A union is a special class type that can hold only one of its non-static data members at a time.

Summary of some common use cases of scope resolution operator.

Solve diamond problem.

Since C++11

(), {} and std::initializer_list

Understanding lvalue, rvalue, their references and const references.

Understand volatile from assembly perspective.

Since C++17

Choose enum class over enum for type safety.

Work with string efficiently.