Guy Steele

Guy Steele is a true programming polyglot. When I asked him what languages he has used seriously he came up with this list: COBOL, Fortran, IBM 1130 assembly, PDP-10 machine language, APL, C, C++, Bliss, GNAL, Common Lisp, Scheme, Maclisp, S-1 Lisp, ^*Lisp, C^*, Java, JavaScript, Tcl, Haskell, FOCAL, BASIC, TECO, and TeX. “Those would be the main ones, I guess,” he added.

He had a hand in the creation of both of the major surviving general-purpose Lisp dialects: Common Lisp and Scheme. He served on the standards bodies that defined Common Lisp, Fortran, C, ECMAScript, and Scheme and was recruited by Bill Joy to help write the official language specification for Java. He is now at work designing Fortress, a new language for high-performance scientific computing.

Steele’s academic career included an AB from Harvard and an SM and PhD from MIT. While at MIT he collaborated with Gerald Sussman on a series of papers now known as “The Lambda Papers,” which included the original definition of the Scheme programming language. He has also been a chronicler of hacker culture as one of the original compilers of the Jargon File and editor of the book version, The Hacker’s Dictionary (subsequently updated and expanded by Eric S. Raymond as The New Hacker’s Dictionary). And he played an important role in the birth of Emacs and was one of the first programmers to port Donald Knuth’s program TeX.

Steele is a Fellow of the Association for Computing Machinery and the American Academy of Arts and Sciences and a member of the U.S. National Academy of Engineering. He won the ACM’s Grace Murray Hopper Award in 1988 and Dr. Dobb’s Excellence in Programming Award in 2005.

In this interview he talks about designing software and the relation between writing and programming, and he gives one of the best explanations I’ve ever heard of the value—and limitations—of formal proofs of correctness.

Seibel: How did you get involved in programming?

Steele: Well, when I was in elementary school I remember being fascinated by science and math and I read books such as Irving Adler’s House of Numbers; it was one of my favorites. And I liked kiddie science fiction like, say, the Danny Dunn series and that kind of thing. So I had this general interest in science and math. In reading everything I could about science and math, I read a little bit about these newfangled computers that were coming up as well.

Seibel: And when would that have been?

Steele: I was in elementary school from 1960 through ’66. But I think the real turning point was when I got to Boston Latin School—it would have been in the equivalent of the ninth grade. A friend asked me, “Have you heard about the new computer in the basement?” I thought this was the newest story after the one about the fourth-floor swimming pool and the school only has three stories. But he said, “No really, it exists.”

It turns out that T. Vincent Learson had arranged for an IBM 1130 minicomputer to be in the basement of the Boston Latin School. He was an alum and a very generous one apparently. My friend proceeded to show me a Fortran program of about five lines and I was immediately fascinated.

Then I went to one of our math teachers and asked if I could have some books to study. He gave me some books and thought they’d keep me busy for a month but they actually lasted a weekend. I taught myself Fortran over Thanksgiving weekend—so it was a long weekend—of 1968. After that I was completely hooked.

My Latin School friends and I had a fascination with IBM because of the IBM 1130 and we took to visiting the IBM office downtown every couple of months and talking with the people there and occasionally ordering publications with what little money we had.

There was also a bookstore downtown that had books about exotic languages like PL/I, and we’d occasionally buy books there. So, through Latin School we got to know IBM equipment. We just had the 1130 but we drooled over System 360. We read about it and didn’t really have access to one.

Then I became involved at MIT in the spring of 1969 in the High School Studies Program. This was great—go on Saturday mornings and have college students teach you all this cool stuff. I took courses in group theory and computer programming and I forget what all else. I became rather heavily involved and therefore got to feel on very familiar turf at MIT. Through the High School Studies Program, we had access to both IBM 1130s and DEC PDP-10s. So that’s how we got to know the Digital Equipment line.

As high-school students we became aware of the DEC office in Central Square that tended to cater to the MIT students. They didn’t blink when high-school students walked in and asked for reference manuals. It was great. When I was a junior or senior at Latin School, a friend of mine and I typed up a proposal to DEC to implement an APL for the PDP-8. And they took the proposal seriously. They looked at it for a week and then they said, “Well, we don’t think this is a good idea, but thanks for the offer.”

Seibel: What was the first interesting program you wrote?

Steele: Well, I learned Fortran first so I think things really got interesting when I started to learn IBM 1130 assembly language. And I guess the earliest interesting program I can remember was something that would generate keyword-in-context indexes. IBM provided these so-called quick indexes for their manuals that, given a keyword, you could look it up in the index and it was alphabetized according to keyword but on either side of the keyword you would see several other words of context surrounding that word.

Seibel: Context from where the word appeared?

Steele: Where the word had appeared in the original publication. So down the middle column were the words that had been alphabetized and sticking out on either side would be chunks of context. So I thought I’d tackle that problem, doing it on the 1130. And considering that the 1130 had only 4,000 words of memory, it was clear that I was going to have to keep the records on disk. So I took this opportunity to learn about efficient out-of-core sorting techniques. What was interesting about this program was not so much the generation of the KWIC index but implementing a multiway out-of-core merge sort. And it was reasonably effective. Unfortunately my in-core sort was bubble sort because I wasn’t that sophisticated. I should have also done a merge sort in core but I hadn’t quite figured that out at the time.

Seibel: How long do you think it was from when you first realized there really was a computer in the basement to when you were writing this program? Was it months? Weeks?

Steele: It would have been within the first two years. I don’t remember whether it was in the first year. I learned Fortran in the fall of ’68. And I remember that APL was my third language so I must have learned the assembly language somewhere around Christmastime or shortly after. I know I learned APL in the spring of ’69 because that’s when the Spring Joint Computer Conference came to Boston.

IBM had an exhibit on the show floor touting all manner of IBM products but the APL 360 in particular, and I hung around that booth. At the end of the trade show they were about to throw the stack of paper away that had been used for demos on the Selectric terminal. At just the right moment I walked up and asked, “Are you going to throw that away?” And the lady looked at me, puzzled, and said, “Here, it’s yours,” as if she was giving me this big Christmas present. Which she was.

Seibel: What was on that paper?

Steele: It was fan-fold paper from a Selectric terminal on which they had been demonstrating APL for the past two days. Just little programming examples of whatever they had happened to type in. And from that and the brochure they had on the trade-show floor, I taught myself APL.