[originaltext] One hundred and thirteen million Americans have at least one

One hundred and thirteen million Americans have at least one bank-issued credit card. They give their owners automatic credit in stores, restaurants, and hotels at home, across the country, and even abroad, and they make banking services available as well. More and more of these credit cards can be read automatically, making it possible to withdraw or deposit money in scattered locations, whether or not the local branch bank is open. For many of us the "cashless society" is not on the horizon—it’s already here.
    While computers offer these conveniences to consumers, they have many advantages for sellers too. Electronic cash registers can do much more than simply ring up sales. They can keep a wide range of records, including who sold what, when, and to whom. This information allows businessmen to keep track of their list of goods by showing which items are being sold and how fast they are moving. At the same time these computers record which hours are busiest and which employees are the most efficient, allowing personnel and staffing assignments to be made accordingly. And they also identify preferred customer for promotional campaigns. Numerous other commercial enterprises, from theaters to magazine publishers, from gas and electric utilities to milk processors, bring better and more efficient services to consumers through the use of computers.
16. What does the credit card enable its owner to do?
17. What is true of the cashless society for many Americans?
18. What is this passage mainly about?