How is design using C different from C++?

A employer is looking for C programmers, and I’m told they say that …

Good C design isn’t the same as good C++ design

… and so they’re looking for candidates experienced with C and not only C++.

How is the design of a large C system (hundreds of thousands or millions of lines of code) very different from that of C++?

Are the skills required of a developer very different, what differences should an experienced developer expect?

I’ve read Why are most Linux programs written in C? — including Linus’ little “two minute hate” at — but that doesn’t answer my question, which might be, “How is a well-designed C system unlike well-designed C++?” Or are they similar, and is Linus’ argument all there is to it?

I read Lakos’ Large-scale C++ Software Design — is there anything at all like that for C?

I’m trying to write this such that it isn’t a duplicate of:

Please assume I already know the differences between the langages.

I used C in the early 90s (before C++ became popular on PCs), and for writing device drivers on Windows (in the kernel where the C++ run-time library wasn’t supported), and I learned C++ incrementally as a superset of C.

IMO there’s obvious mapping between C and C++, like what’s written in one can be written in the other, for example:

  • C — a “file pointer” or “file handle”, plus an API of related functions which take a handle-or-pointer as a parameter, plus an underlying data structure (possibly hidden/encapsulated) which contains state associated with each handle
  • C++ — ditto except that “data structure” and “associated functions” and encapsulated in a class, as data members and methods

C++ has additional syntactic and type-checking sugar (e.g. templates and operator overloading), and its destructors allow RAII and reference-counting smart pointers, but apart from that …

And C has no first-class/language support for polymorphism, but e.g. a device driver on Windows is an installable plug-in, which has entry points which it exports, more or less like a vtable.

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Author: ChrisW