C++: What is the difference between stack and heap?

Stack — automatic, fast, limited. Heap — manual, slow, large.

1void func() {
2    int x = 10;        // Stack
3    int* ptr = new int(20);  // Heap
4    // ptr automatically cleaned up on scope exit
5}

Stack:

• Automatic allocation.
• Limited size (~1-8 MB).
• Very fast.
• LIFO order.

Heap:

• Manual allocation.
• Large size (GB).
• Slower.
• Random access.