Monetary Systems

I have been reading different books and they all have different monetary systems. It is interesting to think about. Everyone needs a system to exchange goods and services even if they don't use paper or coin money. A system of credits can be used but it is hard to track without using something physical. If everyone had a hand held device, credits could be tracked by computer. Thus doing away with physical pieces of money. We almost do this now with debit cards, not everyone even accepts cash anymore.
Only half an inch of rain in our area. My grandmother, Nana, lives 15 miles to the south west and she received an extra 3/4 inch last Thursday.