Computer , device for processing, storing, and displaying information. Computer once meant a person who did computations, 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, constituent parts, and applications. The second section covers the history of computing.

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## History of computing hardware

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The history of computing hardware covers the developments from early simple devices to aid calculation to modern day computers. Before the 20th century, most calculations were done by humans. Early mechanical tools to help humans with digital calculations, like the abacus , were called "calculating machines", called by proprietary names, or referred to as calculators.

The machine operator was called the computer. The first aids to computation were purely mechanical devices which required the operator to set up the initial values of an elementary arithmetic operation, then manipulate the device to obtain the result.

Later, computers represented numbers in a continuous form, for instance distance along a scale, rotation of a shaft, or a voltage. Numbers could also be represented in the form of digits, automatically manipulated by a mechanical mechanism.

Although this approach generally required more complex mechanisms, it greatly increased the precision of results. The development of transistor technology and then the integrated circuit chip led to a series of breakthroughs, starting with transistor computers and then integrated circuit computers , causing digital computers to largely replace analog computers. Metal-oxide-semiconductor MOS large-scale integration LSI then enabled semiconductor memory and the microprocessor , leading to another key breakthrough, the miniaturized personal computer PC , in the s.

The cost of computers gradually became so low that personal computers by the s, and then mobile computers smartphones and tablets in the s, became ubiquitous. Devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers.

The earliest counting device was probably a form of tally stick. Later record keeping aids throughout the Fertile Crescent included calculi clay spheres, cones, etc. The abacus was early used for arithmetic tasks. What we now call the Roman abacus was used in Babylonia as early as c. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house , a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.

Several analog computers were constructed in ancient and medieval times to perform astronomical calculations. These included the astrolabe and Antikythera mechanism from the Hellenistic world c.

AD ; the astronomical analog computers of other medieval Muslim astronomers and engineers; and the astronomical clock tower of Su Song during the Song dynasty.

The castle clock , a hydropowered mechanical astronomical clock invented by Ismail al-Jazari in , was the first programmable analog computer. This idea was taken up by Leibniz centuries later, and is thus one of the founding elements in computing and information science. Scottish mathematician and physicist John Napier discovered that the multiplication and division of numbers could be performed by the addition and subtraction, respectively, of the logarithms of those numbers.

While producing the first logarithmic tables, Napier needed to perform many tedious multiplications. It was at this point that he designed his ' Napier's bones ', an abacus-like device that greatly simplified calculations that involved multiplication and division.

Since real numbers can be represented as distances or intervals on a line, the slide rule was invented in the s, shortly after Napier's work, to allow multiplication and division operations to be carried out significantly faster than was previously possible. His device greatly simplified arithmetic calculations, including multiplication and division.

William Oughtred greatly improved this in with his circular slide rule. He followed this up with the modern slide rule in , essentially a combination of two Gunter rules , held together with the hands.

Slide rules were used by generations of engineers and other mathematically involved professional workers, until the invention of the pocket calculator. Wilhelm Schickard , a German polymath , designed a calculating machine in which combined a mechanised form of Napier's rods with the world's first mechanical adding machine built into the base.

Because it made use of a single-tooth gear there were circumstances in which its carry mechanism would jam. In , while still a teenager, Blaise Pascal started some pioneering work on calculating machines and after three years of effort and 50 prototypes [14] he invented a mechanical calculator.

Gottfried Wilhelm von Leibniz invented the stepped reckoner and his famous stepped drum mechanism around He attempted to create a machine that could be used not only for addition and subtraction but would utilise a moveable carriage to enable long multiplication and division. Leibniz once said "It is unworthy of excellent men to lose hours like slaves in the labour of calculation which could safely be relegated to anyone else if machines were used.

Leibniz also described the binary numeral system , [21] a central ingredient of all modern computers. However, up to the s, many subsequent designs including Charles Babbage 's machines of the and even ENIAC of were based on the decimal system. Around , Charles Xavier Thomas de Colmar created what would over the rest of the century become the first successful, mass-produced mechanical calculator, the Thomas Arithmometer.

It could be used to add and subtract, and with a moveable carriage the operator could also multiply, and divide by a process of long multiplication and long division. Mechanical calculators remained in use until the s. In , Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by a paper tape constructed from punched cards.

The paper tape could be changed without changing the mechanical design of the loom. This was a landmark achievement in programmability. His machine was an improvement over similar weaving looms. Punched cards were preceded by punch bands, as in the machine proposed by Basile Bouchon. These bands would inspire information recording for automatic pianos and more recently numerical control machine tools.

In the late s, the American Herman Hollerith invented data storage on punched cards that could then be read by a machine. His machines used electromechanical relays and counters. That census was processed two years faster than the prior census had been. By , electromechanical tabulating machines could add, subtract, and print accumulated totals. When the United States instituted Social Security in , IBM punched-card systems were used to process records of 26 million workers.

Leslie Comrie 's articles on punched-card methods and W. Eckert 's publication of Punched Card Methods in Scientific Computation in , described punched-card techniques sufficiently advanced to solve some differential equations [29] or perform multiplication and division using floating point representations, all on punched cards and unit record machines. Such machines were used during World War II for cryptographic statistical processing, as well as a vast number of administrative uses.

The Astronomical Computing Bureau, Columbia University , performed astronomical calculations representing the state of the art in computing. The book IBM and the Holocaust by Edwin Black outlines the ways in which IBM's technology helped facilitate Nazi genocide through generation and tabulation of punch cards based on national census data.

See also: Dehomag. By the 20th century, earlier mechanical calculators, cash registers, accounting machines, and so on were redesigned to use electric motors, with gear position as the representation for the state of a variable. The word "computer" was a job title assigned to primarily women who used these calculators to perform mathematical calculations.

Companies like Friden , Marchant Calculator and Monroe made desktop mechanical calculators from the s that could add, subtract, multiply and divide. It was a small, hand-cranked mechanical calculator and as such, a descendant of Gottfried Leibniz 's Stepped Reckoner and Thomas 's Arithmometer. The ANITA sold well since it was the only electronic desktop calculator available, and was silent and quick.

The tube technology was superseded in June by the U. Charles Babbage , an English mechanical engineer and polymath , originated the concept of a programmable computer. Considered the " father of the computer ", [37] he conceptualized and invented the first mechanical computer in the early 19th century. After working on his revolutionary difference engine , designed to aid in navigational calculations, in he realized that a much more general design, an Analytical Engine , was possible. The input of programs and data was to be provided to the machine via punched cards , a method being used at the time to direct mechanical looms such as the Jacquard loom.

For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later.

It employed ordinary base fixed-point arithmetic. The Engine incorporated an arithmetic logic unit , control flow in the form of conditional branching and loops , and integrated memory , making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.

There was to be a store, or memory, capable of holding 1, numbers of 40 decimal digits each ca. An arithmetical unit , called the "mill", would be able to perform all four arithmetic operations , plus comparisons and optionally square roots.

Initially it was conceived as a difference engine curved back upon itself, in a generally circular layout, [40] with the long store exiting off to one side.

Later drawings depict a regularized grid layout. The programming language to be employed by users was akin to modern day assembly languages.

Loops and conditional branching were possible, and so the language as conceived would have been Turing-complete as later defined by Alan Turing. Three different types of punch cards were used: one for arithmetical operations, one for numerical constants, and one for load and store operations, transferring numbers from the store to the arithmetical unit or back.

There were three separate readers for the three types of cards. The machine was about a century ahead of its time. However, the project was slowed by various problems including disputes with the chief machinist building parts for it.

All the parts for his machine had to be made by hand—this was a major problem for a machine with thousands of parts. Eventually, the project was dissolved with the decision of the British Government to cease funding.

Babbage's failure to complete the analytical engine can be chiefly attributed to difficulties not only of politics and financing, but also to his desire to develop an increasingly sophisticated computer and to move ahead faster than anyone else could follow. This appears to be the first published description of programming, so Ada Lovelace is widely regarded as the first computer programmer.

Following Babbage, although unaware of his earlier work, was Percy Ludgate , a clerk to a corn merchant in Dublin, Ireland.

He independently designed a programmable mechanical computer, which he described in a work that was published in In the first half of the 20th century, analog computers were considered by many to be the future of computing. These devices used the continuously changeable aspects of physical phenomena such as electrical , mechanical , or hydraulic quantities to model the problem being solved, in contrast to digital computers that represented varying quantities symbolically, as their numerical values change.

As an analog computer does not use discrete values, but rather continuous values, processes cannot be reliably repeated with exact equivalence, as they can with Turing machines. The first modern analog computer was a tide-predicting machine , invented by Sir William Thomson , later Lord Kelvin, in It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location and was of great utility to navigation in shallow waters.

His device was the foundation for further developments in analog computing. The differential analyser , a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in by James Thomson , the brother of the more famous Lord Kelvin.

He explored the possible construction of such calculators, but was stymied by the limited output torque of the ball-and-disk integrators. An important advance in analog computing was the development of the first fire-control systems for long range ship gunlaying. When gunnery ranges increased dramatically in the late 19th century it was no longer a simple matter of calculating the proper aim point, given the flight times of the shells.

Today's world runs on computers. Nearly every aspect of modern life involves computers in some form or fashion. As technology is advancing, the scale of computer use is increasing. Computer users include both corporate companies and individuals. Computers are efficient and reliable; they ease people's onerous jobs through software and applications specific to their needs offering convenience. Moreover, computers allow users to generate correct information quickly, hold the information so it is available at any time.

## History of Computers

The history of computing hardware covers the developments from early simple devices to aid calculation to modern day computers. Before the 20th century, most calculations were done by humans. Early mechanical tools to help humans with digital calculations, like the abacus , were called "calculating machines", called by proprietary names, or referred to as calculators. The machine operator was called the computer. The first aids to computation were purely mechanical devices which required the operator to set up the initial values of an elementary arithmetic operation, then manipulate the device to obtain the result. Later, computers represented numbers in a continuous form, for instance distance along a scale, rotation of a shaft, or a voltage.

## Introduction to Computer Information Systems/Print version

Но глаза… твои глаза, - сказал Беккер, чувствуя себя круглым дураком. - Почему они такие красные. Она расхохоталась. - Я же сказала вам, что ревела навзрыд, опоздав на самолет.

Парень загородил ему дорогу.

Он где-то. Халохот повернулся к алтарю. В тридцати метрах впереди продолжалось святое причастие. Падре Херрера, главный носитель чаши, с любопытством посмотрел на одну из скамей в центре, где начался непонятный переполох, но вообще-то это его мало занимало. Иногда кому-то из стариков, которых посетил Святой Дух, становилось плохо. Только и делов - вывести человека на свежий воздух. Халохот отчаянно озирался, но Беккера нигде не было.

Сотни людей стояли на коленях перед алтарем, принимая причастие. Может быть, Беккер был среди. Халохот внимательно оглядывал согнутые спины.

## Computer data storage

Вопреки правилам он часто проникал в шифровалку в уик-энд, чтобы на мощнейших компьютерах погонять программу, над которой работал. - Вот хочу попробовать сделать кое-какую перенастройку да проверить электронную почту, - сказал Хейл. Он смотрел на нее с нескрываемым любопытством.

Сьюзан, - в его голосе послышалась решимость, - я прошу тебя помочь мне найти ключ Хейла. - Что? - Сьюзан встала, глаза ее сверкали. Стратмор подавил желание встать с ней .

Стратмор продолжал: - Внезапно я увидел в Цифровой крепости шанс, который выпадает раз в жизни. Ведь если внести в код ряд изменений, Цифровая крепость будет работать на нас, а не против. Ничего более абсурдного Сьюзан слышать еще не доводилось. Цифровая крепость - не поддающийся взлому код, он погубит агентство. - Если бы я сумел слегка модифицировать этот код, - продолжал Стратмор, - до его выхода в свет… - Он посмотрел на нее с хитрой улыбкой.

Сьюзан потребовалось всего мгновение. Стратмор сразу заметил изумление, мелькнувшее в ее глазах, и взволнованно изложил свой план: - Если бы я получил ключ, то смог бы взломать наш экземпляр Цифровой крепости и внести нужные изменения… - Черный ход, - сказала Сьюзан, мгновенно забыв о том, что Стратмор ей лгал. Она все поняла. - Вроде Попрыгунчика.

- Я протестую. Против вашего присутствия в моем кабинете. Я протестую против ваших инсинуаций в отношении моего заместителя, который якобы лжет. Я протестую… - У нас вирус, сэр. Моя интуиция подсказывает мне… - Что ж, ваша интуиция на сей раз вас обманула, мисс Милкен. В первый раз в жизни.

Беккер перешел чуть ли не на шепот: - Я здесь, чтобы узнать, не нужно ли вам чего-нибудь. - Скажем, принести пару таблеток валиума. Наконец канадец опомнился. - Из консульства? - Его тон заметно смягчился. Беккер кивнул. - Так, значит, вы не по поводу моей колонки. - Нет, сэр. Казалось, старик испытал сильнейшее разочарование. Он медленно откинулся на гору подушек. Лицо его было несчастным.

Н-нет… Не думаю… - Голос его дрожал. Беккер склонился над. - Вам плохо. Клушар едва заметно кивнул: - Просто… я переволновался, наверное.

Сьюзан бросилась к двери, моля Бога, чтобы Стратмор в этот миг включил резервное энергоснабжение и дверь открылась. Увы, ее руки уперлись в холодное стекло. Хейл с перепачканным кровью лицом быстро приближался к.

Его руки снова обхватили ее - одна сдавила левую грудь, другая - талию - и оторвали от двери.

Он поклялся применять все свои знания, весь опыт, всю интуицию для защиты компьютеров агентства, стоивших не один миллион долларов. - Интуиция? - с вызовом проговорил. Не нужно интуиции, чтобы понять: никакая это не диагностика.

- Немедленно. Фонтейн поднял голову и произнес с ледяным спокойствием: - Вот мое решение. Мы не отключаемся.