An anonymous union does not have a union name (tag) and its elements can be accessed directly without using a union variable.
For example,
union {
int i;
char ch[2];
};
Both i and array ch[] share the same memory locations and can be accessed directly simply by saying
i = 10;
ch[0] = 'A';
Simply omitting the union name in declaration does not make the anonymous union. For an union to qualify as an anonymous union, the declaration must not declare a variable of the union type.
Similarly, we can build anonymous enums as shown below:
enum {first, second, third};
int position = second;
The stream I/O classes define several anonymous enumerated types.
