Note, however, that it is passing the address of the letter to convert_to_upper, not the letter itself.

But eventually you have this bearer note that you start passing around to spend to other people and they start to think of them as money and that's the origin of banking.

You take care not to step on the heels of the woman in front of you on the way out of the subway, and you might take passing note of her most excellent handbag.