Transcription: You can use a union in specific circumstances. For instance, when you want to conserve storage and you never use more than one member of a class at a time, or when you want to interpret the same stored data as having more than one data type. The data members overwrite each other in memory and the size of a union is the size of its largest data member. As you can see, a union can have data members and member functions and private, protected or public members. By default, all members of a union are public.