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.
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Introduction to Computer Information Systems/Print versionVIDEO ON THE TOPIC: Peripherals - CompTIA A+ 220-1001 - 3.6
Hardware is the most visible part of any information system: the equipment such as computers, scanners and printers that is used to capture data, transform it and present it to the user as output. Although we will focus mainly on the personal computer PC and the peripheral devices that are commonly used with it, the same principles apply to the complete range of computers:. And we are already moving into the age of wearable computers for medical or security applications, embedded computers in appliances ranging from motor cars to washing machines, and the smart card which will provide identification, banking facilities, medical records and more!
Data may enter an information system in a variety of different ways, and the input device that is most appropriate will usually depend on the type of data being entered into the system, how frequently this is done, and who is responsible for the activity.
For example, it would be more efficient to scan a page of typed text into an information system rather than retyping it, but if this happens very seldom, and if typing staff are readily available, then the cost of the scanner might not be justified.
However, all of the input devices described in this chapter have at least one thing in common: the ability to translate non-digital data types such as text, sound or graphics into digital i. A lot of input still happens by means of a keyboard. Usually, the information that is entered by means of a keyboard is displayed on the monitor. This layout now works counter-productively since a computer can process keyboard input many times faster than even the fastest typist can manage.
A number of attempts have been made to design alternative layouts by rearranging the keys the Dvorak keyboard or by reducing the number of keys. None of these alternative designs has really caught on. Special keyboards have also been designed for countries that use a non-Roman alphabet, and also for disabled people.
It consists of a plastic moulded housing, designed to fit snugly in the palm of the hand, with a small ball at its bottom. Moving the mouse across a flat surface will translate the movements into a rolling action of the ball. Since the trackball can be built into the side of the keyboard, it obviates the need for a free surface area and is therefore handy in situations where desktop surface area is at a premium or not available.
Originally popular in educational laboratory settings and for laptop computers, trackballs are now mainly confined to exhibition displays and other public terminals. Touch-screens are computer monitors that incorporate sensors on the screen panel itself or its sides. The user can indicate or select an area or location on the screen by pressing a finger onto the monitor. Light and touch pens work on a similar principle, except that a stylus is used, allowing for much finer control.
Touch pens are more commonly used with handheld computers such as personal organizers or digital assistants. They have a pen-based interface whereby a stylus a pen without ink is used on the small touch-sensitive screen of the handheld computer, mainly by means of ticking off pre-defined options, although the fancier models support data entry either by means of a stylized alphabet, which resembles a type of shorthand, or some other more sophisticated handwriting recognition interface.
Digitizer tablets also use a pressure sensitive area with a stylus. This can be used to trace drawings. A similar conceptual approach is used for the touch pad that can be found on the majority of new notebook computers, replacing the more awkward joystick or trackball.
A large number of game interfaces have been developed to provide a more realistic and natural interface in various gaming situations and simulations: the joy stick, steering wheel, foot pedal and other gaming devices. They all perform functions similar to the mouse in that they allow the user to control a cursor or simulate generally real-time motion control.
Contact your nearest game arcade for details. Although the data glove also fits under the previous category, it is technically a lot more complex. It looks like a hand glove but contains a large number of sensors and has a data cable attached; though the latter is being replaced by means of infrared cordless data transmission.
Not only does the data glove allow for full three-dimensional movement but it also senses the position of individual fingers, translating this into a grip. The glove is currently used in virtual reality simulators where the user moves around in an artificially rendered environment projected onto tiny LCD screens fitted into vision goggles.
Advanced models even allow for tactile feedback by means of small pressure pockets built into the glove. A magnetic card reader reads the magnetized stripe on the back of plastic credit-card size cards. These cards need to be pre-recorded following certain standards.
Although the cards can hold only a tiny amount of information, they are very popular for access door control and financial transactions ATMs and point-of-sale terminals. Magnetic ink character recognition MICR uses a special ink containing magnetizable elements and a distinct font type. It is used mainly in the banking sector for the processing of cheques.
Touch-tone devices can use a voice telephone to contact computer-based switchboards or enter information directly into remote computers. South African banks also enable their clients to perform a number of banking transactions via telephone. Digital cameras allow you to make pictures of physical objects directly in a digital, i.
Relatively low-cost digital still picture cameras are now available that capture images directly on electronic disk or RAM media instead of the traditional film. Apart from being very compact, most of these digital cameras can also interface directly with personal computers and are thus becoming a popular tool to capture pictures for e-mailing or loading on the world-wide Web.
Biometric devices are used to verify personal identity based on fingerprints, iris or retinal scanning, hand geometry, facial characteristics etc. A scanning device is used to capture key measurements and compare them against a database of previously stored information.
This type of authentication is becoming increasingly important in the control of physical access. Finally, voice input devices are coming of age. These systems allow for voice control of most standard applications including the operating system.
In fact, these systems are not only used for the interface of computer programs; they are also slowly making an appearance in consumer appliances, novelty items and even motor cars! Much more difficult to achieve than voice control, is true voice dictation used to dictate e. The difficulty is that the computer must not only distinguish between many tens of thousands of possible words, but it must also recognize the almost unnoticeable breaks in between words, different accents and intonations.
Nevertheless, for personal purposes and slow typists, voice recognition is rapidly becoming a viable alternative to the keyboard. Once data has been entered into a computer, it is acted on by the CPU, which is the real brain of the computer.
The CPU takes specific program instructions usually one at a time , applies them to the input data and transforms the input into output. The CPU is an electronic device based on microchip technology, hence it is also often called the microprocessor. It is truly the showcase and culmination of the state-of-the-art in the electronics industry: a tiny silicon-based chip occupying less than 1 square cm contains several millions of transistor elements, measuring less than a thousandth of a millimeter across.
They operate at speeds way beyond our comprehension: a typical CPU can multiply more 7-digit numbers in one second than a human could do in ten lifetimes, but uses less energy than a light bulb! Think of the motor car industry: there are different manufacturers or makes of cars Volkswagen, Toyota, etc. It is the same in the computer chip business. There are many different types of CPUs on the market.
Some of its competitors produce clones or imitations e. AMD , others manufacturers produce different types of microprocessors or concentrate on small volumes of highly specialized or very fast microprocessors. Intel has produced a large number of CPU types: the earliest model used in the Personal Computer was the , followed by the , the , the , and the line of Pentium processors.
How does one measure the speed of, say a Porsche ? One could measure the time that it takes to drive a given distance e. Alternatively, one can indicate how far it can be driven in one standard time unit e. In the same way, one can measure the speed of the CPU by checking the time it takes to process one single instruction.
As indicated above, the typical CPU is very fast and an instruction can be done in about two billionths of a second. To deal with these small fractions of time, scientists have devised smaller units: a millisecond a thousandth of a second , a microsecond a millionth , a nanosecond a billionth and a picosecond a trillionth. However, instead of indicating the time it takes to execute a single instruction, the processing speed is usually indicated by how many instructions or computations a CPU can execute in a second.
This is exactly the inverse of the previous measure; e. In the world of personal computers, one commonly refers to the rate at which the CPU can process the simplest instruction i. For powerful computers, such as workstations, mainframes and supercomputers, a more complex instruction is used as the basis for speed measurements, namely the so-called floating-point operation. Their speed is therefore measured in megaflops million of floating-point operations per second or, in the case of very fast computers, teraflops billions of flops.
The latest Pentium processor has a clock speed of about 4 GHz and contains well over million transistors. Compare this with the clock speed of 5 MHz achieved by the processor with 29 transistors!
The traditional model of the computer has one single CPU to process all the data. This is called the Von Neumann architecture because he engineered this approach to computers in the days when computers were still a dream. Some super-computers that have been designed for massive parallel processing, have up to 64, CPUs.
These computers are typically used only for specialized applications such as weather forecasting or fluid modeling. Perhaps the major future competitor of the microchip-based microprocessor is optical computing.
Although the technology for developing electronic microchips suggests that CPUs will continue to increase in power and speed for at least the next decade or so, the physical limits of the technology are already in sight. Switching from electronic to light pulses offers a number of potential advantages: light which consists of photons can travel faster, on narrower paths and does not disperse heat.
In theory, one can even process different signals each with a different light frequency simultaneously using the same channel. Although the benefits of optical processing technology have already been proven in the areas of data storage CD-Rom, CD-R and communication fibre optics , the more complex all-optical switches required for computing are still under development in the research laboratories.
A very experimental alternative to optical and electronic technologies is the organic computer. Research indicates that, for certain applications, it is possible to let a complex organic molecule act as a primitive information processor.
Although this type of computer can attack combinatorial problems way beyond the scope of traditional architectures, the main problem is that the programming of the bio-computer relies entirely on the bio-chemical properties of the molecules. Another exciting but currently still very theoretical development is the possible use of quantum properties as the basis for a new type of computer architecture.
Since quantum states can exist in juxtaposition, a register of qubits a bit value in quantum state takes on all the possible values simultaneously until it is measured. This could be exploited to speed up extremely parallel algorithms and would affect such areas as encryption, searching and error-correction. To date, experimental computers with a few qubits have been built but the empirical validation of the actual usefulness of quantum computing still remains an open question.
RAM consists of standard circuit-inscribed silicon microchips that contain many millions of tiny transistors. Very much like the CPU chips, their technology follows to the so-called law of Moore, which states that they double in capacity or power for the same price every 18 months.
A RAM chip easily holds hundreds of Megabytes million characters. The biggest disadvantage of RAM is that its contents are lost whenever the power is switched off. Two important types of RAM are:. A small but essential element of any computer, ROM also consists of electronic memory microchips but, unlike RAM, it does not lose its contents when the power is switched off.
Its function is also very different from that of RAM. Since it is difficult or impossible to change the contents of ROM, it is typically used to hold program instructions that are unlikely to change during the lifetime of the computer.
In computing , firmware [a] is a specific class of computer software that provides the low-level control for the device's specific hardware. Firmware can either provide a standardized operating environment for the device's more complex software allowing more hardware-independence , or, for less complex devices, act as the device's complete operating system , performing all control, monitoring and data manipulation functions. Typical examples of devices containing firmware are embedded systems , consumer appliances, computers, computer peripherals, and others. Almost all electronic devices beyond the simplest contain some firmware. Changing the firmware of a device was rarely or never done during its lifetime in the past but is nowadays a common procedure; some firmware memory devices are permanently installed and cannot be changed after manufacture.
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Hardware is the most visible part of any information system: the equipment such as computers, scanners and printers that is used to capture data, transform it and present it to the user as output. Although we will focus mainly on the personal computer PC and the peripheral devices that are commonly used with it, the same principles apply to the complete range of computers:. And we are already moving into the age of wearable computers for medical or security applications, embedded computers in appliances ranging from motor cars to washing machines, and the smart card which will provide identification, banking facilities, medical records and more! Data may enter an information system in a variety of different ways, and the input device that is most appropriate will usually depend on the type of data being entered into the system, how frequently this is done, and who is responsible for the activity. For example, it would be more efficient to scan a page of typed text into an information system rather than retyping it, but if this happens very seldom, and if typing staff are readily available, then the cost of the scanner might not be justified. However, all of the input devices described in this chapter have at least one thing in common: the ability to translate non-digital data types such as text, sound or graphics into digital i.
Все посмотрели на вновь организованный текст, выстроенный в горизонтальную линию. - По-прежнему чепуха, - с отвращением скривился Джабба.
- Смотрите. Это просто бессмысленный набор букв… Слова застряли у него в горле, глаза расширились. - О… Боже ты мой… Фонтейн тоже все понял. Брови его поползли вверх. Он был потрясен.
И прижала ладонь к горлу. - В шифровалке вырубилось электричество.
Согласно словам офицера, который отвел Дэвида в морг, некий канадский турист сегодня утром в панике позвонил в полицию и сказал, что у одного японца в парке случился сердечный приступ. Прибыв на место, офицер увидел мертвого Танкадо, рядом с которым находился упомянутый канадец, и тут же по рации вызвал скорую. Когда санитары отвезли тело Танкадо в морг, офицер попытался расспросить канадца о том, что произошло.
Единственное, что он понял из его сбивчивого рассказа, - это что перед смертью Танкадо отдал кольцо. - Танкадо отдал кольцо? - скептически отозвалась Сьюзан. - Да. Такое впечатление, что он его буквально всучил - канадцу показалось, будто бы он просил, чтобы кольцо взяли. Похоже, этот канадец рассмотрел его довольно внимательно.
- Стратмор остановился и повернулся к Сьюзан.
Человек в очках в тонкой металлической оправе стоял внизу, спиной к Беккеру, и смотрел в направлении площади. Беккер прижал лицо к прорези, чтобы лучше видеть. Иди на площадь, взмолился он мысленно. Тень Гиральды падала на площадь, как срубленная гигантская секвойя.
Фонтейн даже глазом не повел. - Каким временем мы располагаем.
Мне нужно кольцо, - холодно сказал. - Кто вы такой? - потребовала. Беккер перешел на испанский с ярко выраженным андалузским акцентом: - Guardia Civil. Росио засмеялась. - Не может быть! - сказала она по-испански. У Беккера застрял комок в горле. Росио была куда смелее своего клиента. - Не может быть? - повторил он, сохраняя ледяной тон. - Может, пройдем, чтобы я смог вам это доказать.
- Не стану вас затруднять, - ухмыльнулась она, - благодарю за предложение. Но все же кто .
Очевидно, Стратмор вдруг задумался:. У Сьюзан имелся на это ответ. - Коммандер, - она снова попыталась настоять на своем, - нам нужно поговорить. - Минутку! - отрезал Стратмор, вопросительно глядя на Хейла. - Мне нужно закончить разговор. - Он повернулся и направился к своему кабинету. Сьюзан открыла рот, но слова застряли у нее в горле.
- Это плохо. Это очень и очень плохо. - Спокойствие, - потребовал Фонтейн. - На какие же параметры нацелен этот червь. На военную информацию.
Тайные операции. Джабба покачал головой и бросил взгляд на Сьюзан, которая по-прежнему была где-то далеко, потом посмотрел в глаза директору.
- Сэр, как вы знаете, всякий, кто хочет проникнуть в банк данных извне, должен пройти несколько уровней защиты. Фонтейн кивнул.
Джабба стремительно повернулся к ВР. За пределами концентрических окружностей появились две тонкие линии.
Прочитаешь за дверью. А теперь выходи.
Сам я из Валенсии. Что привело вас в Севилью.
И он попытался сделать это в одиночку. Похоже, он и на сей раз добьется своей цели. Ключ совсем. Танкадо мертв.