Seibel: Have you ever done pair programming?

Ingalls: I’m trying to think of examples. Usually I’ve been on my own orworking on a separate part. There are lots of projects on which I’ve workedwith others, and many intense pair debugging sessions.

Seibel: Are there any techniques for managing that kind of collaboration?When everybody goes off to each do their own work, there’s always thepotential of things not quite fitting together.

Ingalls: Either you agree on some interface, or often I’ll build someframework that’s incomplete but that works for one example and then it’sobvious to someone else where their stuff would fit in. Or they’ve donethat and it’s obvious to me where my stuff fits in. It’s usually been in thatconcrete way, rather than any kind of spec because we’ve usually beenworking on something that nobody wrote down. It’s all kind of beenfollowing the needs of the moment.

Seibel: You’ve worked at a lot of levels from down in the bits of BitBlt andwriting microcode up to fairly high-level stuff in Smalltalk. How much doprogrammers need to know about the various levels of software andhardware they’re dealing with?

Ingalls: That’s a good question. To think outside the box, you’ve got to bea little outside the box. If there’s something to be taken advantage of thatyou don’t see in your normal exposure to a language, then you’ve got tohave some intuition outside and some understanding of that and the abilityto work in a system that has control over that.

In the context of language design, maybe you’re going to want to work withthe processors that are out there so maybe you don’t need to know a lotabout them, other than, for decent performance, how caching works andthat kind of stuff. I think you have to stand back and say, “What boundariesis this going to cross?”

Seibel: Leaving aside how much you need to know eventually, when itcomes to learning to program, some people say you should start with ahigh-level language and learn certain universal concepts. Other people sayyou need to start with assembly and work your way up so you understandwhat’s going on. Do you buy that?

Ingalls: No, I don’t think I necessarily buy that. That’s how I learned it and Iwas fascinated with it. And I think there will always be people who arefascinated with this level or that. But I don’t think there’s any one way, justlike there’s any one way to do art.

I think there are other things that are equally exciting and probably moreappropriate nowadays still to be explored. Lord, we were thinking of doingartificial intelligence a quarter of a century ago. The machines areimmeasurably faster and we’re doing almost nothing in that space—we’restill doing very close to Fortran. Prolog has been out there for a long time;there’s all sorts of stuff that can be done with logic programs. If you oughtto learn about assembly and find out how that works, you ought to be doingsome immersion in things that are more outside the box and that are reallya possible piece of the future.

So I’m not saying, “not assembly language.” I’m saying, you should learnsome of these other powerful techniques so when you think about how togo forward, you can take advantage of them. In terms of a place to start,immediate gratification has always worked for me. When I want to teachsomebody Smalltalk, I usually start with a little dialog: “What interests youmost? Are you interested in how to play with text or things you can do withnumbers or things you can do with music, or things you can do withgraphics?” And start with any one of those.

There’s all kinds of fun stuff you can do taking text apart and putting ittogether. There’s all kinds of fun stuff you can do with numbers anddifferent bases and floating-point and fixed. And the same thing with music:you can start with notes and put them together in melodies and chords.And with graphics: superpositions and rotations. Any one of those is a richspace to explore. I really think different people think differently that way.Similarly, if you’re going to teach somebody to program a computer, maybeyou work with expression evaluation, maybe you work with logicprogramming. Maybe you do some stuff in user interface. People will light upin one area and that’s where they should go deep.

Seibel: As I understand it, the original purpose of Smalltalk was to teach akind of programming literacy. Is that something everyone should have, justthe way everyone is expected to be able to read and write and do a little bitof math? Should everyone have some ability to program a computer justbecause it’s a useful way of thinking?

Ingalls: It’s very hard for me to say that anyone should do anything, becauseI’ve met people that I think are better than me in this way or that way thatknow nothing about programming. In terms of literacy, the stuff that’s underthere is logic and math and yes, people should be able to think logically. ButI’d never say that somebody should know how to program, I don’t think.There’s stuff we do in everyday life that’s like programming. You need toknow about procedures with steps, that kind of thing.

Computers incorporate some powerful ideas and can bring some powerfulideas to life. The wonderful thing about computers is they bringmathematics to life. So they can be a great tool that way. Now, my feelingabout the powerful ideas that are necessary to lead a good life, it’s not clearhow many of them are in this space.

Seibel: Seymour Papert wrote in Mindstorms about debugging as animportant element of an intellectual toolkit—the idea that the name of thegame is not to get the right answer but to get an answer and then debug it.

Ingalls: Oh, absolutely! People should learn to think clearly and toquestion. And to me it’s very basic. If you grow up in a family where whenthe cupboard door doesn’t close right, somebody opens it up and looks atthe hinge and sees that a screw is loose and therefore it’s hanging this wayvs. if they say, “Oh, the door doesn’t work right; call somebody”—there’s adifference there. To me you don’t need any involvement with computers tohave that experience of what you see isn’t right, what do you do? Inquire.Look. And then if you see the problem, how do you fix it? To me that’s sobasic and human and comes so much from parent to child.

Computers are certainly a medium for doing that. But they’re justcomputers. There’s a lot of that that will transfer, but to me it’s really bigand basic and human, so it’s not like we’re going to enlighten the world justby teaching them computers.

Seibel: Do you remember the first interesting program you wrote?

Ingalls: Oh, let’s see. In each programming experience, there wassomething that was out of the box. When I discovered VisiCalc, I wrote aspreadsheet to translate English to pig Latin in VisiCalc. That was, to me,interesting, because it used the spreadsheet metaphor as a parallelprogramming approach. Parsing text that way was fun and enlightening.

Seibel: So VisiCalc had primitives for taking apart strings?

Ingalls: Yeah, you could take apart strings. Maybe what I actually had wasLotus 1-2-3, not VisiCalc, because I’m not sure that VisiCalc had stringprimitives. I got one of those little Poqet PCs—it was the first trulyhandheld PC. It ran on two penlights, and I put 1-2-3 on it, and I had a planeflight across the country and I thought, “What can I do in this time?”

Seibel: That must’ve been well after you learned to program, becausethere obviously weren’t Poqet PCs when you were starting out.

Ingalls: That was later on. The really interesting thing that I did in Fortranwas I got a hold of Val Schorre’s paper on META II—just a wonderful, reallysimple compiler compiler and wrote an implementation of that in Fortran.So all of a sudden this meant you could have other languages in a Fortran onlyenvironment. That was the most interesting thing I did in Fortran,because it used Fortran to escape from the world of Fortran.