Computers, Devices For Processing, Storing And Displaying Information.
Computer once meant a person who did calculations, but now the term almost universally refers to automated electronic machinery. The first section of this article focuses on modern digital electronic computers and their design, component parts, and applications. The second section covers the history of computing. See Computer Science for details on computer architecture, software, and theory.
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Computing Basics
Earlier computers were mainly used for numerical calculations. However, as any information could be encoded numerically, people soon realized that computers were capable of general-purpose information processing. Their ability to handle large amounts of data has increased the range and accuracy of weather forecasting. Their speed has allowed them to make decisions about routing telephone connections through a network, and to control mechanical systems such as automobiles, nuclear reactors and robotic surgical equipment. They’re also cheap enough that they can be embedded in everyday appliances and “smart” into clothes dryers and rice cookers. Computers have allowed us to ask and answer questions that previously could not be pursued. These questions can be about the DNA sequence in genes, patterns of activity in the consumer market, or all uses of a word in text stored in a database. Increasingly, computers can also learn and adapt as they operate.
Computers also have limitations, some of which are theoretical. For example, there are undecidable propositions whose truth cannot be determined within a given set of rules, such as the logical structure of a computer. Because no universal algorithmic method can exist for identifying such propositions, the asked computer will continue indefinitely to obtain the truth of such a proposition—a condition known as the “halting problem”. Is known. (See Turing machines.) Other limitations reflect current technology. Human brains are skilled at recognizing spatial patterns – for example, easily distinguishing human faces – but this is a daunting task for computers, which must process information sequentially rather than deciphering overall details at a glance. . Another problematic area for computers involves natural language interactions. Because so much common sense and contextual information is assumed in normal human communication, researchers have yet to address the problem of providing relevant information for general-purpose natural language programs.
Technicians operate the systems console on the new UNIVAC 1100/83 computer at the Fleet Analysis Center, Corona Annex, Naval Weapons Station, Seal Beach, CA. June 1, 1981. Univac magnetic tape driver or reader in the background. universal automatic computer
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Analog Computer
Analog computers use a constant physical magnitude to represent quantitative information. At first they represented quantities with mechanical components (see Differential Analyzers and Integrators), but after World War II voltages were used; By the 1960s, digital computers had largely replaced them. Nevertheless, analog computers, and some hybrid digital-analog systems, continued in use through the 1960s in tasks such as aircraft and spaceflight simulation.
One advantage of analog computation is that it can be relatively simple to design and build an analog computer to solve a single problem. Another advantage is that analog computers can often represent and solve a problem in “real time”; That is, the computation proceeds at the same rate as the system being modeled by it. Their main disadvantages are that analog representations are limited in precision – usually a few decimal places but less in complex systems – and general-purpose devices are expensive and not easily programmed.
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Digital Computer
Unlike analog computers, digital computers represent information in discrete form, usually as a sequence of 0s and 1s (binary digits, or bits). The modern era of digital computers began in the United States, Britain, and Germany in the late 1930s and early 1940s. The first devices to use a switch operated by an electromagnet (relay). Their programs were stored on punched paper tapes or cards, and they had limited internal data storage. For historical developments, see the Invention of the modern computer section.
Mainframe Computer
During the 1950s and ’60s, Unisys (makers of the UNIVAC computers), International Business Machines Corporation (IBM) and other companies built large, expensive computers of increasing power. They are used by major corporations and government research laboratories.
rly IBM machines were almost always leased rather than sold), and in 1964 the largest IBM S/360 computer cost several million dollars.
These computers came to be called mainframes, although the term did not become common until smaller computers were created. Mainframe computers were characterized (for their time) by large storage capacities, fast components, and powerful computational capabilities. They were highly reliable, and, because they often met critical needs in an organization, they were sometimes designed with redundant components that allowed them to survive partial failures. Because they were complex systems, they were operated by a staff of systems programmers, who alone had access to the computer. Other users submitted “batch jobs” to be run one by one on the mainframe.
Such systems are still important today, although they are no longer the only, or even the primary, central computing resource of an organization, which would typically contain hundreds or thousands of personal computers (PCs). Mainframes now provide high-capacity data storage for Internet servers, or, through time-sharing techniques, they allow hundreds or thousands of users to run programs simultaneously. Because of their current roles, these computers are now called servers rather than mainframes.
super Computer
The most powerful computers of that time are commonly called supercomputers. They have historically been very expensive and their use has been limited to high-priority computations for government-sponsored research, such as nuclear simulations and weather modeling. Today many of the computational techniques of early supercomputers are in common use in PCs. On the other hand, the design of expensive, special-purpose processors for supercomputers has been replaced by the use of large arrays of commodity processors (several dozen to more than 8,000) operating in parallel over high-speed communication networks.
Mini Computer
Although minicomputers date back to the early 1950s, the term was introduced in the mid-1960s. Relatively small and inexpensive, minicomputers were typically used in a single department of an organization and were often dedicated to a single task or shared by a small group. Minicomputers generally had limited computational power, but they had excellent compatibility with a variety of laboratory and industrial equipment for collecting and inputting data.
One of the most important manufacturers of minicomputers was Digital Equipment Corporation (DEC), which had a programmable data processor (PDP). DEC’s PDP-1 sold for $120,000 in 1960. Five years later its PDP-8 cost $18,000 and became the first widely used minicomputer to sell over 50,000. The DEC PDP-11, introduced in 1970, came in a variety of models that were small and cheap enough to control a single manufacturing process and large enough for shared use in university computer centers; Over 650,000 were sold. However, microcomputers overtook this market in the 1980s.
Micro
Personal Computers and Peripherals
A microcomputer is a small computer built around a microprocessor integrated circuit or chip. While early minicomputers replaced vacuum tubes with discrete transistors, microcomputers (and later minicomputers too) used microprocessors that integrated thousands or even millions of transistors on a single chip. In 1971, Intel Corporation produced the first microprocessor, the Intel 4004, which was powerful enough to function as a computer, although it was designed for use in Japanese-made calculators. In 1975 the first personal computer, the Altair, used a successor chip, the Intel 8080 microprocessor. Like minicomputers, early microcomputers had relatively limited storage and data-handling capabilities, but these have increased as storage technology improved along with processing power.
In the 1980s it was common to differentiate between microprocessor-based scientific workstations and personal computers. The former used the most powerful microprocessors available and had high-performance color graphics capabilities costing thousands of dollars. They were used by scientists for computation and data visualization, and by engineers for computer-aided engineering. Today the difference between workstation and PC has almost disappeared, PC has the power and performance capability of workstation.
Embedded Processor
Another class of computer is embedded processors. These are small computers that use simple microprocessors to control electrical and mechanical operations. They generally do not need to perform elaborate calculations or be very fast, nor do they have great “input-output” capability, and so can be inexpensive. Embedded processors help control aircraft and industrial automation, and they are common in automobiles and both large and small home appliances. A special type, the digital signal processor (DSP), has become prevalent in the form of microprocessors. DSP can be used for wireless telephone, digital telephone and cable. in a
dems, and some stereo equipment.
Computer Hardware
The physical elements of a computer, its hardware, are generally divided into the central processing unit (CPU), main memory (or random-access memory, RAM), and peripherals. The last class encompasses all sorts of input and output (I/O) devices: keyboard, display monitor, printer, disk drives, network connections, scanners, and more.