Generally speaking, one uses the / in english discourse to denote an ambivalent or between closely-related items. In other words, I know there is no 'C/C++' as a single entity -- it was 'C or C++, whichever or both'.

That was a very long diatribe about something which is obvious to every developer I know.

Besides, according to the site you link:

Do not refer to "C/C++." Some people get testy about that, and will (unfortunately!) ignore everything else you say just to correct you with something like, "There is no such language." It borders on pathetic, but you'll probably be okay if you say "C or C++" instead of "C/C++." Sigh.

Emphasis mine. :-)