Answer by Brian for Should I stop using the term C/C++?

In general the SO users ask the person who is asking the question to choose a language: C or C++. Why?

There are many subtle differences between C and C++. For example, in C++, a const variable at global scope has internal linkage unless declared extern, but in C it has external linkage unless declared static. By saying "C/C++", the OP is asserting knowledge that the answer to their question is the same in both C and C++, when it very well might not be. This needlessly makes things harder for would-be answerers.

• Sometimes we can spot that the code isn't valid in one language or the other (for example, implicit conversions from void* to pointer to object are not valid in C++). This is annoying. Why are you saying "C/C++" when you have a piece of code that's valid in C but not C++? Did you intend C, or is this just an error in code intended to be C++?

• Sometimes the answer will be different depending on the language (for example, variable-length arrays exist in C99 but not in C++). If we don't know what language you're talking about, either we have to guess, or write an answer for both when only one will actually be useful, because you know which language you're actually using; you're just not telling us!

• Sometimes the answer really is the same for both languages, but it's hard to be sure. For example, I think C and C++ have the same integer conversion rules, but in order to be really, really sure, I have to read both standards carefully. Again, this makes me do twice as much work as necessary when you probably only care about one of the languages.

Anyway, to answer your other questions:

1. Yes.

2. If you are linking together C and C++ code, it is acceptable to use both tags, but please specify which language each file is in.

3. There are breaking changes sometimes, but they're rare and typically limited in impact (otherwise they don't get approved). For example, auto in C++11.

4. I don't think they directly collaborate, but they pay attention to developments in the other language and try to avoid introducing changes that would make compatibility more difficult.

And if you really do want to know about both languages, that's fine, and you can say that in your question. When you say "C/C++", I'm really not sure what you mean, and it really looks like you're making an assumption about the two languages.