根据内容回答下列各题，The home computer industry has been growing rapidly in the United States for the last ten years. Computers used to be large, expensive machines that were very difficult to use. But scientists and technicians have been making them smaller and cheaper while at the same time they have been made easier to use. As a result, their popularity has been increasing as more people have been buying computers for their homes and businesses. Computers have been designed to store information and compute problems that are difficult for human beings to work out. Some have voices that speak with the operators. Stores use computers to keep records of their inventories (库存货物) and to send bills to their customers. Offices use computers to copy letters, record business and keep in touch with other offices. People have been using computers in their homes to keep track of the money they spend. One important new use for computers is for entertainment. Many new games have been designed to be played on the computers. People of all ages have been playing these games. People also have been buying home computers to play computer games, watch movies and listen to concerts at home. They have become very popular indeed. Computers used to _______.