Bar codes, familiar to us all as the black and white rectangular mark that enables products in a supermarket to be tracked, represent data using the spacing of parallel lines.

and, in the early hours of Sunday morning in the Hotel Europe's piano bar,Randi Zuckerberg, the “director of creative and buzz marketing” at Facebook(co-founded by her brother Mark).

Of course, nervousness can also generate over-talking. "We have a bar running along the bottom of the screen as you're being recorded to mark the passage of time," Bitting says.