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

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

Stack:

• Automatic allocation/deallocation.
• Limited size (typically 1-8 MB).
• Very fast (L1/L2 cache).
• LIFO order.
• Stores local variables, function parameters.

1void func() {
2    int x = 10;        // Stack
3    int arr[100];      // Stack
4    // Automatic cleanup on function exit
5}

Heap:

• Manual allocation (new/malloc).
• Large size (GB).
• Slower (main memory).
• Random access.
• Stores dynamic data.

1void func() {
2    int* ptr = new int(10);  // Heap
3    int* arr = new int[100]; // Heap
4    // Must manually delete!
5    delete ptr;
6    delete[] arr;
7}

When to use:

• Stack — small, short-lived data.
• Heap — large, long-lived, dynamic size.