I'm thinking even more basic though. The human/computer
   interface. I just typed the letter a. Where is it? My finger to
   key. Down the circuits, up to the display, I see an a. Where
   does it live? It lives in RAM. Temporary buffer. It visually
   lives on the screen. *I can see it*. But: What happens if I make
   a mistake? What happens if there's a glitch? Javascript error?
   Internet connection error? Server error? It's gone. Where's my
   "a" go? Wiped out.