electronic device that can receive a set of instructions, or program, and then carry out these instructions by performing calculations on numerical data or by compiling and correlating other forms of information.
The modern world of high technology could not have come about without the invention of the computer. Computers are used throughout society for the storage and handling of data—from secret governmental files to banking transactions to private household accounts. Computers have opened up a new era in manufacturing through the techniques of AUTOMATION, (q.v.), and they have enhanced modern COMMUNICATION, (q.v.) systems. They are essential tools in almost every field of research and applied technology, from the construction of models of the universe to the production of tomorrow’s weather reports, and their use has in itself opened up new areas of conjecture. DATABASE, (q.v.) services and computer networks make available a great variety of information sources.
Computers come in a wide range of sizes. Supercomputers (see SUPERCOMPUTER,) analyze massive, complexly interrelated sets of data. For example, they solve problems in aerodynamic design of supersonic aircraft, predict the weather, and come up with new designs for disease-specific drugs. Mainframe computers and their smaller cousins, minicomputers, are the workhorses of commerce and industry. These centralized machines maintain records, calculate payrolls, and analyze statistics, among many other jobs.
The familiar PERSONAL COMPUTER, (q.v.), also known as a PC, desktop computer, or microcomputer, is used for word processing, accounting, and record keeping in businesses and homes. In business and industry, employees use PCs for their everyday work and to access other computers, larger or more specialized, for work of greater complexity. Increasingly, PCs are also an instrument of communication and information gathering through the INTERNET, and the WORLD WIDE WEB (WWW), (qq.v.).
Slightly larger than PCs, but considerably more powerful, workstations are used in such diverse tasks as designing machines, electronic circuits, and structures; creating advertisements, brochures, and magazines using DESKTOP PUBLISHING (q.v.) software; and training doctors in surgical techniques.
Now rivaling desktop computers in computer power, but considerably smaller in size, laptop and notebook computers have become a favorite tool of business people. Travelers carry these light, battery-powered computers into trains, planes, and hotel rooms to do their work much as if they were in the office. Through small modules called docking stations, these users can link their laptops to a variety of external services such as printers and communication networks.
“Embedded” computers are hidden in equipment. They perform such simple tasks as preventing a car’s brakes from locking or such complex ones as instructing a machine tool to perform a task or stabilizing a jumbo jet.
Today, the term computer is synonymous with digital computer, but until the 1960s, analog computers were popular. An analog computer relies on analogies between physical effects to make calculations. For example, the voltages in an analog computer may represent temperatures in a heat exchanger, capacitors may represent heat storage capacity, electrical currents may represent heat flow, and so forth. A digital computer, in contrast, deals with values as numerical digits. Because of their versatility, speed, and relatively low cost, digital computers have almost entirely replaced the analog variety.
Conversion between analog (continuously variable) signals and digital (discrete numerical value) signals is often necessary, however. In digital computer control of a chemical process such as pharmaceutical production, for example, the process variables are measured as analog signals representing pressure, temperature, and flow. They must be changed into digital signals by an ANALOG-TO-DIGITAL CONVERTER (q.v.) so that the computer can operate on them. Similarly, the digital signals that result from the computer operations must be changed into analog signals by a DIGITAL-TO-ANALOG CONVERTER (q.v.) to regulate pump speeds, heaters, coolers, and other control devices.
