Discovering Dennis Ritchie’s Lost Dissertation - CHM

Home CHM BLOG From the Collection

Discovering Dennis Ritchie’s Lost Dissertation

By David C. Brock |<br>June 19, 2020

Share

Many of you, dear readers, will have heard of Dennis Ritchie. In the late 1960s, he left graduate studies in applied mathematics at Harvard for a position at the Bell Telephone Laboratories, where he spent the entirety of his career. Not long after joining the Labs, Ritchie linked arms with Ken Thompson in efforts that would create a fundamental dyad of the digital world that followed: the operating system Unix and the programming language C. Thompson led the development of the system, while Ritchie was lead in the creation of C, in which Thompson rewrote Unix. In time, Unix became the basis for most of the operating systems on which our digital world is built, while C became—and remains—one of the most popular languages for creating the software that animates this world.

Unix creators Ken Thompson and Dennis Ritchie. Original source unknown.

On Ritchie’s personal web pages at the Labs (still maintained by Nokia, the current owner), he writes with characteristic dry deprecation of his educational journey into computing:

“I . . . 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. My undergraduate experience convinced me that I was not smart enough to be a physicist, and that computers were quite neat. My graduate school experience convinced me that I was not smart enough to be an expert in the theory of algorithms and also that I liked procedural languages better than functional ones.”1

Whatever the actual merits of these self-evaluations, his path certainly did lead him into a field and an environment in which he made extraordinary contributions.

"Everything but bound copy"

It may come as some surprise to learn that until just this moment, despite Ritchie’s much-deserved computing fame, his dissertation—the intellectual and biographical fork-in-the-road separating an academic career in computer science from the one at Bell Labs leading to C and Unix—was lost. Lost? Yes, very much so in being both unpublished and absent from any public collection; not even an entry for it can be found in Harvard’s library catalog nor in dissertation databases.

After Dennis Ritchie’s death in 2011, his sister Lynn very caringly searched for an official copy and for any records from Harvard. There were none, but she did uncover a copy from the widow of Ritchie’s former advisor. Until very recently then, across a half-century perhaps fewer than a dozen people had ever had the opportunity to read Ritchie’s dissertation. Why?

In Ritchie’s description of his educational path, you will notice that he does not explicitly say that he earned a PhD based on his 1968 dissertation. This is because he did not. Why not? The reason seems to be his failure to take the necessary steps to officially deposit his completed dissertation in Harvard’s libraries. Professor Albert Meyer of MIT, who was in Dennis Ritchie’s graduate school cohort, recalls the story in a recent oral history interview with CHM:

“So the story as I heard it from Pat Fischer [Ritchie and Meyer’s Harvard advisor] . . . was that it was definitely true at the time that the Harvard rules were that you needed to submit a bound copy of your thesis to the Harvard— you needed the certificate from the library in order to get your PhD. And 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 the library wanted to have it bound and given to them. And the binding fee was something noticeable at the time . . . not an impossible, but a nontrivial 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 PhD. So he was more than ‘everything but thesis.’ He was ‘everything but bound copy.’”2

While Lynn Ritchie’s inquiries confirmed that Dennis Ritchie never did submit the bound copy of his dissertation, and did not then leave Harvard with his PhD, his 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.” We will never really know the reason, and perhaps it was never entirely clear to Ritchie himself. But what we can know with certainty is that Dennis Ritchie’s dissertation was lost for a half-century, until now.

Dennis Ritchie (right) around the time he started working at Bell Laboratories, with two other figures...