computer device capable of performing a series of arithmetic or logical operations. A computer is distinguished from a calculating machine, such as an electronic calculator , by being able to store a computer program (so that it can repeat its operations and make logical decisions), by the number and complexity of the operations it can perform, and by its ability to process, store, and retrieve data without human intervention. Computers developed along two separate engineering paths, producing two distinct types of computer—analog and digital. An analog computer operates on continuously varying data; a digital computer performs operations on discrete data.

Computers are categorized by both size and the number of people who can use them concurrently. Supercomputers are sophisticated machines designed to perform complex calculations at maximum speed; they are used to model very large dynamic systems, such as weather patterns. Mainframes, the largest and most powerful general-purpose systems, are designed to meet the computing needs of a large organization by serving hundreds of computer terminals at the same time. Minicomputers, though somewhat smaller, also are multiuser computers, intended to meet the needs of a small company by serving up to a hundred terminals. Microcomputers, computers powered by a microprocessor , are subdivided into personal computers and workstations, the latter typically incorporating RISC processors . Although microcomputers were originally single-user computers, the distinction between them and minicomputers has blurred as microprocessors have become more powerful. Linking multiple microcomputers together through a local area network or by joining multiple microprocessors together in a parallel-processing system has enabled smaller systems to perform tasks once reserved for mainframes, and the techniques of grid computing have enabled computer scientists to utilize the unemployed processing power of connected computers.

Advances in the technology of integrated circuits have spurred the development of smaller and more powerful general-purpose digital computers. Not only has this reduced the size of the large, multi-user mainframe computers—which in their early years were large enough to walk through—to that of large pieces of furniture, but it has also made possible powerful, single-user personal computers and workstations that can sit on a desktop. These, because of their relatively low cost and versatility, have largely replaced typewriters in the workplace and rendered the analog computer inefficient.

Analog Computers

An analog computer represents data as physical quantities and operates on the data by manipulating the quantities. It is designed to process data in which the variable quantities vary continuously (see analog circuit ); it translates the relationships between the variables of a problem into analogous relationships between electrical quantities, such as current and voltage, and solves the original problem by solving the equivalent problem, or analog, that is set up in its electrical circuits. Because of this feature, analog computers were especially useful in the simulation and evaluation of dynamic situations, such as the flight of a space capsule or the changing weather patterns over a certain area. The key component of the analog computer is the operational amplifier , and the computer's capacity is determined by the number of amplifiers it contains (often over 100). Although analog computers are commonly found in such forms as speedometers and watt-hour meters, they largely have been made obsolete for general-purpose mathematical computations and data storage by digital computers.

Digital Computers

A digital computer is designed to process data in numerical form (see digital circuit ); its circuits perform directly the mathematical operations of addition, subtraction, multiplication, and division. The numbers operated on by a digital computer are expressed in the binary system ; binary digits, or bits, are 0 and 1, so that 0, 1, 10, 11, 100, 101, etc., correspond to 0, 1, 2, 3, 4, 5, etc. Binary digits are easily expressed in the computer circuitry by the presence (1) or absence (0) of a current or voltage. A series of eight consecutive bits is called a "byte" ; the eight-bit byte permits 256 different "on-off" combinations. Each byte can thus represent one of up to 256 alphanumeric characters, and such an arrangement is called a "single-byte character set" (SBCS); the de facto standard for this representation is the extended ASCII character set. Some languages, such as Japanese, Chinese, and Korean, require more than 256 unique symbols. The use of two bytes, or 16 bits, for each symbol, however, permits the representation of up to 65,536 characters or ideographs. Such an arrangement is called a "double-byte character set" (DBCS); Unicode is the international standard for such a character set. One or more bytes, depending on the computer's architecture, is sometimes called a digital word; it may specify not only the magnitude of the number in question, but also its sign (positive or negative), and may also contain redundant bits that allow automatic detection, and in some cases correction, of certain errors (see code ; information theory ). A digital computer can store the results of its calculations for later use, can compare results with other data, and on the basis of such comparisons can change the series of operations it performs. Digital computers are used for reservations systems, scientific investigation, data-processing and word-processing applications, desktop publishing , electronic games , and many other purposes.

Processing of Data

The operations of a digital computer are carried out by logic circuits , which are digital circuits whose single output is determined by the conditions of the inputs, usually two or more. The various circuits processing data in the computer's interior must operate in a highly synchronized manner; this is accomplished by controlling them with a very stable oscillator , which acts as the computer's "clock." Typical computer clock rates range from several million cycles per second to several hundred million, with some of the fastest computers having clock rates of about a billion cycles per second. Operating at these speeds, digital computer circuits are capable of performing thousands to trillions of arithmetic or logic operations per second, thus permitting the rapid solution of problems that would be impossible for a human to solve by hand. In addition to the arithmetic and logic circuitry and a small number of registers (storage locations that can be accessed faster than main storage and are used to hold the intermediate results of calculations), the heart of the computer—called the central processing unit, or CPU—contains the circuitry that decodes the set of instructions, or program, and causes it to be executed.

Storage and Retrieval of Data

Associated with the central processing unit is the storage unit, or memory, where results or other data are stored for periods of time ranging from a small fraction of a second to days or weeks before being retrieved for further processing. Once made up of vacuum tubes and later of small doughnut-shaped ferromagnetic cores strung on a wire matrix, main storage now consists of integrated circuits , each of which contains thousands of semiconductor devices. Where each vacuum tube or core represented one bit and the total memory of the computer was measured in thousands of bytes (or kilobytes, KB), each semiconductor device now represents millions of bytes (or megabytes, MB) and the total memory of mainframe computers is measured in billions of bytes (or gigabytes, GB). Random-access memory (RAM), which both can be read from and written to, is lost each time the computer is turned off. Read-only memory (ROM), which cannot be written to, maintains its content at all times and is used to store the computer's control information.

Programs and data that are not currently being used in main storage can be saved on auxiliary storage, or external storage. Although punched paper tape and punched cards once served this purpose, the major materials used today are magnetic tape and magnetic disks, which can be read from and written to, and two types of optical disks , the compact disc (CD) and its successor the digital versatile disc (DVD). DVD is an improved optical storage technology capable of storing vastly greater amounts of data than the CD technology. CD–Read-Only Memory (CD-ROM) and DVD–Read-Only Memory (DVD-ROM) disks can only be read—the disks are impressed with data at the factory but once written cannot be erased and rewritten with new data. The latter part of the 1990s saw the introduction of new optical storage technologies: CD-Recordable (CD-R) and DVD-Recordable (DVD-R), optical disks that can be written to by the computer to create a CD-ROM or DVD-ROM, but can be written to only once; and CD-ReWritable (CD-RW), DVD-ReWritable (DVD-RW and DVD+RW), and DVD–Random Access Memory (DVD-RAM), disks that can be written to multiple times.

When compared to semiconductor memory, magnetic and optical storage is less expensive, is not volatile (i.e., data is not lost when the power to the computer is shut off), and provides a convenient way to transfer data from one computer to another. Thus operating instructions or data output from one computer can be stored away from the computer and then retrieved either by the same computer or another. In a system using magnetic tape the information is stored by a specially designed tape recorder somewhat similar to one used for recording sound. In magnetic and optical disk systems the principle is the same except that the magnetic or optical medium lies in a path, or track, on the surface of a disk. The disk drive also contains a motor to spin the disk and a magnetic or optical head or heads to read and write the data to the disk. Drives take several forms, the most significant difference being whether the disk can be removed from the drive assembly.

Removable magnetic disks are most commonly made of mylar enclosed in a paper or plastic holder. These floppy disks have varying capacities, with very high density disks holding 250 MB—more than enough to contain a dozen books the size of Tolstoy's Anna Karenina. Compact discs can hold many hundreds of megabytes, and are used, for example, to store the information contained in an entire multivolume encyclopedia or set of reference works, and DVD disks can hold ten times as much as that. Nonremovable disks are made of metal and arranged in spaced layers. They can hold more data and can read and write data much faster than floppies.

Data are entered into the computer and the processed data made available via input/output devices. All auxiliary storage devices are used as input/output devices. For many years, the most popular input/output medium was the punched card. Although this is still used, the most popular input device is now the computer terminal and the most popular output device is the high-speed printer . Human beings can directly communicate with the computer through computer terminals, entering instructions and data by means of keyboards much like the ones on typewriters, by using a pointing device such as a mouse, trackball, or touchpad, or by speaking into a microphone that is connected to computer running voice-recognition software. Responses may be displayed on a cathode-ray tube , liquid-crystal display, or printer. The CPU, main storage, auxiliary storage, and input/output devices collectively make up a system.

Sharing the Computer's Resources

Generally, the slowest operations that a computer must perform are those of transferring data, particularly when data is received from or delivered to a human being. The computer's central processor is idle for much of this period, and so two similar techniques are used to use its power more fully.

Time sharing, used on large computers, allows several users at different terminals to use a single computer at the same time. The computer performs part of a task for one user, then suspends that task to do part of another for another user, and so on. Each user only has the computer's use for a fraction of the time, but the task switching is so rapid that most users are not aware of it. Most of the tens of millions of computers in the world are stand-alone, single-user devices known variously as personal computers or workstations. For them, multitasking involves the same type of switching, but for a single user. This permits a user, for example, to have one file printed and another sorted while editing a third in a word-processing session. Such personal computers can also be linked together in a network, where each computer is connected to others, usually by wires or coaxial cables, permitting all to share resources such as printers, modems , and hard-disk storage devices.

Computer Programs and Programming Languages

Before a computer can be used to solve a given problem, it must first be programmed, that is, prepared for solving the problem by being given a set of instructions, or program. The various programs by which a computer controls aspects of its operations, such as those for translating data from one form to another, are known as software, as contrasted with hardware, which is the physical equipment comprising the installation. In most computers the moment-to-moment control of the machine resides in a special software program called an operating system, or supervisor. Other forms of software include assemblers and compilers for programming languages and applications for business and home use (see computer program ). Software is of great importance; the usefulness of a highly sophisticated array of hardware can be severely compromised by the lack of adequate software.

Each instruction in the program may be a simple, single step, telling the computer to perform some arithmetic operation, to read the data from some given location in the memory, to compare two numbers, or to take some other action. The program is entered into the computer's memory exactly as if it were data, and on activation, the machine is directed to treat this material in the memory as instructions. Other data may then be read in and the computer can carry out the program to solve the particular problem.

Since computers are designed to operate with binary numbers, all data and instructions must be represented in this form; the machine language, in which the computer operates internally, consists of the various binary codes that define instructions together with the formats in which the instructions are written. Since it is time-consuming and tedious for a programmer to work in actual machine language, a programming language , or high-level language, designed for the programmer's convenience, is used for the writing of most programs. The computer is programmed to translate this high-level language into machine language and then solve the original problem for which the program was written. Certain high-level programming languages are universal, varying little from machine to machine.

Development of Computers

Although the development of digital computers is rooted in the abacus and early mechanical calculating devices, Charles Babbage is credited with the design of the first modern computer, the "analytical engine," during the 1830s. American scientist Vannevar Bush built a mechanically operated device, called a differential analyzer, in 1930; it was the first general-purpose analog computer. John Atanassoff constructed the first semielectronic digital computing device in 1939.

The first fully automatic calculator was the Mark I, or Automatic Sequence Controlled Calculator, begun in 1939 at Harvard by Howard Aiken, while the first all-purpose electronic digital computer, ENIAC (Electronic Numerical Integrator And Calculator), which used thousands of vacuum tubes, was completed in 1946 at the Univ. of Pennsylvania. UNIVAC (UNIVersal Automatic Computer) became (1951) the first computer to handle both numeric and alphabetic data with equal facility; this was the first commercially available computer.

First-generation computers were supplanted by the transistorized computers (see transistor ) of the late 1950s and early 60s, second-generation machines that were smaller, used less power, and could perform a million operations per second. They, in turn, were replaced by the third-generation integrated-circuit machines of the mid-1960s and 1970s that were even smaller and were far more reliable. The 1980s and 90s were characterized by the development of the microprocessor and the evolution of increasingly smaller but powerful computers, such as the personal computer and personal digital assistant , which ushered in a period of rapid growth in the computer industry.

Bibliography

See S. G. Nash, A History of Scientific Computing (1990); D. I. A. Cohen, Introduction to Computer Theory (2d ed. 1996); P. Norton, Peter Norton's Introduction to Computers (2d ed. 1996); A. W. Biermann, Great Ideas in Computer Science: A Gentle Introduction (2d ed. 1997); R. L. Oakman, The Computer Triangle: Hardware, Software, People (2d ed. 1997); R. Maran, Computers Simplified (4th ed. 1998); A. S. Tanenbaum and J. R. Goodman. Structured Computer Organization (4th ed. 1998).

COMPUTING The use of an electronic device that accepts data, performs mathematical and logical operations at speed on those data, and displays the results. Computers, although initially developed as calculating devices and open to a range of uses, have become central to communicative technology, and relate to language in at least three ways: (1) They require their own artificial languages in order to function. (2) Their use has adapted natural language to new ends, such as the processing of texts by computer. (3) Their users have developed their own styles and registers for working with them and talking about them. Since the 1950s, these factors have developed explosively and are major influences on late 20c English, the language most closely involved in computing.

Nature

The present-day computer derives from British work during the Second World War on cryptographic machines and is the most recent in a line of calculating devices that includes the abacus, the Jacquard loom, Babbage's Analytical Engine, and Hollerith's tab-sorter. Its primary purpose has been to compute, not to compile or converse. There are two kinds of computer: analog and digital. Analog computers, which are related to the slide rule and tables of logarithms (and virtually obsolete), use the strengths of voltages to represent the size of numbers, whereas digital computers use electrical signals only in the on/off form. Currently, digital computers consist of four major parts: (1) A processor or central processing unit (CPU), which executes commands, performing arithmetical, logical, and manipulative operations on the data stored in the second part. (2) A memory, the information store. Most computers have at least two kinds of memory: primary and secondary. Primary memory is usually silicon chips, typically DRAM (dynamic random access memory) chips. ‘Random access’ means that any part may be obtained immediately, as with a book that can be opened to any page. The process is fast, usually less than one microsecond to obtain an item of information. Secondary memory is usually magnetic disk, made of one or more platters rotating under a reading head. It is not random access: a particular part of the disk cannot be read until it rotates under the reading head, which usually takes several milliseconds. Storage is measured in bytes, one byte containing eight bits, and representing storage for one character in European alphabets. See ASCII. (3) Input/output equipment, which enables the user to get information into and out of the machine. The information is entered most commonly through a keyboard but also through removable disks, tapes, and other devices. Output goes to display screens, to printers (which produce text etc., usually known as hard copy), and also to disks and tapes. (4) Communications equipment, which permits a computer to ‘talk’ to other machines and to people located at a distance from it. The equipment includes a modem (an acronym for ‘modulator demodulators’), which connect computers by telephone line, and networks to let machines talk at high speed to each other, as for example in using the INTERNET and the WORLD-WIDE WEB.

Computer programs

Since computers work very fast, they cannot be directed step by step. Instead, a script must first be written for the computer to follow. The script typically contains sequences to be repeated, so that the script is much shorter than the operation as executed. The computer responds to machine language, which is binary code (strings of 0s and 1s), in which the operations are very simple (such as elementary arithmetic or moving one piece of data from one place to another). Such scripts are written in higher-level languages called computer programs (BrE following AmE in this spelling, but AmE follows BrE in doubling the m in programming). A distinction is now universally made between the equipment as hardware and software, the latter now generally made available as commercial software packages.

Computer languages

Also programming languages, high-level languages. Digital computers can follow directions written in a great variety of artificial languages that provide precise specifications of operations to be done and the order in which they must be done. Although strings of letters are used to name commands in these languages, they are quite different from natural language. Among other things, they must be logical and unambiguous: unlike people, computers do not know that the and in I like bread and jam means ‘both together’, while the and in I like cats and dogs does not imply that both must be present at once (= ‘I like cats and I like dogs’). Compared with natural language, high-level computer languages normally have: (1) Very short words: most programmers save effort by giving variables names such as x, one or two letters long, and by using many abbreviations, such as del for delete. (2) Very short utterances: written English sentences might average 20 words in length, but statements in programming language are typically only six items long. (3) Little syntactic variety: the typical computer language at present has a grammar of about 100 rules, compared with thousands in a formal grammatical description of English.

Specific languages

The many programming languages are divided into business languages (verbose, emphasizing simple operations on complex data) and scientific languages (terse, emphasizing complex operations on simple data). They often have distinctive histories and functions, and names of etymological interest. ALGOL, a language suitable for expressing algorithms, is the computational equivalent of Esperanto, created in 1960 by an international committee. Its name, a reduction of Algorithm Language, is a homonym of the star Algol (Arabic, ‘the ghoul’). BASIC is short for Beginner's All-Purpose Symbolic Instruction Code, designed at Dartmouth College in New Hampshire in 1965 by J. Kemeny and T. Kurtz. It is often the first programming language learned and is similar to the Basic of BASIC ENGLISH, also an acronym. ADA was designed in a competition run by the US Department of Defense from 1974 to 1980, going through successive refinements with such names as Strawman, Woodenman, Tinman, Ironman. The French computer scientist Jean Ichbiah led the winning team. It was named after Lady Ada Lovelace, daughter of the poet Byron and a supporter of Charles Babbage, the inventor of the Analytical Engine, an early mechanical digital computer. She is often called the first programmer. For some years, the goal of ‘programming in English’ (that is, using a more or less unrestricted subset of the natural language) attracted attention, but it has so far proved unattainable.

Processing text

Computers, among other things, are extensions of writing and print systems, and have therefore been used with greater or less success to do such things as evaluate, index, parse, translate, correct, and ‘understand’ text. When a suitably programmed computer is fed English, it can process it at several levels, but with decreasing competence as the task becomes more complex. The following sequence is typical:

1. The character level.

Text can be entered into a computer by three means: keying it, typically into a word processor which will format the text (arranging the line lengths and character positions); scanning it, using a machine which transfers a paper version into an image followed by a program that seeks to recognize the characters in it; transferring it electronically, typically by diskette or telephone, from another compatible computer. Transfer is the fastest and most accurate method, but currently the least used. When a cleanly typed or printed original is available, without too many fonts or typographic complexities, scanning is faster and easier than rekeying. Once the text is entered, computers can print it in a wide variety of typefaces, sizes, and page formats, using either a printer or a desktop publishing system.

2. The word level.

A spelling checker can find some kinds of typing mistakes, usually by comparing words with a dictionary list and noting those that are not in that list. Programs can make word lists and concordances (lists of each word with some context before and after it). By noting the most frequent words in a document, and comparing the word frequencies in a particular text with the average word frequencies in English, a program can suggest words that might be used for indexing the document. The counting of relative word frequencies and comparison with word frequencies from a standard sample can also help in guessing the authorship of anonymous works or measuring the readability level of a text.

3. The sentence level.

On the level of syntax, PARSING programs can try to define the structure of sentences and relationships among words. This is typically done by applying grammar rules of the form ‘a verb phrase may be a verb followed by an adverb’. Unfortunately many sentences are ambiguous. In the preceding sentence, a computer would not know whether Unfortunately modified the verb (implying that it is sad that ambiguous sentences occur) or the adjective many (suggesting disappointment that ambiguous sentences are so frequent). Adding a comma after Unfortunately could, however, serve as a means of disambiguation. However, some kinds of grammatical and stylistic errors can be diagnosed, and grammar checkers and style checkers have become available to help in the writing of business letters and the propagation of PLAIN ENGLISH.

4. The message level.

At the level of word-and-sentence meaning, semantic analysis can map a sentence into a knowledge-presentation language. Some research projects have been able to take such sentences as Which ships are in port? and answer them by looking at a table of ship locations, but such systems currently operate in strictly limited subject areas. Other applications of semantics include machine translation and direct generation of language by computers (that is, the computer produces text without human input).

The above levels of activity depend on computational linguists writing rules of analysis, accumulating a GRAMMAR of syntactic and/or semantic rules for such a language as English. An alternative strategy for processing written language, however, uses reference books: the use of a MACHINE-READABLE dictionary or thesaurus may help a computer make reasonable guesses about which sense of an ambiguous word is intended in a particular context. Another strategy relies on the statistical properties of large corpora to determine word relationships. Such methods have allowed parsing without writing a grammar in advance, a higher quality of error correction in spelling, and the automatic recognition of phrases. However, they handle uncommon constructions less well than the grammar-based procedures handle them, and depend for their success on the fact that such constructions are uncommon. See COMPUTERESE, COMPUTER USAGE, CONCORDANCE, CORPUS, EMOTICON, ICON.

COMPUTERS: MACHINES OF THE DECADE

You Say You Want a Revolution

By the middle 1980s the social revolution envisioned twenty years earlier by the pioneers of the small computer was in full swing. In 1981 some 750,000 personal computers were estimated to be in use in American homes; 39.4 million computers were shipped between 1984 and 1988. In 1984 alone Americans bought $37.6 million worth of computer software for home use, about two-thirds of it in the "entertainment" category—that is, computer games. By the end of 1982, 250 different computer games were available, and some $2 billion worth were sold. In the mid 1980s home computers came in three types. For less than $100, one could buy a game-only computer made by Atari or Sega. It hooked up to the family television set, which acted as the monitor, and the programs came as plug-in cartridges or tape cassettes similar to those used in tape recorders. For less than $500, the home user could buy a computer that purported to serve the serious user—a Timex Sinclair 1000, a Commodore VIC-20, or an Atari 400—but these machines were normally upgraded game computers with simple programs. For $1,000 to $2,000, the more serious home user could buy an Apple II, an IBM Personal Computer, or a Radio Shack TRS-80 with a keyboard, a monitor, and as much as thirty-two kilobytes of RAM (random-access memory). For another $750 or so a printer could be attached, making the computer useful as a word processor. Those adventuresome computer users who were willing to spend $100 for a telephone modem were the trail-blazers. They could connect with bulletin board services (BBSs) and acquire information—or, more usually, exchange ideas with other computer users. The BBSs were free (except for the cost of a long-distance call, if the BBS was in a different area) and often allowed pseudonymous subscriptions. Commercial services, such as CompuServe and The Source, charged a monthly fee for a certain number of hours of use and certain services; additional time on-line or more specialized services carried extra charges. In 1981 180,000 modems were in American homes; by 1988 there were 10.9 million.

Machine of the Year

On 3 January 1983 a computer appeared on the cover of Time as the Machine of the Year. The magazine was saluting the personal computer's potential rather than its accomplishments. Clearly, the vision of the "cyberpunks" of the late 1960s and early 1970s had captured the attention, if not the imagination, of the average American. The challenge was to find uses for the computer that took advantage of the machines' unique capabilities and could not be accomplished more efficiently by traditional means (such as the typewriter or calculator). As adults struggled to justify their purchase of the devices, their children played computer games and came to regard computing as a routine part of life. Through such popular game programs as Pac-Man and Super Mario Brothers, children developed an interest in computer hardware and in the programming routines that told the computer what to do. Bit, byte, RAM, ROM (read-only memory), CPU (central processing unit), and software were standard words in the vocabulary of elementary-school children that baffled their elders.

Uses

Meanwhile, the older set sought a practical use for computing. The typewriter industry was the first to feel the impact as word-processing programs offered erratic typists an efficient way to correct mistakes. For home finances and record keeping there was VisiCalc, an early spreadsheet program that allowed nearly instant calculation according to formulas determined by the user. Software manufacturers struggled, with mixed success, to provide other practical uses for home computers. Thousands of programs were introduced each year in the mid 1980s, most of uncertain utility. The determined user could store recipes, inventory household items, learn languages, and fill in the blanks on prepared legal forms, such as simple wills and bills of sale, using computer programs, though often it was more efficient to accomplish these tasks using traditional means. The uses that established the computer among middle-class families as a required household item were basic ones—writing, ciphering, and placating the children, who amused themselves for hours on end with digital games.

Incompatibility

A serious drawback to the computers of the early 1980s was that different brands, or even different models produced by the same company, were often incompatible. Because there was no clear standard of operating software, ambitious computer companies, notably Sharp, marketed computers that would only run software provided by the manufacturer. Thus, if one bought a Sharp computer, one had to buy programs from Sharp, as well—a situation that frustrated experienced users, who may, for example, have had one type of computer at home and another at the office. Software incompatibility also served to add to the confusion of novices, who failed to understand the nuances of hardware architecture. As Microsoft Corporations's MS-DOS and Apple's Macintosh became established as the two major operating systems, customers and software producers insisted that computers be able to run any software written for one or the other. General users were attracted to later-generation machines and software that required only simple typing skills and intuitive responses to "icons"—pictures on the monitor screen that represented sets of complicated instructions to the machine; the instructions could be executed by using a mouse (a small device that sat on the desktop next to the keyboard) to position a cursor (pointer) over the icon and clicking a button. By the end of the 1980s the term user friendly had become not only a merchandising slogan but also a basic principle of computer hardware and software design.

Source:

Otto Friedrich, "Machine of the Year: The Computer Moves In," Time (3 January 1983): 14-24.

computer Device that processes data (information) by following a set of instructions called a program. All digital computers work by manipulating data represented as numbers. The tallying principle of the abacus was mechanized in calculating machines, such as those devised by Charles Babbage, in which complicated calculations were processed by means of geared wheels. By the mid-1940s mechanical machines were replaced by electronic versions. Some used groups of electromagnetic switches, called relays, to register binary numbers. At any instant, each switch could be either on or off, corresponding to the digits 1 or 0 in the binary system. Stages in the long-term development of electronic digital computers are termed computer generations. In 1946, engineers at the University of Pennsylvania developed the first generation computer. The 27-tonne machine called ENIAC (Electronic Numerical Indicator and Computer) used electronic valves instead of relays. Programming ENIAC to do a particular task was a lengthy process that consisted of changing wired connections. John Von Neumann helped to develop techniques for storing programs in code to avoid this problem. In 1951, UNIVAC 1 became the first computer offered for general sale. This second generation computer used a transistor to perform the same role as valves. As a result, computers became smaller and more commonplace. In the 1960s, a third generation of computers appeared with the invention of integrated circuits, leading to a further reduction in size. Fourth generation computers, developed in the 1980s, are even smaller, utilizing powerful microprocessors. Microprocessors contain a complete central processing unit (CPU) which controls operations. The latest microprocessors contain more than a million transistors and other components, all in a package little bigger than a postage stamp. Read-Only Memory (ROM) and Random Access Memory (RAM) chips act as permanent and temporary electronic memories for storing data. A typical desktop computer system consists of: a main unit, containing a central processor together with memory chips and storage devices (usually magnetic disks); a monitor, containing a cathode-ray tube; a keyboard; a mouse and printer. Computer programs are usually stored on disks and transferred to the machine's RAM when required. The keyboard and mouse are called input devices, since they allow the user to feed information into the computer. The keyboard enables the user to enter letters, numbers and other symbols. The mouse, a graphical user interface (GUI), is a small device moved by hand, which enables the user to control the computer by positioning a pointer on the monitor screen, to select functions from a list. Fifth generation computers using very large-scale integration (VLSI) chips will utilize the developments of artificial intelligence (AI) and may be controlled by spoken commands. A magnetic disk drive, such as a hard disk, acts as both an input and output device. It can supply programs and data to the computer, and store its output. Most computers have CD-ROM drives; these receive data from an optical storage disk. Many other peripherals are used, such as a scanner which converts images into a digital signal so that they can be stored and displayed by the computer, and other hardware for storing and manipulating sounds. The modern computer market is dominated by PCs – the generic term used to refer to machines based on the original IBM personal computer produced in the early 1980s. All these machines use an operating system (such as DOS or Windows) produced by the giant software corporation, Microsoft. Other popular operating systems include Apple Macintosh and UNIX.

computer A device or system that is capable of carrying out a sequence of operations in a distinctly and explicitly defined manner. The operations are frequently numerical computations or data manipulations but also include input/output; the operations within the sequence may depend on particular data values. The definition of the sequence is called the program. A computer can have either a stored program or wired program. A stored program may exist in an alterable (read-write or RAM) memory or in a nonalterable (ROM) memory. See also digital computer, analog computer, von Neumann machine.

com·put·er / kəmˈpyoōtər/ • n. an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program. ∎  a person who makes calculations, esp. with a calculating machine.

Computer

See Information Technology

computer •exploiter, goitre (US goiter), loiter, reconnoitre (US reconnoiter), Reuter •anointer, appointer, jointer, pointer •cloister, hoister, oyster, roister •accoutre (US accouter), commuter, computer, disputer, hooter, looter, neuter, pewter, polluter, recruiter, refuter, rooter, saluter, scooter, shooter, souter, suitor, tooter, transmuter, tutor, uprooter •booster, rooster •doomster • freebooter • sharpshooter •peashooter • six-shooter •troubleshooter • prosecutor •persecutor • prostitutor •telecommuter •footer, putter •Gupta • Worcester • Münster •pussyfooter • executor •contributor, distributor •collocutor, interlocutor •abutter, aflutter, butter, Calcutta, clutter, constructor, cutter, flutter, gutter, mutter, nutter, scutter, shutter, splutter, sputter, strutter, stutter, utter •abductor, conductor, destructor, instructor, obstructor •insulter •Arunta, Bunter, chunter, Grantha, grunter, Gunter, hunter, junta, punter, shunter •corrupter, disrupter, interrupter •sculptor •adjuster, Augusta, bluster, buster, cluster, Custer, duster, fluster, lustre (US luster), muster, thruster, truster •huckster • Ulster • dumpster •funster, Munster, punster •funkster, youngster •gangbuster • filibuster • blockbuster •semiconductor • headhunter •woodcutter •lacklustre (US lackluster)