was born Sept. 9, 1941 in Bronxville, N.Y., and received Bachelor’s and advanced degrees from Harvard University, where as an undergraduate I concentrated in Physics and as a graduate student in Applied Mathematics. The subject of my 1968 doctoral thesis was subrecursive hierarchies of functions.”

– The Japan Prize (2011) webpage says that Dennis earned a “Ph.D. in Computer Science, Harvard University”, in 1968.

– And perhaps the best example of confusion comes from the Computer History Museum. David Brock broke the story that Dennis never received his doctorate. And yet, the Dennis Ritchie profile page on the CHM website (October 2021) states:

“Dennis Ritchie was born in Bronxville, New York, in 1941. He graduated from Harvard University with degrees in physics and applied mathematics and with a PhD in mathematics (1968).”

– In 1998, Dennis recorded an interview with Princeton professor Michael Sean Mahoney, as part of a larger project on the history of UNIX. The interview was wide ranging, lots of probing questions and detailed stories about the early days of grad school and early Bell Labs. The entire interview is great and worth reading. We have highlighted the “Grad school experience” questions and answers here. This part of the interview would have been a perfect opportunity for Mahoney to come out and directly ask Dennis, “So am I right that there is some story about your doctoral thesis?” But instead, you can see for yourself how Dennis is able to direct the conversation away from the topic without discussing his thesis or actual degree status.

It is not clear that Dennis ever talked with anyone about his thesis experience during his lifetime. No one among family, friends or professional colleagues, has any recollection of discussing the topic with Dennis. The sole exception to this was sister Lynn. She told David Brock in 2018:

“Late in life Dennis said, “Well, you know, I never actually got the piece of paper.” And we, I mean, it wasn’t an amazing surprise, but.. And he began to talk about it a little bit… I think he made some reference to, “Oh, it was just, you know, there was a lot of hassle involved, a lot of red tape.” And this would really, literally, only have been a few years before he died, I think.”

The story could well have died when Dennis passed in October 2011, except for one last tribute. In Spring 2012, Mauricio Cortes from Bell Labs wrote to the dmr sibs. The Labs was organizing a tribute to Dennis, “The Lasting Legacy of Dennis Ritchie”, for September 7th, and Cortes was preparing a document that would contain everything that Dennis had ever written. The project was going well except that he was having trouble finding a copy of Dennis’ doctoral thesis. Could we help?

It turned out that Lynn was able to help. She contacted Fischer’s widow Charlotte who still possessed Pat Fischer’s draft, which she retrieved and sent to Lynn who was then able to present the dissertation to Mauricio from the Dennis Day celebration stage. (We have since donated all of Dennis’ papers to the Computer History Museum.)

So the dmr thesis was found! And the story has continued to unfold…

In June 2020, David Brock published “Discovering Dennis Ritchie’s Lost Dissertation” on the Computer History Museum website. He describes what the thesis was actually about and why it was important, then tells the Albert Meyer library fee version of the kill story.

In Summer 2020, David Brailsford, University of Nottingham professor emeritas, working with Brian Kernighan and Chuck Bigelow, began the process of fully digitizing the entire dmr dissertation. Brailsford describes this project and what it entails, in a May 2021 video blog post on computerphile.

Brailsford is the first person to focus on the thesis typography. It turns out that many of the specialized symbol IBM Selectric type-ball fonts from the 1960s have not been converted to digital fonts, so Dave’s progress frequently was made character by character which brought him to great intimacy with the specific placement and positioning of each and every symbol. Brailsford’s quintessential quote from his blogpost about the dmr thesis:

“Dennis was five years ahead of his time and lord knows how he did it.”

In Fall 2020, brother Bill joined the Brailsford/Kernighan/Bigelow effort and started focusing on trying to explain how Dennis could have created the uniformly perfect typographic document that he did. These efforts are described in the “Anatomy of a Thesis” section, also much to be learned in “Young Adulthood” and “1960s Typing” sections.

Originally there was hope for a major historical revelation, a new story to add to the dmr legend. Dennis had a CTSS account at MIT during grad school, he had worked on Project MAC and was involved with Multics during his first months at Bell Labs fall 1967. His siblings remember that he had a IBM terminal with clacking ball (probably a 2741 terminal) in our family basement room, as well as WATS line and modem. We wouldn’t put it past him to figure out a way to type/store/print his dissertation electronically… the document itself was printed with tractor-feed precision. Could it be coincidence that starting so early Dennis was right there in the heart of the 1960s time sharing revolution? How could he not have used this knowledge to help with his thesis?

But experts and contemporaries have all counseled us not to make the argument that Dennis could have used a computer to produce his thesis. Typewriter / typographic technology moves in specific historical steps. By Spring of 1968, there were some elaborate new typographic technologies emerging, we cover these in the “1960s Typing” section of this website. But at that time there did not exist any system, anywhere, by which an electronic computer program could control line feeds and manage symbol swaps and otherwise assist with typing a complicated mathematical dissertation like Dennis’.

Plus, we can’t find a single Bell Labs colleague who can recall that Dennis revealed a specific interest in or experience with mathematical typography, from Brian Kernighan to Ken Thompson to Doug McIlroy to any of them.

And Dennis himself was opaque on the subject. Following is an excerpt from “The Evolution of the Unix Time-sharing System”, a paper he presented at the Language Design and Programming Methodology conference at Sydney, Australia, September 1979. Here he tells the story of how the first UNIX corporate assignment, in 1970-71, was to be a word processor for typing patent applications.

“In early 1970 we proposed acquisition of a PDP-11, which had just been introduced by Digital. … the charter sought was not merely to write some (unspecified) operating system, but instead to create a system specifically designed for editing and formatting text, what might today be called a `word-processing system.’ The impetus for the proposal came mainly from J. F. Ossanna, who was then and until the end of his life interested in text processing…

By the spring of 1971, it was generally agreed that no one had the slightest interest in scrapping Unix. Therefore, we transliterated the roff text formatter into PDP-11 assembler language, starting from the PDP-7 version that had been transliterated from McIlroy’s BCPL version on Multics, which had in turn been inspired by J. Saltzer’s runoff program on CTSS. In early summer, editor and formatter in hand, we felt prepared to fulfill our charter by offering to supply a text-processing service to the Patent department for preparing patent applications.”

It doesn’t appear here that he already went through this exercise five years before.

This is the reference that Dave Brailsford makes in his Computerphile video… that by all evidence Dennis’ thesis should have been powered by these software advancements, the document was so precise and consistent. But this story is from 1971, from Dennis’ own words it appears that he and the entire UNIX team were solving this typographic challenge for the first time.

So we’re left with four mysteries:

What happened to derail his thesis?
How was he able to suppress the story for his whole life?
How did he create such a typographic masterpiece?
Why did he not talk about his experience with mathematical typing to his Bell Labs colleagues?

Let’s finish off here with addressing Mystery 2. How was Dennis able to suppress the story of his thesis, suppress the fact that he did not have a doctorate, for his whole lifetime? We start by recognizing the fact that Dennis was a very private person. It is pretty well established with the computer science community that uncommonly little is known about Dennis’ personal life. This is well described in the 1991 UNIX World article, “Who is the Real Dennis Ritchie?”.

He wasn’t always withdrawn in this way. Lynn and David Brock discussed this in her 2018 interview:

Lynn: “He was always– I mean, I can remember, to my shame, really, feeling that I wish Dennis was more like the “All American Boy.” I mean, he was never athletic. And he was a little bit goofy and nerdy. But, you know, really the sweetest person on Earth.”

Brock: “Do you think, did Dennis have a circle of friends when he was young?”

Lynn: “Yeah, he did. There were a couple of friends in particular who lived nearby and again, I can remember seeing quite a lot of them. And so he did. I guess he didn’t hang out with them in the same way that maybe I would have been hanging out with my friends or John or Bill. But he definitely did…”

“And in those years, I mean, he was really just good fun. He hadn’t withdrawn in the way he sort of did later.”

Brock: “I wondered if the period of change where he became let’s just say more of a private person or an extremely private person… Did that happen do you think when he was in–while he was at Harvard, maybe, in his graduate studies days? Or was that after?”

Lynn: “I think it was after.”

As Lynn described, Dennis’ turn to privacy wasn’t simply passive, it could take the character of an active, assertive force.

“He hadn’t withdrawn in the way he sort of did later. And when I say “withdrawn” I mean, I think that if you wanted to talk to him about something, he was very capable of putting up a complete brick wall. And you always knew it. I mean, you couldn’t get through to that if he wasn’t in the mood to. A lot of body language. I mean, a lot of the times you would just know by the body language not to even try.”

Lynn called it a Brick Wall, John and Bill called it a Force Field. In his 2018 Brock interview, Bill inarticulately tried to describe the phenomenon as captured by the transcript:

“Dennis had this ability, you put up the force field and then you didn’t even– it was like otherworldly how he just– you were not– …”

Whatever it was, as family members we knew all about this special Dennis power. It was very personal to him, but we think it likely that it pervaded his whole life. Every one of his colleagues and acquaintances experienced the force, but because of its very nature no one could address it. When Steve Jobs died in October 2011 one of the stories we heard was that he had a Reality Distortion Field. Dennis, who died six days after Jobs, had a comparable power… his Deflection Force Field. Nobody knows about it because that’s its very nature. While it’s at the center of the “Who Is Dennis?” question, it is hard to explain without specific examples.

And now comes the story of the dmr thesis. This story is a big deal, the primary question being asked was whether Dennis was to be addressed as “Dr.” or “Mr.” by people who expected to get it right. We documented how the story kept shifting over time, as award presenters, magazine articles, interviewers all kept shifting stories. As late as 2011, the Japan Prize still claimed that Dennis had attained a doctorate.

This is evidence–the best evidence any of us will ever see–of the dmr Deflection Force Field. Almost certainly we’ll never learn the true story of what happened beyond the library fee, but almost certainly also, we can speculate that something must have happened to trigger Dennis’ Force Field into action. That’s all we got for now. Please keep coming back. There is more to be told and possibly we’ll find more answers that we can share.