Can we have functions inside functions in C++?

Question

I mean something like:

int main() 
{
  void a() 
  {
      // code
  }
  a();

  return 0;
}

Answer 1

No, it's not allowed. Neither C nor C++ support this feature by default, however TonyK points out (in the comments) that there are extensions to the GNU C compiler that enable this behavior in C.