The concepts of OOP as you described are language independent.  What other languages support OOP?

Object-Oriented Programming with C++

One of the benefits of OOP that I would like to also point out is that the structure of object oriented code make it easier for us to debug.  We can write a class and at the same time write a test for that class (this is called extreme programming or test driven development).

D1A) The concepts of OOP as you described are language independent.  What other languages support OOP?

D1B) How does a client to this code access one of the private data members?

D2A) Is main() a function?  If so, who calls it?

D2B) Having a prototype allows us, as code readers, to see the big picture rather than the small details.