Several questions in the programmer's interview guide

1. How can c ++ prevent a class from being instantiated?

A: use an abstract class, or define the constructor as private.

2. When is the constructor declared as private?

A: for example, to prevent the compiler from generating the default copy constructor

3. When will the compiler generate the default copy constructor?

A: As long as you have not written it, whenProgramWhen needed, it will generate

4. If you have already written a constructor, will the compiler still generate a copy constructor?

A: Yes