C++/C Federation and enumeration

Union Union

1. The address of a union variable is the same as any member address of a union variable.

2. Union variables of the same type cannot be compared in size.

3. Constructors and destructors can be defined, but cannot have virtual and static member functions, and cannot be used as base or derived classes.

Enum enum

1. Enumerations can define the same values.

2. This value is unknown when the integer is strongly converted to an enumeration and exceeds the enumeration value.

3. Anonymous enumeration is equivalent to directly defining const symbolic constants.

A fixed size of int,c++ is not fixed in the 4.C language.

C++/C Federation and enumeration