Explain the differences between stack data structure and heap memory area.

A stack is a data structure that operates on the LIFO (Last In, First Out) principle. In programming, a stack is often used to store local variables and manage function calls. It is organized as a memory area with a fixed size, where data is added and removed only from one end — the top of the stack.

Heap is a region of dynamic memory used for storing objects and data whose size and lifetime are unknown at compile time. Memory in the heap is allocated and freed dynamically, usually with functions like malloc/free in C or new/delete operators in C++.

Main differences:

• Memory management: The stack is managed automatically (for example, local variables are deleted when a function exits), while the heap requires explicit management or a garbage collector.
• Size: The stack is usually limited in size, whereas the heap is much larger and more flexible.
• Speed: Operations on the stack are faster because they are just pointer adjustments, while heap operations are slower due to searching for free blocks.

Example usage in iOS:

• Local variables and function parameters are stored on the stack.
• Objects created dynamically in Objective-C and Swift are placed on the heap.