Anyway, I'm sure fellow Metro-Obsessives will be as excited as I was at this - I noticed tonight in my local Asda that they've started rolling out a new style shelf-edge price label thing (not sure what they are technically called). God they're awful. They use that bizarre handwriting font that they use on a lot of their current signage, which is pretty hard to read at such a small size (example of said font in the image below below...)

They're still black on white, look incredibly cheap, and aren't a patch on the far-superior Sainsbury's equivalent.
I've always wondered, however, just how these work. Are they printed by those little machines that the shelf-stackers seem to carry around with them or something? They seem to come off a roll, as the edges are perforated. Given that supermarkets stock thousands of products, with constantly changing prices, how easy is it to keep them correct? I'm guessing the machines are linked to a computer somewhere which stores exactly what each label says or something?
Please respond.