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An Interview with Bjarne Stroustrup

JB: When did you first become interested in computing, what was your first computer and what was the first program you wrote?

BS: I learned programming in my second year of university. I was signed up to do "mathematics with computers science" from the start, but I don't really remember why. I suspect that I (erroneously) thought that computing was some sort of applied math.

My fist computer was the departmental GIER computer. It was almost exclusively programmed in Algol-60. My first semi-real program plotted lines (on paper!) between points on the edge of a superellipse to create pleasant graphical designs. That was in 1970.

JB: When you created C++, was the object oriented programming (OOP) paradigm (or programming style) obviously going to gain a lot of popularity in the future, or was it a research project to find out if OOP would catch on?

BS: Neither! My firm impression (at the time) was that all sensible people "knew" that OOP didn't work in the real world: It was too slow (by more than an order of magnitude), far too difficult for programmers to use, didn't apply to real-world problems, and couldn't interact with all the rest of the code needed in a system. Actually, I'm probably being too optimistic here: "sensible people" had never heard of OOP and didn't want to hear about it.

I designed and implemented C++ because I had some problems for which it was the right solution: I needed C-style access to hardware and Simula-style program organization. It turned out that many of my colleagues had similar needs. Actually, then it was not even obvious that C would succeed. At the time, C was gaining a following, but many people still considered serious systems programming in anything but assembler adventurous and there were several languages that—like C—provided a way of writing portable systems programs. One of those others might have become dominant instead of C.

JB: Before C++, did you "just have to create C++" because of the inadequacy of other languages, for example? In essence, why did you create C++?

BS: Yes, I created C++ in response to a real need: The languages at the time didn't support abstraction for hard systems programming tasks in the way I needed it. I was trying to separate the functions of the Unix kernel so that they could run on different processors of a multi-processor or a cluster.

JB: Personally, do you think OOP is the best programming paradigm for large scale software systems, as opposed to literate programming, functional programming, procedural programming, etc.? Why?

BS: No programming paradigm is best for everything. What you have is a problem and a solution to it; then, you try to map that solution into code for execution. You do that with resource constraints and concerns for maintainability. Sometimes, that mapping is best done with OOP, sometimes with generic programming, sometimes with functional programming, etc.

OOP is appropriate where you can organize some key concepts into a hierarchy and manipulate the resulting classes through common base classes. Please note that I equate OO with the traditional use of encapsulation, inheritance, and (run time) polymorphism. You can choose alternative definitions, but this one is well-founded in history.

I don't think that literate programming is a paradigm like the others you mention. It is more of a development method like test-driven development.

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