Abstract: In last month's column I described the Internet and its uses. This month I talk about how computers communicate, different ways to connect to the Internet, and the software that makes the Internet easy to use. How Computers Communicate A lot of supposedly knowledgeable people forget to tell you the things in this section. Specifically, people often forget to tell you that your microcomputer does not have to act dumb when it is connected to another computer. They also forget to differentiate between how different software programs communicate. This isn't the most fun stuff to discuss, but it's probably the most important. Terminal-host communication. In the Sixties and early Seventies, time-sharing computers were common. Time-sharing was an apt name, since not everyone could use the computer at once. Users had to wait in an electronic line - called a queue - that was maintained by the computer. (In the early Seventies I used to do my computing on a university computer at 2 a.m. - the queue was shorter then.) Users would sit at a terminal and wait their turn to use the computing power of the host computer; thus these systems might be called terminal-host systems. No matter what it looks like, a terminal is nothing more than a monitor and keyboard for a host or remote computer. Everything on the monitor is controlled by the host - a terminal does not contain a processor. Sitting at a terminal in a building far away from a host is deceptive. It seems like the computer is in the workstation on your desk, but it isn't. The host manages the terminals and performs all computing. Terminal emulation programs (communications software). With the advent of personal computers (PCs) in the late Seventies and early Eighties, terminal emulation programs became common. Examples of common terminal emulation programs are White Knight, Procomm, Smartcom, Mac-Terminal, EZ-term, and the communications modules in programs like Microsoft Works and Windows. A terminal emulation program lets a PC serve as a terminal. Essentially, a terminal emulation program lets an intelligent microcomputer become a dumb terminal. Turning a personal computer into a dumb terminal is tricky, because the keyboards on the two kinds of devices are substantially different. Most terminals have special keys like Attn, Ctrl, EOL, and PF1 to PF12 - some of which are not common on microcomputer keyboards. Extended keyboards for Macs and PCs, which have 12 function keys, help out a lot but do not solve the problem entirely. My advice is always to order computers with extended keyboards. New terminal emulation program users have great difficulty with the keyboard problem. User-interface software packages. User-interface software packages are a recent (early Nineties) development. Examples include software disks supplied with a subscription to Compuserve, Prodigy, eWorld, and the National Geographic Kids Network online services. Typically these programs provide icons for each service or menu choice. Additionally, user-interface software programs may make the phone call to the remote host, assist in log-on and -off, and facilitate file transfer to and from the PC. User-interface software programs help one use a terminal to communicate with a host, but the local PC is still basically a dumb terminal. Host-host communication. In the late Sixties the U.S. Defense Department began developing a way for its various computers (hosts) in the U.S. and around the world to talk with one another. If a bomb destroyed the telephone line from one computer to another, the military needed a way to automatically reroute the connection. The military's solution was to enclose messages from one computer to another in small (or bundles), to give every packet an address, and to provide special use computers that did nothing but act as giant routers or switches for sending packets from place to place. Packet switching and addressing are important, since they allow one computer to communicate with another as a peer, thus breaking down the terminal-host arrangement. …
Publication Year: 1995
Publication Date: 1995-04-01
Language: en
Type: article
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Cited By Count: 1
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