Systems fundamentals quick-fire: memory, processes, threads and transactions

A short screen of basics, answered out loud:

1. What an array is, how it is laid out in memory, and how it differs from a linked list.
2. What a smart pointer is and the kinds you know.
3. How processes and threads differ, and the risks of sharing memory between threads.
4. ACID and what a transaction guarantees.

Give a concrete example from your own work where you can.