I walked into the Operating Systems classroom a half-hour early this morning, as is my usual habit. I greeted the prof, and then, noting that he had an assignment of mine in front of him, said "Oh. Speak of the devil!"
He looked a little puzzled, so I gestured to the open assignment. "You're marking my assignment" I prompted.
He shook his head, and said no. I tried again. "Oh. Then you're entering my marks."
Again he shook his head. "No" he said, smiling. "I'm using your assignment to mark everyone else's."