In the future, paper money may be replaced with digital currency. Digital files that have monetary value would be transferred between computers, to effect transactions. A digital file that represents a dollar is understood by the users of the system to have a value of one dollar, so the digital dollar can be used as legal tender for common transactions. But digital dollars are capable of providing functions that ordinary paper dollars cannot provide. Digital dollars can be programmed so they perform special functions, such as boycotts.
As an example of how flexible digital currency can be, let's consider how an economic boycott could be established with digital currency. Suppose there was a company that was unpopular, and you wanted to boycott that company. You could program you digital dollars so that they cannot be transferred to the company that is being boycotted. You could also program you digital dollars to limit how they are spent. For example, suppose you have a teenage son, and you want to give him an allowance, but you don't want him to buy certain things with his allowance. Specifically, you don't want him to buy alcohol, tobacco, or pornography. The digital dollars that you give to your son can be tagged with digital tags. Each digital dollar would be tagged with an anti-alcohol tag, an anti-tobacco tag, and an anti-pornography tag. If your son tried to buy any of these restricted itmes at a store, the stores's digital cash register would refuse to accept his money. You could prevent certain types of transactions simply by re-programing the digital currency.