13th February 2005, 5:30 PM
Exactly, the encoding is the same so there's really no way the scanners can tell the difference, which means there's no way a store can reject it. The last part, where it draws money from your account instead of charging it, is something the computers at the store doesn't even see, much less actually do. That's something the credit card company's computers do, so again, it's totally invisible to the store, and if it's totally invisible to them, then again, no way they can reject it.
"On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question." ~ Charles Babbage (1791-1871)