Static structures and dynamic structures differ fundamentally in terms of memory allocation, with static structures allocating memory at compile time and dynamic structures allocating memory at runtime.

To elaborate, static structures are characterized by a memory size that is predetermined during compile time. This means that the required amount of memory is established before the program is executed. Static memory allocation is commonly applied to arrays and similar data structures where the size is known in advance. Memory for these structures is typically allocated on the stack, a memory region that the compiler manages automatically. The primary advantage of static memory allocation is its speed, along with the elimination of memory leaks since the compiler automatically releases memory once it is no longer needed. However, a significant drawback is that the size of the structure cannot be altered after its definition, which may lead to inefficient memory usage if the allocated space is not fully utilized.

In contrast, dynamic structures allocate memory during runtime, meaning the required amount of memory is determined while the program is executing. This approach is particularly useful for data structures where the size cannot be predetermined, such as linked lists and trees. Memory for these structures is allocated on the heap, a memory area that is manually managed by the programmer. The key benefit of dynamic memory allocation is its flexibility, allowing the size of the structure to adjust as necessary. On the downside, dynamic allocation tends to be slower than static allocation, and there is a risk of memory leaks if the programmer neglects to free the memory once it is no longer needed.

In summary, the distinction between static and dynamic structures lies in the timing and method of memory allocation. Static structures allocate memory at compile time on the stack, while dynamic structures allocate memory at runtime on the heap. Each approach has its respective advantages and disadvantages, and the choice between them should be based on the specific needs of the program.