Virtuals are minor problem

"A=B can mean network/disk access and more!"

In fact this is nonsense. C++ doesn't allow overloading of builtin types' operators. So you're not able to, i.e. redefine operator+ ( int , int ). So existing uses of operators will all work. Without operator overloads (in C), you wouldn't be able to do the equivalent at all. The way you'd have to do it in C would be:

A a;
B b;
C c;

c = addAandB ( a , b );

...and that function call could do anything.