COMPUTERS Part 1
Generally, a computer is any device that can perform numerical calculations--even an adding machine, an abacus, or a slide rule. Currently, however, the term usually refers to an electronic device that can perform a series of tasks according to a precise set of instructions. The set of instructions is called a program, and the tasks may include making arithmetic calculations, storing, retrieving, and processing data, controlling another device, or interacting with a person to perform a business function or to play a video game. Today's computers are marvels of miniaturization. Machines that once weighed 30 tons and occupied warehouse-size rooms now may weigh as little as 3 pounds (1.4 kilograms) can carried in a suit pocket or a purse. The "brains" of today's computers are integrated circuits (ICs), sometimes called microchips, or simply chips. These tiny silicon wafers can each contain millions of microscopic electronic components and are designed for many specific operations. Some chips make up a computer's central processing unit (CPU), which controls the computer's overall operation; some are math coprocessors that can perform millions of mathematical operations per second; and others are memory chips that can each store more than 16 million characters of information at one time. In 1953 there were only about 100 computers in use in the entire world. Today hundreds of millions of computers form the core of electronic products, and programmable computers are being used in homes, schools, businesses, government offices, and universities for almost every conceivable purpose Computers come in many sizes and shapes. Special-purpose, or dedicated, computers are designed to perform specific tasks. Their operations are limited to the programs built into their microchips. These computers are the basis for electronic calculators and can be found in thousands of other electronic products, including digital watches (controlling timing, alarms, and displays), cameras (monitoring shutter speeds and aperture settings), and automobiles (controlling fuel injection, heating, and air conditioning and monitoring hundreds of electronic sensors). General-purpose computers, such as personal computers and business computers, are much more versatile because they can accept new programs. Each new program enables the same computer to perform a different set of tasks. For example, one program instructs the computer to be a word processor, another instructs it to manage inventories, and yet another transforms it into a video game. Although some general-purpose computers are as small as pocket radios, the smallest class of fully functional, self-contained computers is the class called notebook computers. These usually consist of a CPU, data-storage devices called disk drives, a liquid-crystal display (LCD), and a full-size keyboard--all housed in a single unit small enough to fit into a briefcase. Today's desktop personal computers, or PCs, are many times more powerful than the huge, million-dollar business computers of the 1960s and 1970s. Most PCs can perform from 150 to 400 million operations per second, and some can even perform more than 500 million. These computers are used not only for household management and personal entertainment, but also for most of the automated tasks required by small businesses, including word processing, generating mailing lists, tracking inventory, and calculating accounting information. The fastest desktop computers are called workstations, and they are generally used for scientific, engineering, or advanced business applications. Servers are fast computers that have greater data processing capabilities than most PCs and workstations and can be used simultaneously by many people. Often several PCs and workstations are connected to a server via a local area network (LAN). The server controls resources that are shared by the people working at the PCs and workstations. An...
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