What is a union in C?

A union in C is indeed a user-defined data type that allows for the storage of different data types in the same memory location. This means that a union can hold one of its specified data types at any given time, but all of these data types share the same memory space. The size of a union is determined by the size of its largest member, ensuring that you have enough space to store any one of the types defined in the union.

This feature is particularly useful when you want to save memory in scenarios where you know that only one of the data types will be used at a time. For example, if you have a union that can be either an integer or a float, the same memory will be allocated for both types, optimizing the memory usage while accessing one value at a given time.

Understanding this concept is crucial for effective memory management in C programming, particularly in embedded systems or applications where memory resources are limited.