The Hardware Components That Serve the Input

Introduction

Hardware is the most visible part of any data arrangement: the equipment such as computers, scanners and printers that is used to capture data, transform it and present it to the user equally output. Although we volition focus mainly on the personal computer (PC) and the peripheral devices that are normally used with it, the aforementioned principles use to the consummate range of computers:

• Supercomputers, a term used to denote the fastest computing engines available at any given time, which are used for running exceptionally enervating scientific applications.
• Mainframe computers, which provide high-capacity processing and data storage facilities to hundreds or even thousands of users operating from (dumb) terminals.
• Servers, which take large data storage capacities enabling users to share files and application software, although processing will typically occur on the user's own motorcar.
• Workstations, which provide high-level performance for individual users in computationally intensive fields such as engineering.
• Personal computers (including laptop/notebook computers) have a continued monitor, keyboard and CPU, and have developed into a user-friendly and flexible business concern tool capable of operating independently or as role of an organizational network.
• Mobile devices such every bit personal digital assistants or the latest generation of cellular telephones, offer maximum portability plus wireless connection to the net, although they do not offer the full functionality of a PC.

And we are already moving into the historic period of wearable computers for medical or security applications, embedded computers in appliances ranging from motor cars to washing machines, and the smart carte which will provide identification, cyberbanking facilities, medical records and more!

Input devices

Data may enter an information system in a diverseness of dissimilar ways, and the input device that is most appropriate will unremarkably depend on the type of data existence entered into the system, how frequently this is washed, and who is responsible for the activity. For example, it would be more efficient to scan a page of typed text into an information organisation rather than retyping information technology, but if this happens very seldom, and if typing staff are readily bachelor, then the cost of the scanner might not exist justified. Withal, all of the input devices described in this chapter accept at least 1 thing in common: the ability to translate non-digital data types such as text, sound or graphics into digital (i.east. binary) format for processing past a computer.

The keyboard

A lot of input yet happens by means of a keyboard. Usually, the information that is entered by ways of a keyboard is displayed on the monitor. The layout of nearly keyboards is similar to that of the original typewriter on which it was modeled. Ironically, this "QWERTY" keyboard layout was originally designed to boring the operator down, so that the keys of the typewriter would not get stuck against each other. This layout at present works counter-productively since a calculator 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 past rearranging the keys (the Dvorak keyboard) or by reducing the number of keys. None of these culling designs has really caught on. Special keyboards accept also been designed for countries that use a non-Roman alphabet, and also for disabled people.

Pointing devices

The now ubiquitous electronic mouse is an essential input device for use with whatever graphical user interface. It consists of a plastic moulded housing, designed to fit snugly in the palm of the manus, with a small brawl at its bottom. Moving the mouse across a apartment surface volition translate the movements into a rolling action of the brawl. This is translated into electronic signals that direct the corresponding movement of a cursor on the computer monitor. Buttons on the mouse tin then exist used to select icons or bill of fare items, or the cursor can exist used to trace drawings on the screen.

The less pop trackball operates exactly like an "upside-downward" mouse except that the ball is much larger and, instead of the mouse being moved over a surface, the user manipulates the ball straight. Since the trackball can exist congenital into the side of the keyboard, it obviates the need for a gratis surface expanse and is therefore handy in situations where desktop surface surface area is at a premium or not available. Originally pop in educational laboratory settings and for laptop computers, trackballs are now mainly bars to exhibition displays and other public terminals.

Touch-screens are estimator monitors that incorporate sensors on the screen console itself or its sides. The user tin indicate or select an surface area or location on the screen by pressing a finger onto the monitor. Calorie-free and bear on pens work on a similar principle, except that a stylus is used, allowing for much finer control. Impact 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-scale touch-sensitive screen of the handheld computer, mainly past means of ticking off pre-divers options, although the fancier models support data entry either past means of a stylized alphabet, which resembles a type of shorthand, or another more sophisticated handwriting recognition interface.

Digitizer tablets likewise use a pressure level sensitive area with a stylus. This can exist used to trace drawings. A similar conceptual approach is used for the bear upon pad that can exist found on the majority of new notebook computers, replacing the more than awkward joystick or trackball. The user controls the cursor by moving a finger across a fairly small rectangular touch on-sensitive area below the keyboard, normally nearly 5 cm past vii cm.

A big number of game interfaces have been developed to provide a more than realistic and natural interface in various gaming situations and simulations: the joy stick, steering bicycle, human 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 more often than not existent-time move control. Contact your nearest game arcade for details.

Although the data glove besides 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 information cable attached; though the latter is being replaced past 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 environs projected onto tiny LCD screens fitted into vision goggles. The figurer generates various imaginary objects, which the user can "pick up" and manipulate past means of the glove. Advanced models fifty-fifty let for tactile feedback past means of small pressure pockets congenital into the glove.

Optical scanners and readers

There are a number of dissimilar optical scanner technologies on the market place.

• Optical Scanners use light-emitting devices to illuminate the press on paper. Depending on how much lite is reflected, a light-sensor determines the position and darkness (or color) of the markings on the paper. Special-purpose optical scanners are in use by postal services to read and / interpret hand-written postal codes. General-purpose scanners are used with personal computers to browse in images or text. These vary from handheld devices (see picture) to flatbed scanners which feed input documents 1 sheet at a time. A common employ of optical scanners is the scanning of black-and-white or colour images and pictures. When scanning text, it is necessary to load additional optical character recognition (OCR) software that converts the scanned raster-image of the text into the equivalent character symbols, so that they can be edited using give-and-take processing software.
• Barcode scanners detect sequences of vertical lines of dissimilar widths, the ubiquitous barcode as constitute also on the dorsum of this book. These scanners have go very popular with retailers due to the fact that all pre-packaged products are at present required to take a product bar code on their packaging, following the standard laid downward by the South African Article Numbering Association (SAANA). Libraries and video shops now besides commonly use bar code scanners. They are more by and large used for tracking and routing large numbers of concrete items such as for asset inventory purposes in many larger organizations, postal items past the postal services and courier services, or for luggage handling by airlines.
• Optical mark readers are capable of reading dark marks on specially designed forms. The red multiple option answer sheets in use at many educational and testing institutions are a good example.

Other input devices

A magnetic carte reader reads the magnetized stripe on the back of plastic credit-card size cards. These cards demand to be pre-recorded post-obit certain standards. Although the cards tin hold simply a tiny amount of information, they are very popular for admission (door) control and financial transactions (ATMs and indicate-of-sale terminals).

Magnetic ink graphic symbol recognition (MICR) uses a special ink (containing magnetizable elements) and a distinct font type. Information technology is used mainly in the banking sector for the processing of cheques.

Touch-tone devices tin can use a voice telephone to contact estimator-based switchboards or enter information directly into remote computers. Many corporate telephone help-lines rely on the client pressing the touch on-tone telephone buttons to route his/her call to the right operator by selecting through a bill of fare of possible options. Southward African banks also enable their clients to perform a number of banking transactions via phone.

Digital cameras allow you to make pictures of physical objects directly in a digital, i.eastward. computer-readable, format. Relatively depression-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, about of these digital cameras tin can as well interface directly with personal computers and are thus condign a popular tool to capture pictures for e-mailing or loading on the world-wide Spider web.

Biometric devices are used to verify personal identity based on fingerprints, iris or retinal scanning, mitt geometry, facial characteristics etc. A scanning device is used to capture key measurements and compare them confronting a database of previously stored information. This type of hallmark is becoming increasingly important in the control of concrete access.

Finally, vox input devices are coming of historic period. Voice-recognition has recently fabricated a strong entry into the market with the availability of low-toll systems that work surprisingly well with today's personal computers. These systems allow for vocalism command of most standard applications (including the operating organization). With voice command, the estimator recognizes a very limited number (50 or less) of often used, programmable system commands ("save", "exit", "print"…) from a variety of users. In fact, these systems are not only used for the interface of estimator programs; they are also slowly making an appearance in consumer appliances, novelty items and fifty-fifty motor cars!

Much more than difficult to achieve than vocalization control, is true voice dictation used to dictate east.thou. a alphabetic character to your word processor. The difficulty is that the computer must non merely distinguish between many tens of thousands of possible words, only it must also recognize the well-nigh unnoticeable breaks in between words, different accents and intonations. Therefore, vocalism dictation typically requires a user to train the voice recognition software past reading standard texts aloud. Nevertheless, for personal purposes and slow typists, voice recognition is rapidly becoming a feasible alternative to the keyboard.

Central Processing Unit (CPU)

Once data has been entered into a figurer, it is acted on by the CPU, which is the existent brain of the estimator. The CPU takes specific programme instructions (usually i at a time), applies them to the input data and transforms the input into output.

Components of the CPU

The CPU has ii major components.

• The Arithmetic and Logic Unit (ALU) executes the actual instructions. It knows how to add or multiply numbers, compare information, or convert data into dissimilar internal formats.
• The Control Unit does the "housekeeping" i.eastward. ensures that the instructions are processed on time, in the proper sequence, and operate on the correct data.

Figure 1: Detailed view of a computer organisation

Types of CPUs

The CPU is an electronic device based on microchip technology, hence it is also often chosen 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 manner beyond our comprehension: a typical CPU can multiply more seven-digit numbers in one 2nd than a human being could do in 10 lifetimes, just uses less energy than a low-cal bulb!

Think of the motor car industry: there are different manufacturers or makes of cars (Volkswagen, Toyota, etc.), each with different models (Golf, Jetta, …), which come up out in different versions (City Golf game, Sports model, coupe, etc.). In improver, there exist custom-made special-purpose cars. It is the same in the estimator scrap concern. At that place are many different types of CPUs on the market. The best-known manufacturer is Intel, which produces the microprocessors for the IBM-uniform personal figurer (PC). Some of its competitors produce clones or imitations (e.one thousand. AMD), others manufacturers produce dissimilar types of microprocessors or concentrate on small-scale 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 8088, followed by the 8086, the 80286, the 386, 486 and the line of Pentium processors.

Speed of processing

How does ane measure the speed of, say a Porsche 911? One could mensurate the time that it takes to drive a given distance e.k. the 900 km from Cape Boondocks to Bloemfontein takes iv'/ii hours (ignoring speed limits and traffic jams). Alternatively, one can indicate how far it can be driven in one standard fourth dimension unit of measurement e.grand. the car moves at a cruising speed of 200 km/60 minutes.

In the same way, one tin can measure the speed of the CPU by checking the time information technology takes to process one single pedagogy. As indicated above, the typical CPU is very fast and an educational activity tin can be done in nigh two billionths of a second. To bargain with these small fractions of time, scientists have devised smaller units: a millisecond (a thousandth of a 2d), a microsecond (a millionth), a nanosecond (a billionth) and a picosecond (a trillionth).

However, instead of indicating the time information technology takes to execute a single education, the processing speed is usually indicated by how many instructions (or computations) a CPU tin execute in a 2nd. This is exactly the inverse of the previous measure; due east.g. if the average instruction takes two billionths of a second (2 nanoseconds) then the CPU tin can execute 500 million instructions per second (or one divided by 2 billionths). The CPU is then said to operate at 500 MIPS or 500 million of instructions per second. In the world of personal computers, one commonly refers to the rate at which the CPU can process the simplest instruction (i.e. the clock rate). The CPU is then rated at 500 MHz (megahertz) where mega indicates million and Hertz means "times or cycles per second". For powerful computers, such as workstations, mainframes and supercomputers, a more complex didactics is used equally the basis for speed measurements, namely the and then-called floating-point operation. Their speed is therefore measured in megaflops (million of floating-point operations per second) or, in the example of very fast computers, teraflops (billions of flops).

In practise, the speed of a processor is dictated by iv different elements: the "clock speed", which indicates how many simple instructions tin be executed per second; the word length, which is the number of bits that tin exist processed past the CPU at whatever i time (64 for a Pentium Four chip); the bus width, which determines the number of bits that tin be moved simultaneously in or out of the CPU; and then the physical design of the bit, in terms of the layout of its private transistors. The latest Pentium processor has a clock speed of about 4 GHz and contains well over 100 meg transistors. Compare this with the clock speed of 5 MHz achieved by the 8088 processor with 29 000 transistors!

Moore'southward Law (see Figure 2) states that processing power doubles for the same cost approximately every 18 months.

Figure ii. Illustration of Moore's Law

Von Neumann versus Parallel CPU Architecture

The traditional model of the computer has one single CPU to process all the information. This is chosen the Von Neumann compages because he engineered this approach to computers in the days when computers were still a dream.

Except for entry-level personal computers, well-nigh computers now have 2, iv, or up to 16 CPUs sharing the master processing load, plus various support processors to handle maths processing, communications, disk I/O, graphics or point processing. In fact many CPU chips now contain multiple "cores" each representing an individual CPU.

Some super-computers that take been designed for massive parallel processing, have up to 64,000 CPUs. These computers are typically used only for specialized applications such as atmospheric condition forecasting or fluid modeling. Today's supercomputers are by and large clusters (tight networks) of many thousands of individual computers.

Possible Future CPU Technologies

Maybe the major time to come competitor of the microchip-based microprocessor is optical computing. Although the technology for developing electronic microchips suggests that CPUs will continue to increase in ability 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: calorie-free (which consists of photons) can travel faster, on narrower paths and does not disperse heat. In theory, one can even procedure 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 even so under development in the research laboratories.

A very experimental culling to optical and electronic technologies is the organic computer. Enquiry indicates that, for sure applications, it is possible to let a circuitous organic molecule act as a archaic information processor. Since even a tiny container filled with the appropriate solutions contains many trillions of these molecules, one obtains in issue a hugely parallel calculator. Although this type of figurer can attack combinatorial problems way beyond the telescopic of traditional architectures, the master problem is that the programming of the bio-figurer 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 ground for a new type of computer architecture. Since quantum states can be in juxtaposition, a register of qubits (a flake 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 mistake-correction. To date, experimental computers with a few qubits have been built simply the empirical validation of the actual usefulness of breakthrough computing nevertheless remains an open up question.

Chief Memory

The function of main memory (likewise referred to as primary memory, chief storage or internal storage) is to provide temporary storage for instructions and data during the execution of a program. Main memory is usually known as RAM, which stands for Random Access Memory. Although microchip-based memory is virtually the only technology used by today's computers, there be many different types of retentiveness fries.

Random Access Memory (RAM)

RAM consists of standard excursion-inscribed silicon microchips that contain many millions of tiny transistors. Very much like the CPU chips, their engineering science follows to the so-chosen 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 (meg characters). They are frequently pre-soldered in sets on tiny memory circuit boards called SIMMS (Single In-line Memory Modules) or DIMMS (Dual …) which slot directly onto the motherboard: the master circuit board that holds the CPU and other essential electronic elements. The biggest disadvantage of RAM is that its contents are lost whenever the power is switched off.

There are many special types of RAM and new acronyms such as EDO RAM, VRAM etc. are being created most on a monthly ground. 2 important types of RAM are:

• Cache retentivity is ultra-fast memory that operates at the speed of the CPU. Access to normal RAM is ordinarily slower than the actual operating speed of the CPU. To avert slowing the CPU down, computers normally incorporate some more than expensive, faster cache RAM that sits in betwixt the CPU and RAM. This cache holds the data and programs that are needed immediately by the CPU. Although today's CPUs already contain an amount of cache on the excursion itself, this on-chip cache is usually supplemented past an additional, larger, enshroud on the motherboard.
• Flash RAM or flash memory consists of special RAM chips on a separate circuit board within a tiny casing. Information technology fits into custom ports on many notebooks, mitt-held computers and digital cameras. Unlike normal RAM, wink retentiveness is non-volatile i.e. it holds information technology contents fifty-fifty without external power, so it is also useful equally a secondary storage device.

Read-Simply Memory (ROM)

A modest simply essential chemical element of any computer, ROM also consists of electronic memory microchips only, unlike RAM, information technology does non lose its contents when the power is switched off. Its function is also very dissimilar from that of RAM. Since it is hard 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. The main awarding of ROM is to store the so-chosen kicking program: the instructions that the computer must follow but later on information technology has been switched on to perform a self-diagnosis and and so tell it how load the operating system from secondary storage. ROM chips are also found in many devices which contain programs that are unlikely to change over a significant period of time, such as telephone switch boards, video recorders or pocket calculators. Just similar RAM, ROM comes in a number of dissimilar forms:

• PROM (Programmable Read-Only Retention) is initially empty and can exist custom-programmed in one case only using special equipment. Loading or programming the contents of ROM is called burning the flake since it is the electronic equivalent of blowing tiny transistor fuses within the chip. Once programmed, ordinary PROMs cannot exist modified later.
• EPROM (Erasable Programmable Read-Only Memory) is similar PROM but, by using special equipment such equally an ultra-violet light gun, the memory contents can be erased so that the EPROM tin exist re-programmed.
• EEPROM (Electrically Erasable Programmable Read-Only Retentiveness) is similar to EPROM but it can be re-programmed using special electronic pulses rather than ultraviolet light so no special equipment is required.

Secondary Storage Devices

Since the chief memory of a figurer has a limited capacity, it is necessary to retain data in secondary storage between different processing cycles. This is the medium used to shop the program instructions every bit well equally the data required for hereafter processing. Most secondary storage devices in use today are based on magnetic or optical technologies.

Disk drives

The disk drive is the most pop secondary storage device, and is constitute in both mainframe and microcomputer environments. The central mechanism of the disk bulldoze is a flat disk, coated with a magnetizable substance. As this deejay rotates, information tin exist read from or written to information technology past means of a head. The head is stock-still on an arm and can move across the radius of the disk. Each position of the arm corresponds to a "track" on the deejay, which can exist visualized as one concentric circle of magnetic data. The data on a track is read sequentially as the disk spins underneath the head. At that place are quite a few different types of disk drives.

In Winchester hard drives, the disk, access arm and read/write heads are combined in one single sealed module. This unit is not normally removable, though there are some models available where the unit as a whole can be swapped in and out of a specially designed drive bay. Since the drives are not handled physically, they are less probable to be contaminated by grit and therefore much more than reliable. Mass production and technology advances have brought dramatic improvements in the storage chapters with Terabyte hard drives being state of the art at the end of 2006. Current disk storage costs as trivial Rl per gigabyte.

Large organizations such as banks, telcos and life insurance companies, require huge amounts of storage space, often in the gild of many terabytes (i terabyte is one million megabytes or a trillion characters). This was typically provided by a roomful of large, high-capacity difficult bulldoze units. Currently, they are being replaced increasingly by redundant arrays of independent disks (RAIDs). A RAID consists of an independently powered cabinet that contains a number (10 to 100) of microcomputer Winchester-type drives only functions as one single secondary storage unit of measurement. The advantage of the RAID is its high-speed admission and relatively low cost. In addition, a RAID provides extra information security by means of its fault-tolerant design whereby critical data is mirrored (stored twice on different drives) thus providing concrete data redundancy. Should a mirrored drive fail, the other bulldoze steps in automatically as a backup.

A low-toll, depression-capacity version of the hard disk was popularized past the microcomputer. The diskette consists of a flexible, magnetic ti^J surface coated mylar disk inside a thin, non-removable, plastic sleeve. The early versions of the diskette were fairly large (8″ or 5W) and had a flexible sleeve, hence the proper name floppy diskette. These accept rapidly been replaced by a diskette version in a sturdier sleeve, the stiffy disk, that despite its smaller size (three Due west') can agree more than data. Although the popular IBM format only holds i,44 megabytes, a number of manufacturers have adult diskette drives that can shop from 100 to 250 megabytes per stiffy. An alternative evolution is the removable disk cartridge, which is similar in structure to an internal hard drive but provides portability, making it useful for backup purposes.

Magnetic tape

While disk and optical storage accept overtaken magnetic record equally the well-nigh popular method of storing data in a estimator, record is still used occasionally – in particular for keeping annal copies of important files.

The main drawback of magnetic tape is that it is not very efficient for accessing data in whatever mode other than strictly sequential order. As an analogy, compare a CD actor (which tin can skip to any track almost instantly) with a music tape recorder (which has to wind the tape all the way through if 1 wants to heed to a song near the end). In computer terms, the power to access any record, track, or even role within a song directly is chosen the direct access method. In the case of the tape recorder one may have to wind laboriously through the tape until one reaches the song required – this is referred to equally the sequential access method.

The high-density diskette and recordable optical disk accept all but eroded the marginal toll advantage that record storage enjoyed. This technology is therefore disappearing fast.

Optical disk storage

Optical disks, on the other mitt, are rapidly condign the storage medium of pick for the mass distribution of information/programs and the backup of data. Similar to deejay storage, data is stored and read from a circular disk. However, instead of a magnetic read head, a tiny laser axle is used to detect microscopic pits burnt onto a plastic disk coated with cogitating material. The pits determine whether most of the light amplification by stimulated emission of radiation lite is reflected back or scattered, thus making for a binary "on" or "off". In contrast to difficult disks, data is not stored in concentric cylinders but in one long continuous spiral rails.

Niggling fact: The spiral track used to store information on a CD is over 6 kilometers long.

A popular optical disk format is the 12-cm CD-ROM. The widespread use of music compact discs has made the engineering science very pervasive and cheap. Production costs for a CD-ROM are less than Rl, even for relatively small product volumes. The drive reader units themselves have also dropped in price and are now hardly more than the cost of a diskette bulldoze. A standard CD-ROM tin can shop 650 megabytes of information and the data tin can exist transferred at many megabytes per second, though accessing non-sequential data takes much longer.

The CD-ROM is a read-only medium. Data cannot exist recorded onto the deejay. The depression toll and relatively large capacity makes the CD-ROM ideally suited to the distribution of software. They are too platonic for the low-cost distribution of big quantities of information such every bit product catalogues, reference materials, conference proceedings, databases, etc. It is indispensable for the storage of multimedia where traditional textual information is supplemented with sound, music, voice, pictures, animation, and even video clips.

The limitation of the read-only format lead to the development of low-cost recordable optical disks. The meaty deejay recordable (CD-R) is a write-once, read-many (WORM) technology. The CD-R drive unit takes a blank optical deejay and burns data onto information technology using a higher-powered laser. This disk tin and so be read and distributed equally an ordinary CD-ROM, with the advantage that the data is not-volatile i.e. permanent. The rapid drop in the cost of drive units and blank recording media (less than R2 per CD-R) is making this a very competitive technology for data backup and pocket-size data distribution.

Although the 650 megabytes initially seemed almost limitless, many multimedia and video applications now require more storage. A new format, the Digital Video Data (DVD) standard increased the capacity of the CD-ROM by providing high-density, double-sided and double-layered CDs. Past combining the increased storage capacity with sophisticated information compression algorithms, a DVD disc can hands store 10 times as much equally a CD, sufficient for a full-length high-quality digital motility picture with many simultaneous audio tracks.

Even the DVD is not sufficient storage capacity and currently 2 optical technologies have been developed to increment storage capacity even further. The basic specification of both HD-DVD and Blu-Ray provide for more 25 GB of storage on a disc although multi-layer Blu-Ray discs with capacities of more than 200 GB have already been developed.

A promising enquiry area involves the use of holographic disk storage whereby data is stored in a three-dimensional way. Though in its infancy, early prototypes promise a many-fold increment in storage capacity and information technology could go the answer to the ever increment storage requirements of the next decade

Figure 3: Comparison of secondary storage devices

Device	Admission Speed	Chapters	Toll
RAM	< 2 nanosec	256 MB (chip)	<R1/MB
Tape	serial but	500 MB-4 GB	<10c/MB
Diskette (iii 1/2″)	300 ms	one,44 MB	R1/MB
PC hard disk drive	ten ms	40-750 GB	<2c/MB
Thousand/F hard deejay	25 ms	100+ GB	R2/MB
CD-ROM	<100 ms	660 MB	<0.1c/MB
CD-R	<100 ms	660 MB	<0.2c/MB
DVD	<100 ms	8 GB	<0.1c/MB
Hd-DVD	<100 ms	thirty GB	?
Blu-Ray	<100 ms	25 GB-200GB	?

Output Devices

The last phase of information processing involves the use of output devices to transform computer-readable data dorsum into an data format that can be processed by humans. As with input devices, when deciding on an output device you need to consider what sort of information is to be displayed, and who is intended to receive information technology.

One stardom that tin exist drawn between output devices is that of hardcopy versus softcopy devices. Hardcopy devices (printers) produce a tangible and permanent output whereas softcopy devices (display screens) present a temporary, fleeting image.

Brandish screens

The desk-bound-based computer screen is the most popular output device. The standard monitor works on the same principle as the normal TV tube: a "ray" gun fires electrically charged particles onto a peculiarly coated tube (hence the name Cathode-Ray Tube or CRT). Where the particles hit the coating, the "blanket" is existence "excited" and emits light. A potent magnetic field guides the particle stream to form the text or graphics on your familiar monitor.

CRTs vary essentially in size and resolution. Screen size is usually measured in inches diagonally across from corner to corner and varies from as petty as 12 or xiv inches for standard PCs, to as much every bit 40+ inches for large demonstration and video-conferencing screens. The screen resolution depends on a number of technical factors.

A technology that has received much impetus from the fast-growing laptop and notebook market is the liquid crystal display (LCD). LCDs have matured quickly, increasing in resolution, dissimilarity, and colour quality. Their main advantages are lower free energy requirements and their thin, flat size. Although alternative technologies are already being explored in research laboratories, they currently boss the "flat display" market.

Organic low-cal-emitting diodes (OLED) tin can generate brighter and faster images than LED technology, and require thinner screens, merely they take less stable colour characteristics, making them more suitable for cellular telephone displays than for computers.

Another screen-related technology is the video project unit. Originally adult for the projection of video films, the current trend towards more portable LCD-based lightweight projectors is fuelled by the needs of computer-driven public presentations. Today's units fit hands into a modest suitcase and project a calculator presentation in very much the same way a slide projector shows a slide presentation. They are rapidly replacing the flat transparent LCD panels that needed to be placed on top of an overhead projection unit. Though the LCD panels are more compact, weigh less and are much cheaper, their image is generally of much poorer quality and less bright.

Printers and plotters

Printers are the most popular output device for producing permanent, paper-based computer output. Although they are all hardcopy devices, a distinction can be made between impact and non-impact printers. With impact printers, a hammer or needle physically hits an inked ribbon to leave an ink impression of the desired shape on the paper. The advantage of the impact printer is that it tin can produce more 1 simultaneous copy by using carbon or chemically-coated paper. Non-affect printers, on the other mitt, have far fewer mechanically moving parts and are therefore much quieter and tend to exist more reliable.

The following are the main types of printers currently in apply.

• Dot-matrix printers used to be the familiar low-toll printers continued to many personal computers. The print head consists of a vertical row of needles each of which is individually controlled by a magnet. Equally the impress head moves horizontally across the newspaper, the individual needles strike the paper (and ribbon in between) equally directed by the control machinery to produce text characters or graphics. A shut inspection of a dot-matrix printout will reveal the constituent dots that make up the text. Although it is one of the cheapest printer options, its impress quality is generally much lower that that of light amplification by stimulated emission of radiation and ink-jet printers. All the same, today's models are quick and give a much better quality by increasing the number of needles.
• Laser printers are quickly growing in marketplace share. They piece of work on the aforementioned principle as the photocopier. A laser beam, toggled on and off very chop-chop, illuminates selected areas on a photograph-sensitive drum, where the light is converted into electrical charge. Every bit the drum rotates into a "bed" of carbon particles ("toner") with the reverse charge, these particles volition attach to the drum. The bare paper is then pressed against the drum so that the particles "rub off onto the paper sheet. The sheet and so passes through a high-temperature area and so that the carbon particles are permanently fused onto the newspaper. Current high-cease light amplification by stimulated emission of radiation printers can cope with extremely large printing volumes, as is required e.thousand. by banks to impress their millions of monthly account statements. The laser technology continues to develop in tandem with photocopier technology. Laser printers can now handle colour printing, double-sided printing or combine with postal service equipment to perforate, fold, address and seal automatically into envelopes. At the lower end of the scale are the low-cost "personal" laser printers, which give a very good printing quality at a relatively small-scale cost.
• Thermal printers employ oestrus to print. The older thermal printers used rut-sensitive paper, similar to the special fax newspaper. A slight heat or pressure will leave a darker area. This produced very cheap merely low-quality output. Currently, thermal-printing applied science is used mainly for loftier-quality color printing. These new thermal printers use colored wax sticks and melt the wax onto the paper. Although they are slower than competing color laser and inkjet technologies, they give a much more vibrant, color-saturated prototype.
• Inkjet printers are probably the near popular low-cost printing technology. Liquid ink is squirted onto the paper in the class of tiny droplets. These printers are most the same price as dot-matrix printers, albeit more expensive in terms of consumables. Their quality is shut to that of the laser printers. Their great reward is that the printers tin can hands be adapted to use coloured ink, thus making popular colour printers.
• Plotters are mainly used for engineering and architectural drawings. A plotter consists of one (or several – in the case of color plotters) pen(s) affixed to an arm. As the arm moves across the sheet of paper, the pen draws lines onto the newspaper. It is ideal for line drawings such as plans, especially in cases where the paper size exceeds that which can be accommodated past the other types of printers.
• Chain and line printers are still popular in mainframe environments for the quick production of large volumes of internal printing. The line printer consists of a horizontal, rotating "drum" with 132 cylinders, each containing a full graphic symbol set. Every bit the 132-column broad newspaper moves upwards past the drum, a line at a time, each one of the 132 hammers on the other side of the paper strikes at the exact moment that the respective cylinder "shows" the correct character. The hammer hits the pulsate (and ink ribbon) and leaves an imprint of the graphic symbol on the newspaper. The chain printer works on the same principle, but uses a horizontally rotating concatenation with engraved characters, instead of a drum. As anyone with some working experience in a big organization knows, the print quality of these "computer printouts" is non very high.

Figure 4-4 compares the diverse output devices in terms of a number of characteristics.

Effigy 4: Comparison of output devices

Device	Technology	Quality	Speed	Duplicates?	Graphics?	Fonts?	Colour?
CRT	softcopy	loftier	very fast	n/a	yes	aye	yes
LCD	softcopy	fair	very fast	n/a	aye	yes	yes
Plotter	hardcopy	fair	slow	no	yes	yes	yes
Concatenation/line printer	hardcopy	low	very fast	yes	no	no	no
Light amplification by stimulated emission of radiation printer	hardcopy	high	fast/fair	no	yes	yes	aye
Dot-Matrix printer	hardcopy	fair	fast/off-white	yes	yes	yes	some
Inkjet printer	hardcopy	skilful	fair	no	yes	yep	yes

Audio-output devices

A blazon of output that is becoming increasingly popular unlike types of audio output. is audio output. There are many dissimilar types of audio output.

• Sound output is required by well-nigh multimedia applications and sophisticated games. The audio card in many of today's personal computers synthesizes audio by drawing from a library of stored sounds, essentially using the aforementioned process as plant in music keyboards. More advanced multimedia workstations are equipped for full stereo multi-channel surround audio and easily surpass many a modernistic hi-fi system in cabling and speaker complexity.
• MIDI in/output. Mod day music production would exist impossible without a vast array of electronic instruments and keyboards. These are typically controlled by a personal computer by ways of Instrument Digital Interface (MIDI), a common standard for linking, controlling and processing electronic music.
• Speech synthesis is the production of spoken language-like output using an artificial vocalism. Although the lack of intonation yet makes the vocalism sound artificial, the technology is reasonably mature and can exist found anywhere from talking clocks and luxury cars to automatic responses for telephonic directory enquiries.

Other Output Devices

Many other, extremely specialized input and output devices have been developed. Procedure command, for case, is a very specialized field but extremely important for automated factories (car manufacturing, canneries), continuous process environments (nuclear plants, refineries) or hazardous places (microbiological research laboratories, space exploration). For these applications, the reckoner relies on a multitude of sensors for its inputs: temperatures, speed, force per unit area, flow rates, weight, position, … These sensor inputs are and so processed by the computers, which in plow control directly robot artillery and other mechanical devices such equally cutters, welding equipment, valves, switches, mixers etc.

South African Perspective

A number of car manufacturers have introduced new model vehicles that optionally includes a vehicle safety system that could reduce road deaths and injuries by foreseeing an unavoidable collision and activating passenger restraint and protection systems before it happens. "Pre-crash rubber" has 3 elements:

• A sensor uses millimeter-moving ridge radar to detect vehicles and obstacles on the road alee.
• An electronic control unit (ECU) determines whether a standoff is imminent based on the position, speed and course of the object. If information technology is…
• The seat belts retract to pull the passengers back into their seats and emergency brake help pressure is built, ready for the driver to striking the pedal.

Until now, vehicle safety devices have only been able to activate after a collision.

The auto's radar, Toyota says, works even in rain and snowfall and is constantly scanning ahead. Newly adult computer software can rapidly determine whether a collision is imminent based on the expected course of the host vehicle as well every bit the position, speed and expected grade of preceding or oncoming vehicles. This could be the solution we demand for South Africa'due south unacceptably high road death charge per unit – all we need is for every Due south African driver to be able to afford the new Toyota!

Beyond the Nuts

Commercial development is fix to begin on the adjacent generation of retentivity: the samarium cube. This technology will permit the storage of upward to one terabyte (m gigabytes) of information in a cubic centimeter of glass. When an extremely short pulse of light amplification by stimulated emission of radiation light is practical to a slice of glass containing the rare globe element samarium, a dot around 400 nanometers in bore becomes luminous, allowing the glass to exist used as an optical retentiveness. These luminous dots can be spaced 100 nanometers apart, and upwards to 2000 layers of dots can be stored and read within a cubic centimeter of glass, producing a 3-dimensional storage medium. The pulse of light used to irradiate the cube lasts for just 1000-trillionth of a second (a femtosecond), because a longer pulse of low-cal will create heat that can cause the drinking glass to crack.

Exercises

PC specifications

A friend of yours wants to buy a personal estimator for her pocket-size, domicile-based service business concern. She wants to use industry-standard software to create brochures, practice accounts and fiscal calculations and maintain a database of customers, suppliers, products and orders. She copied downwards the specifications for a calculator that she saw advertised on Television receiver at a competitive price, but she is not sure whether she would really demand all the components, and she doesn't understand all the technical "buzzwords". As a knowledgeable friend, she has asked you

• to explain in not-technical terms her questions about the diverse components;
• to identify any manifestly incorrect specifications that she might have copied downwards wrongly from the advertisement, and briefly explain why they are incorrect.

The following is her specifications canvas:

Specification	Question	Correct?
i.7 GHz Pentium-Iv	What does "ane.7 GHz" mean?
4 MB RAM	What is RAM used for?
500 GB Hard Deejay	What sort of things would exist stored on the hd?
X50 CD-ROM	Would I apply this to brand backups? If not, what would I employ it for?
32 MB SVGA Graphics card	What does this do?
Stiffy bulldoze	Why do I need one if I have a CD-ROM?
102 keyboard	Should I get any other input devices every bit well?
14" monitor	Is this likely to be a modern flat screen like you get on laptops, or the onetime fashioned sort of monitor?
Color inkjet printer	Why not get a dot-matrix printer?

Input/Output devices

A standard Automatic Teller Auto ("ATM") has a large number of input and output devices. Listing every bit many of its I/O devices every bit you tin can (you lot may include sensors also).

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