What is the difference between stack memory and heap memory, and why is their usage often separated?

Stack and heap are two different areas of memory used for storing data during program execution.

Stack is a memory area where local variables and function call information are stored. It operates on the LIFO (last in, first out) principle. The stack has a limited size and is managed automatically: memory is allocated for local variables when entering a function and released upon exit.

Heap is a memory area for dynamic memory allocation, such as objects and data structures whose size may be unknown at compile time. Memory in the heap is allocated and freed manually (or with a garbage collector).

The separation is used for optimization and security:

• The stack is fast and ordered, suitable for temporary data with a short lifespan.
• The heap is flexible, allowing storage of data with a dynamic lifespan, but is slower and requires management.

Example in Java:

void example() {
    int a = 10; // stored on the stack
    int[] arr = new int[5]; // object on the heap, reference on the stack
}