Answer
A union is an aggregate type whose members overlap in the same storage. • Only one member value is normally stored at a time. • The union size is sufficient for its largest member, with required alignment. • Reading a member other than the last stored member has limited, type-dependent rules.
💡 C Example
union Number {
int integer;
double real;
};
union Number number = { .integer = 42 };
⚡ Quick Revision
A union lets different members share the same storage.