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.

HISTORY

The first mechanical adding machine, a precursor of the digital computer, was devised in 1642 by the French philosopher and mathematician Blaise Pascal. This device employed a series of ten-toothed wheels, each tooth representing a digit from 0 to 9. The wheels were connected so that numbers could be added to each other by advancing the wheels by a correct number of teeth. In the 1670s the German philosopher and mathematician Gottfried Wilhelm von Leibniz improved on this machine by devising one that could also multiply.

The French inventor Joseph Marie Jacquard (1752–1834), in designing an automatic loom, used thin, perforated wooden boards to control the weaving of complicated designs. During the 1880s the American statistician Herman Hollerith (1860–1929) conceived the idea of using perforated cards, similar to Jacquard’s boards, for processing data. Employing a system that passed punched cards over electrical contacts, he was able to compile statistical information for the 1890 U.S. census.

The Analytical Engine.

Also in the 19th century, the British mathematician and inventor Charles Babbage worked out the principles of the modern digital computer. He conceived a number of machines, such as the Difference Engine, that were designed to handle complicated mathematical problems. Many historians consider Babbage and his associate, the British mathematician Augusta Ada Byron (Lady Lovelace, 1815–52), the daughter of the English poet Lord Byron, the true inventors of the modern digital computer. The technology of their time was not capable of translating their sound concepts into practice; but one of their inventions, the Analytical Engine, had many features of a modern computer. It had an input stream in the form of a deck of punched cards, a “store” for saving data, a “mill” for arithmetic operations, and a printer that made a permanent record.

Early Computers.

The building of analog computers began at the start of the 20th century. Early models calculated by means of rotating shafts and gears. Numerical approximations of equations too difficult to solve in any other way were evaluated with such machines. During both world wars, mechanical and, later, electrical analog computing systems were used as torpedo course predictors in submarines and as bombsight controllers in aircraft. Another system was designed to predict spring floods in the Mississippi River Basin.

In 1941 the German engineer Konrad Zuse (1910–95) built the Z3, the first fully functional digital computer to be program-controlled. (Zuse’s Plankalkül, written for the Z3, has been called the first programming language.) Also in the 1940s, Howard Aiken (1900–73), a Harvard University mathematician, created the Mark I, usually considered the first large-scale automatic digital computer. This machine, like the Z3, used relays; it was constructed from mechanical adding machine parts. The instruction sequence to be used to solve a problem was fed into the machine on a roll of punched paper tape, rather than being stored in the computer. In 1945, however, the idea of storing the program within the computer was set forth, based on the concepts of the Hungarian-American mathematician John von Neumann. The instructions would be stored within a so-called memory, freeing the computer from the speed limitations of the paper tape reader during execution and permitting problems to be solved without rewiring the computer.

Electronic Computers.

The rapidly advancing field of ELECTRONICS, (q.v.) led to construction of electronic digital computers. The British government built the so-called Colossus machines during World War II to break German codes, but they were special-purpose machines. The first large-scale general-purpose all-electronic computer was completed in 1946 at the University of Pennsylvania by the American engineer John Presper Eckert, Jr. (1919–95) and the American physicist John William Mauchly (1907–80). (Another American physicist, John Vincent Atanasoff, later successfully claimed that certain basic techniques he had developed were used in this computer.) Called ENIAC, for Electronic Numerical Integrator And Computer, the device contained 18,000 vacuum tubes and had a speed of several hundred multiplications per minute. Its program was wired into the processor and had to be manually altered.

The use of the TRANSISTOR, (q.v.) in computers in the late 1950s marked the advent of smaller, faster, and more versatile logical elements than were possible with vacuum-tube machines. The first commercial computer to use transistors was developed in 1957 by Seymour R. Cray, a pioneer in the design of supercomputers. Because transistors use much less power and have a much longer life, this development alone was responsible for the improved machines called second-generation computers. Components became smaller, as did intercomponent spacings, and the system became much less expensive to build.

Integrated Circuits.

In the late 1950s, the INTEGRATED CIRCUIT (q.v.), or IC, was introduced, making it possible for many transistors to be fabricated on one silicon substrate, or “chip,” with interconnecting wires plated in place. The IC resulted in a further reduction in price, size, and failure rate. The MICROPROCESSOR, (q.v.) became a reality in the mid-1970s with the introduction of the large scale IC (LSI) and, later, the very large scale IC (VLSI), with many thousands of interconnected transistors etched into a single silicon chip. Today, a single microprocessor chip may contain millions of transistors.

Computer Speed.

Everything that a digital computer does is based on one operation: the ability to determine if a switch, or “gate,” is open or closed. That is, the computer can recognize only two states in any of its microscopic circuits: on or off, high voltage or low voltage, or—in the case of numbers—0 or 1. The speed at which the computer performs this simple act, however, is what makes it a marvel of modern technology.

A key factor in a computer’s speed is its clock—a timing device that sends rapid pulses to the components to synchronize and pace them. The faster the clock, the more operations per second the computer will perform, all other things being equal.

Modern personal computers readily perform 500 million switching operations per second; such machines are said to have a speed of 500 megahertz (MHz), and the speed goes up with each new product introduction. At the other extreme, supercomputers, which handle vastly larger and more complex instructions, perform 10 billion or more operations per second (10 gigahertz, or GHz).

Digital computer speed and calculating power are further enhanced by the amount of data handled during each cycle. If a computer checks only one switch at a time, that switch can represent only two commands or numbers; thus ON would symbolize one operation or number, and OFF would symbolize another. By checking groups of switches linked as a unit, however, the computer increases the number of operations it can recognize at each cycle. For example, a computer that checks two switches at one time can represent four numbers (0 to 3) or can execute one of four instructions at each cycle, one for each of the following switch patterns: OFF-OFF (0); OFF-ON (1); ON-OFF (2); or ON-ON (3).

A variety of schemes are used to further boost computer speed. A cache memory is a small memory close to (or on) a microprocessor that stores recently used data on the valid premise that if the microprocessor has needed certain data recently, it is likely to need it again in the immediate future. Having the data nearby or actually on the microprocessor greatly reduces the time to access it.

Multiprocessing, or parallel processing, boosts speed by performing many operations simultaneously on two or more chips. As many as a thousand microprocessor chips work together in massively parallel processing. The software instructions that regulate the flow of data among the chips are complex indeed.

RISC (reduced instruction set computing) boosts speed by cutting the number of instructions for a computer to the bare minimum. With fewer instructions, the computer completes calculations faster, although programs tend to be longer than those for machines of the alternative type, called CISC (complex instruction set computers). CISC machines provide a large number of instructions, many of which may not be needed in the specific case.

Computers in the 1970s generally were able to check eight switches at a time. That is, they could check eight binary digits, or bits, of data, at every cycle. A group of 8 bits is called a byte, each byte containing 256 possible patterns of ONs and OFFs (or 1’s and 0’s). Each pattern is the equivalent of an instruction, a part of an instruction, or a particular type of datum, such as a number or a character or a graphics symbol. The pattern 11010010, for example, might be binary data—in this case, the decimal number 210 (see NUMBER SYSTEMS,)—or it might tell the computer to compare data stored in its switches to data stored in a certain memory-chip location.

The development of processors that can handle 16, 32, and 64 bits of data at a time has increased the speed of computers. The complete collection of recognizable patterns—the total list of operations—of which a computer is capable is called its instruction set. Both factors—number of bits at a time, and size of instruction sets—continue to increase with the ongoing development of modern digital computers.

HARDWARE

A digital computer is not actually a single machine, in the sense that most people think of computers. Instead it is a system composed of five distinct elements: (1) a central processing unit; (2) input devices; (3) memory storage devices; (4) output devices; and (5) a communications network, called a “bus,” that links all the elements of the system and connects the system to the external world.

Central Processing Unit (CPU).

The CPU may be a single chip (a microprocessor) or a series of chips that performs arithmetic and logical calculations and that times and controls the operations of the other elements of the system.

Most CPU chips and microprocessors are composed of four functional sections: (1) an arithmetic/logic unit; (2) registers; (3) a control section; and (4) an internal bus. The arithmetic/logic unit gives the chip its calculating ability and permits arithmetical and logical operations. The registers are temporary storage areas that hold data, keep track of instructions, and hold the location and results of these operations. The control section has three principal duties. It times and regulates the operations of the entire computer system; its instruction decoder reads the patterns of data in a designated register and translates the pattern into an activity, such as adding or comparing; and its interrupt unit indicates the order in which individual operations use the CPU, and regulates the amount of CPU time that each operation may consume.

The CPU’s internal bus is a network of communication lines that connects the internal elements of the processor and also leads to external connectors that link the processor to the other elements of the computer system. The three types of CPU buses are: (1) a control bus consisting of a line that senses input signals and another line that generates control signals from within the CPU; (2) the address bus, a one-way line from the processor that handles the location of data in memory addresses; and (3) the data bus, a two-way transfer line that both reads data from memory and writes new data into memory.

Input Devices.

These devices enable a computer user to enter data, commands, and programs into the CPU. The most common input device is the KEYBOARD, (q.v.). Information typed on the typewriter-like keyboard is translated by the computer into recognizable patterns. Almost as common is the “mouse,” a hand-guided pointing device that moves a pointer on a video display screen. Other input devices include light pens, which transfer graphics information from electronic pads into the computer; joysticks, which translate physical motion into motion on a display screen; light scanners, which “read” words or symbols on a printed page and “translate” them into electronic patterns that the computer can manipulate and store; and voice recognition modules, which take spoken words and translate them into digital signals for the computer to read. Storage devices can also be used to input data into the processing unit.

Storage Devices.

Computer systems can store data internally (in memory) and externally (on storage devices). Internally, temporary instructions or data can be stored in silicon RAM (Random-Access Memory) chips that are mounted directly on the computer’s main circuit board, or in chips mounted on peripheral cards that plug into the computer’s main circuit board. A RAM chip consists of switches that are sensitive to changes in electric current. So-called static RAM (SRAM) chips hold their bits of data as long as current flows through the circuit, whereas dynamic RAM (DRAM) chips need high or low voltages applied at regular intervals—every two milliseconds or so—if they are not to lose their information. SRAMs also access their data faster than DRAMs, although DRAM chips store more data.

Another type of internal memory consists of silicon chips on which all switches are already set. The patterns on these ROM (Read-Only Memory) chips form “firmware”—permanent commands, data, or programs that the computer needs to function correctly. RAM chips are like pieces of paper that can be written on, erased, and used again; ROM chips are like a book, with its words already set on each page. Both RAM and ROM chips are linked by circuitry to the CPU.

External storage devices, which may physically reside within the computer’s main processing unit, are external to the main circuit board. These devices store data as charges on a magnetically sensitive medium such as a disk coated with a fine layer of metallic particles. The most common external storage devices are so-called floppy and hard disks, although most large computer systems use magnetic tape storage units as well as hard disks. Floppy disks can easily be inserted and removed; they can contain from several hundred thousand bytes of data to well over a million bytes, depending on the system. Hard disks are permanently mounted in their cabinets, which contain the electronics to read data from and write data onto the magnetic disk surfaces. Hard disks can store up to several billion bytes. Using the same laser techniques that are used to create audio compact disks (CDs), CD-ROM technology offers large storage capacities. An ordinary CD-ROM can hold 650 megabytes (681,574,400 characters of information, because a megabyte is actually 1024 times 1024 bytes) of data. The entire text of this encyclopedia fills only about one-fourth of a single standard-size CD-ROM; the disk can therefore accommodate extensive digital graphics, video clips, and sound clips.

Output Devices.

These devices enable the user to see the results of the computer’s calculations or data manipulations. The most common output device is the video display terminal, a monitor that displays characters and graphics on a television-like screen. A video display terminal usually has a cathode-ray tube (CRT) like an ordinary television set, but small, portable computers use flat panel displays containing small cells that transmit or block light. Other standard output devices include printers and modems. A MODEM, (q.v.) links two or more computers by translating data signals for transmission over TELECOMMUNICATIONS, (q.v.) links.

Operating Systems.

Different types of peripheral devices—disk drives, printers, communications networks, and so on—handle and store data differently from the way the computer handles and stores it. Internal operating systems, usually stored in ROM, were developed primarily to coordinate and translate data flows from dissimilar sources, such as disk drives or co-processors (processing chips that perform simultaneous but different operations from the central processing unit). An operating system, often described as a “traffic cop,” is a master control program, stored in memory, that interprets user commands requesting various kinds of services, such as display, print, or copy a data file; list all files in a directory; or execute a particular program. The operating system then ensures that the commands are executed and regulates the flow of data and instructions.

Some operating systems were developed for specific products—VM/CMS for International Business Machines (IBM) mainframes, for example. Others were developed to meet specific needs, rather than for specific products, and have gained wide acceptance for that reason. American Telephone and Telegraph (AT&T) developed the UNIX operating system to help computers work together in a network and to establish “platform independence” (compatibility with all computer architectures); many other computer manufacturers have since adopted UNIX and workstations use it extensively.

Microsoft Corp. produced the Microsoft Disk Operating System (MS-DOS) for IBM PCs. As businesses and households enthusiastically adopted PCs, countless manufacturers of IBM “clones” adopted MS-DOS (see COMPUTER OPERATING SYSTEM,).

Software for windows is widely popular; such software treats the various programs in a computer as sheets of paper, or windows, that a user can overlap or overlay on the screen so that they can be worked on together. A windows environment also lets the user exchange information easily between programs—from a spreadsheet or graphics program to a word processing program, for example. Apple Computer, Inc., was the first to introduce windows in a commercially successful PC in 1984. This feature, together with a graphical user interface containing icons (screen images that the user clicks to open programs and execute commands), accounts for the famous “user-friendliness” of Apple’s Macintosh computers. In 1985, Microsoft introduced Microsoft Windows to enhance MS-DOS with the same intuitive graphical conveniences. Ten years later, Microsoft introduced a new operating system, Windows 95, which is even more convenient for users. It was followed by Windows 98.

PROGRAMMING

A program is a sequence of instructions that tells the hardware of a computer what operations to perform on data. Programs can be built into the hardware itself, or they may exist independently in a form known as software. In some specialized, or embedded, computers the operating instructions are contained in their circuitry; common examples are the microcomputers found in calculators, wristwatches, automobile engines, and microwave ovens. A general-purpose computer, on the other hand, contains some built-in programs (in ROM) or instructions (in the processor chip), but it depends on external programs to perform useful tasks. Once a computer has been programmed, it can do only as much or as little as the software controlling it at any given moment enables it to do. Software in widespread use includes a wide range of applications programs (instructions to the computer on how to perform various tasks).

Languages.

A computer must be given instructions in a “language” that it understands—that is, a particular pattern of binary digital information. On the earliest computers, programming was a difficult, laborious task, because vacuum-tube ON-OFF switches had to be set by hand. Teams of programmers often took days to program simple tasks such as sorting a list of names. Since that time a number of computer languages have been devised, some with particular kinds of functioning in mind and others aimed more at ease of use—the “user-friendly” approach.

Machine language.

Unfortunately, the computer’s own binary-based language, or machine language, is difficult for humans to use. The programmer must input every command and all data in binary form, and a basic operation such as comparing the contents of a register to the data in a memory-chip location might look like this: 11001010 00010111 11110101 00101011. Machine-language programming is such a tedious, time-consuming task that the time saved in running the program rarely justifies the days or weeks needed to write the program.

Assembly language.

One method programmers devised to shorten and simplify the process is called “assembly-language” programming. By assigning a short (usually three-letter) mnemonic code to each machine-language command, assembly-language programs could be written and “debugged”—cleaned of logic and data errors—in a fraction of the time needed by machine-language programmers. In assembly language, each mnemonic command and its symbolic operands equals one machine instruction. An “assembler” program translates the mnemonic “op-codes” (operation codes) and symbolic operands into binary language and executes the program. Assembly languages became known as second-generation languages, in contrast to the first-generation machine languages.

An assembly language, however, can be used only with one type of CPU chip or microprocessor. Programmers who expended much time and effort to learn how to program one computer had to learn a new programming style each time they worked on another machine. What was needed was a shorthand method by which one symbolic statement could represent a sequence of many machine-language instructions, and a method that would allow the same program to run on several types of machines. These needs led to the development of so-called high-level, or third-generation, languages.

High-level languages.

High-level languages often use words that are more like the English language—for example, LIST, PRINT, OPEN, and so on—as commands that might stand for a sequence of tens or hundreds of machine-language instructions. The commands are entered from the keyboard or from a program in memory or in a storage device, and they are intercepted by a program that translates them into machine-language instructions. The names fourth-generation and fifth-generation are sometimes given to languages that are even closer to natural languages or that rely on graphical development interfaces.

Translator programs are of two kinds: interpreters and compilers. With an interpreter, programs that “loop” back to re-execute part of their instructions reinterpret the same instruction each time it appears, so interpreted programs run much more slowly than machine-language programs. Compilers, by contrast, translate an entire program into machine language prior to execution, so such programs run nearly as rapidly as though they were written directly in machine language.

The first commercial programmer was probably computer scientist Grace Hopper, an American. After programming the Mark I, the experimental computer created by Aiken at Harvard, she worked on the UNIVAC I and II computers and developed a commercially usable high-level programming language called FLOW-MATIC. To facilitate computer use in scientific applications, IBM then developed a language that would simplify work involving complicated mathematical formulas. Begun in 1954 and completed in 1957, FORTRAN, (q.v.; FORmula TRANslation) was the first comprehensive high-level programming language that was widely used.

In 1957, the Association for Computing Machinery set out to develop a universal language that would correct some of FORTRAN’s perceived faults. A year later it released ALGOL (ALGOrithmic Language), another scientifically oriented language; widely used in Europe in the 1960s and ’70s, it has since been superseded by newer languages, while FORTRAN continues to be used because of the huge investment in existing programs. COBOL, (q.v.; COmmon Business Oriented Language), a commercial and business programming language, concentrated on data organization and file handling and was widely used at one time in business.

BASIC (Beginner’s All-purpose Symbolic Instruction Code) was developed at Dartmouth College in the early 1960s for use by nonprofessional computer users. The language came into almost universal use with the microcomputer explosion of the 1970s and ’80s. Condemned as slow, inefficient, and inelegant by its detractors, BASIC is nevertheless simple to learn and easy to use. Because many early microcomputers were sold with BASIC built into the hardware (in ROM memory) the language rapidly came into widespread use. As a very simple example of a BASIC program, consider the addition of the numbers 1 and 2, and the display of the result. This is written as follows (the numerals 10–40 are line numbers):

10 A = 1

20 B = 2

30 C = A + B

40 PRINT C

Although hundreds of different computer languages and variants exist, several others deserve mention. PASCAL, (q.v.), originally designed as a teaching tool, enjoyed considerable popularity for several years. LOGO was developed to introduce children to computers. C (see C AND C++,), a language Bell Laboratories computer scientist Dennis Ritchie (1941–    ) designed in the 1970s, is widely used in developing systems programs, such as language translators. LISP and Prolog (for “Programming in Logic”) have been used in research on ARTIFICIAL INTELLIGENCE (q.v.; AI).

A descendant of Pascal, the language Ada (named for Lady Lovelace; see History, above) was designed for military applications such as the Strategic Defense Initiative (“Star Wars”) missile program. Since then it has been adopted for such diverse uses as operating dialysis machines and controlling aircraft because of its real-time capability; that is, it responds almost instantaneously.

Different languages offer software writers different approaches, or “paradigms,” for the programming process. Perhaps best known is the “imperative,” or “procedural,” paradigm, which applies sequences of commands to manipulate data, commands that parallel the central processing unit’s basic cycle of fetch, interpret, and execute. The programmer develops the sequences of commands, or algorithms (see ALGORITHM,), needed to solve the problem at hand. Examples of imperative languages include FORTRAN, COBOL, ALGOL, BASIC, Pascal, Ada, and C. Prolog is an example of a “declarative” language; such languages typically offer massive libraries of problem-solving functions to the programmer, whose task becomes defining the problem precisely so the correct algorithm can be used. LISP belongs to the “functional” paradigm, which uses a modular approach; elements of a functional program are like “black boxes” (called functions), with the output of each one serving as the input into the next. A fourth paradigm is so-called object orientation.

Object-oriented languages.

C++ is a popular descendant of C that shares that language’s ability to adapt to a wide range of machines, from microprocessors to mainframes. In addition, it supports the object-oriented approach to programming; this approach makes use of objects, which are data structures that incorporate instructions (“methods”) that operate on the data. The methods are common to all objects that are instances of a particular “class,” which is a reusable module. Object-oriented languages are easy for programmers to use; instead of writing instructions for a task line by line, a programmer simply calls on an object to do the job. A later version of Ada (Ada 95) incorporates object-oriented concepts. Microsoft Corp.’s popular Visual Basic also makes some use of object orientation.

Another well-known object-oriented language is Java, which is derived from C++ and was developed in the early 1990s; it is used extensively for Internet and intranet applications. Java programs can be run on almost any kind of computer, if the computer is running software known as the Java Virtual Machine (JVM), which interprets the Java program for the computer. As long as a computer is running the JVM, a Java program is in theory not dependent on a specific piece of hardware.

Future Developments

Engineers continue to compress more circuit elements into smaller chip space. This not only makes computers more compact and less expensive, but it also allows them to operate faster, since signals are subjected to less delay in traveling between elements.

In the quest for speed, engineers are also chilling chips with liquid nitrogen. At the low temperature of liquid nitrogen (77K, or about –321 degrees Fahrenheit), chips run much faster; a microprocessor that runs at 100 MHz at room temperature can run at 250 MHz at 77K.

Engineers are also enthusiastic about experimental chips with switching devices made from superconducting materials. Such materials lose all their resistance when chilled, and can switch billions of times a second. New “high-temperature” superconductors, usually thin, copper-bearing ceramic films, need be chilled only to liquid nitrogen temperature—easier to attain than the 4.2K (about –452 degrees Fahrenheit) liquid-helium temperature previously required. See SUPERCONDUCTIVITY,.

In the more distant future lies the alluring prospect of quantum computers that would take advantage of the properties of QUANTUM THEORY, (q.v.) to perform calculations millions of times faster than the traditional computers of the late 1990s.

Meanwhile, multimedia desktop computers are on the verge of developing their full potential. Already equipped with CD-ROM players, multimedia PCs can tap a vast library of information, presented in both sound and video, on science, music, history, and art, for example. No longer limited to still or slow-moving displays, the newer machines can show action on the screen.

The growth of networking and the Internet will continue apace as computer users subscribe to services that provide information, access to “newsgroups,” and ELECTRONIC MAIL, (q.v.). Users can now set up voice conversations over the Internet. A limited form of video phone service is also available, and development is ongoing. Information “superhighways” are being built with optical fibers that transfer vast amounts of data between computers at breathtaking speeds. With this information transfer capacity, PC-based video phone service will become commonplace; people will confer with colleagues, viewing their live images on a screen shared with whatever text and graphics are needed for the discussion.

Further into the future, the elusive goal of artificial intelligence (AI) looms. AI means computers that learn, understand, recognize, and reason much as humans do. Although research on AI abounds, little in the way of solid results has been achieved except for expert systems, which are computers that have been provided with the knowledge and intuition of human experts in a given field. Expert systems advise technologists on such diverse tasks as troubleshooting communications networks, analyzing spectrograms, and diagnosing illness.        G.Ma., GARY MASTERS, M.A.; rev. by G.P.W., GEORGE PATRICK WATSON, Ph.D..

For further information on this topic, see the Bibliography, sections 3. Cybernetics, 541. Computer history, 542. Computer applications.