Begun in the late 1960s by Pentagon weapons researchers as a system for easing communication between computers in disparate electric networks, the Internet has evolved (1) ______ into a popular vehicle for scientific research, communication, entertainment, and more. It links together thousands of computer networks such as those belonging to corporations, (2) ______ commercial services, universities, and research centers, joining them as branches on a tree to larger networks known as backbones. Once a computer is on-line, that is, connected by modem or networking equipment of the Internet, the user can search through data banks (3) ______ for documents, chat with other computer users, or instant send opinions and observations (4) ______ to the likes of President Bill Clinton, film critic Roger Ebert, or rocker Billy Idol (just to name a few). No central governing body runs the Internet, and nobody has an exact census of (5) ______ users. But estimates of the number already range from around 10 million to as high as 5 million. Well over 10,000 separated computer networks are connected by the Internet, and (6) ______ total traffic was expected to double during 1993. Today, the Internet is free resources and commercial services that provide databases and computer files with a fee. Publishers are (7) ______ seeking to make books and periodicals available on the Internet as a profit-making adventure (8) ______ Meanwhile, works in the public domain have begun appearing on the Internet for users to "upload" to their computers virtually free of charge. With electronic access to data (9) ______ from all over the world, scholarly research that in the past would have required months of travel could now be done at one’s desk. (10) ______