As recently as three decades ago, many Americans believed that using credit was an unwise and dangerous way to pay for what they bought.Some even thought that owing money to a store or a credit company was something to be ashamed of.Good citizens, they believed, always bought what they wanted with real money and they paid the full price immediately. 　　Today, however, all that has changed.Credit, as some observers have noted, has become a way of life in the United States.More and more Americans now are depending on those small pieces of plastic, credit cards, to pay for large purchases such as televisions, record players or furniture.Many people today would consider it unusual not to use a credit card to pay for a costly restaurant dinner, a hotel room or an airline trip.And there are some situations in which Americans must have credit cards.If they want the temporary use of a car, for example, they first must give the car rental company the number of their credit card.That number is considered a guarantee that they will return the car and pay for using it. 　　Credit cards offer two major services to Americans.First of all, they are easier and safer to carry than large amounts of money.Second, they permit people to borrow, to have the immediate pleasure of owning something, even if they do not have enough money to pay for it at the time. With credit cards people pay for goods or services at the end of each month instead of when they buy them.And when the time does come to pay, most credit cards offer people a choice.They can pay all of what they owe for the month or they can just pay usually between 5 and 10 percent of what they owe.