| Feature | Structure | Union |
|---|---|---|
| Definition | A structure is a user-defined data type that groups related data items under a single name. | A union is a user-defined data type similar to a structure, but it uses the same memory location for storing multiple variables of different types. |
| Memory Allocation | Each member of a structure is allocated its own memory space. | All members of a union share the same memory space, meaning the size of a union is the size of its largest member. |
| Accessing Members | Members of a structure can be accessed individually. | Only one member of a union can be accessed at a time. |
| Size | Size of a structure is the sum of sizes of all its members. | Size of a union is the size of its largest member. |
| Usage | Suitable for scenarios where multiple data items need to be stored together. | Useful when memory efficiency is critical, and only one member needs to be active at a time. |
| Memory Overlap | Members in a structure do not share memory. | All members in a union share the same memory location, leading to overlap. |
| Initialization | Each member of a structure can be initialized individually. | Only the first member of a union can be initialized during declaration. |
| Member Access | Members of a structure can be accessed simultaneously. | Accessing one member of a union will overwrite the values of other members. |
| Storage | Requires memory allocation for each member separately. | Saves memory by sharing memory space among members. |
| Use Cases | Ideal for representing complex data structures with multiple attributes. | Suitable for implementing variants or representing mutually exclusive data options. |
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