1. What the stack and heap are conceptually
2. What typically lives on the stack vs the heap
3. Value types vs reference types
4. Pure stack value types
5. Heap-backed value types and copy-on-write (COW)
6. Reference types and heap allocation
7. ARC’s relationship with heap memory
8. Performance implications of stack vs heap
9. Real Swift/iOS scenarios where stack vs heap matters

1. What the Stack Is

The stack is a fast, automatically managed memory region used for:

• Function calls
• Local variables
• Value-type storage (when possible)

Stack memory is:

• Scoped
• Thread-local
• Allocated and freed automatically