Question: What is the difference between C and C++?
Bjarne Stroustrup: C has the basic mechanisms for expressing computations. It has iterations, it has data types, it has functions and that’s it. It doesn’t get into the game of expressing abstractions. So if I want a matrix in C, I would have to say, I want an array and then I want a whole bunch of arrays and when I want to get the third element I have to program my way down to the third element of the fourth row or something like that.
In C++ you can define something, call it a matrix, you define a subscript operator. If you don’t want rectangular matrixes you can get pentadiagonal matrices, triangular matrices that’s the kind of stuff that people... the expert in that field are interested in. And you build that set of concepts and then you program it directly. It’s easier to program, it’s easier to debug and sometimes it’s even easier to optimize for performance when you are expressing the notions at the higher level, at the level where an expert in the field operates, rather than trying to have the expert in the field, say the physicist, also be an expert in dealing with the hardware, with the computer. There are fields still where you have to have a physicist and a computer scientist to get the work done, but we would like to minimize those because the skill sets are not the same. So you want to lift from the hardware towards the human level.
Question: Is C obsolete?
Bjarne Stroustrup: This is somewhat controversial. I think it is obsolete. I think the languages should have been merged into one, so that C would have been a subset of C++ instead of nearly a subset of C++. And then people could have used whatever parts of the C++ tool set they needed. As it is now, there are still enough incompatibilities that you have to remember which language you’re writing in, and I don’t think that is necessary. It appears to be a historical necessity, but it is not a technical necessity.
I’ve argued for compatibility, very strong compatibility, all the time. I mean, I started working on C++ three doors down from Dennis Ritchie and we were talking every day. The competition and tension that has been between C and C++ over the decades certainly didn’t come from home.
Dennis Ritchie wrote that first book that Brian Carnahan, now I’ll have dinner with Brian next week. We’re still very good friends as we’ve always been, but sometimes the programmers of the languages don’t quite see it that way. It should have been one language.
Recorded August 12, 2010
Interviewed by Max Miller