What is the Difference Between Structure and Union in C?

The main difference between a structure and a union in C lies in the way they allocate memory and store data. Here are the key differences:

1. Memory Allocation: In a structure, each member has its distinct storage location, and the total memory allocated is equal to the sum of the memory requirements of all members. In a union, all members share a single memory location, and only one member can be accessed at a time. The memory allocated to a union is equal to the size of its largest member.
2. Accessing Members: In a structure, you can retrieve any member at a time without affecting other members. In a union, changing the value of one member will affect the others, as they share the same memory location.
3. Usage: Structures are mainly used for storing various data types under a single unit, while unions are mainly used for storing one value at a time for all its members.
4. Flexible Arrays: Structures support flexible arrays, while unions do not.

Both structures and unions are user-defined data types in C that allow you to combine different types of data together as a single unit. They can contain various object types, including different structures, unions, arrays, and bit fields.

Comparative Table: Structure vs Union in C

Here is a table comparing the differences between structures and unions in C:

Both structures and unions are user-defined data types in C that allow you to group different data types together. However, they serve distinct purposes and have key differences in terms of memory usage and accessibility.