input and output of computers

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FYBMS A-48

DATE: 14/12/09SIGNATURE:

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Acknowledgement

I Shaikh Riyaz Abdul Salam, thestudent of Nirmala Memorial Foundation Collegeof Commerce and Science, studying in F.Y.B.M.S.A-48, had a great pleasure in presenting myefforts of developing my complete project in avery satisfactory and appreciable manner.

My efforts have been a successdue to the co-operation of the college librarianand my family members.

I owe to my professor and theproject guide, debt of gratitude, expert guidanceand invaluable co-operation without whose help

this project could not have been possible.

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INDEXSr. no. Topic Page

1 COMPUTER 4

TYPES OF COMPUTER 5

PARTS OF COMPUTER 8

2 INPUT DEVICES 15 KEYBOARD 16

MOUSE 21

SCANNER 27

JOYSTICK 35

WEBCAM 38

3 OUTPUT DEVICE 40

SCREEN OR MONITOR 41

SPEAKERS 43

PRINTER 45 PROJECTER 48

PLOTTER 50

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4 BIBLOGRAHY 51

COMPUTERA computer is a device that accepts information (in the form ofdigitalized data) and manipulates it for some result based on aprogram or sequence of instructions on how the data is to beprocessed. Complex computers also include the means for storingdata (including the program, which is also a form of data) forsome necessary duration. A program may be invariable and builtinto the computer (and called logic circuitryas it is onmicroprocessors) or different programs may be provided to thecomputer (loaded into its storage and then started by an

administrator or user). Today's computers have both kinds ofprogramming.

Most histories of the modern computer begin with the AnalyticalEngine envisioned by Charles Babbage following themathematical ideas ofGeorge Boole, the mathematician who firststated the principles of logic inherent in today's digital computer.Babbage's assistant and collaborator, Ada Lovelace, is said tohave introduced the ideas of program loops and subroutines andis sometimes considered the first programmer. Apart from

mechanical calculators, the first really useable computers beganwith the vacuum tube, accelerated with the invention of thetransistor, which then became embedded in large numbers inintegrated circuits, ultimately making possible the relatively low-cost personal computer.

Modern computers inherently follow the ideas of the storedprogram laid out byJohn von Neumann in 1945. Essentially, theprogram is read by the computer one instruction at a time, anoperation is performed, and the computer then reads in the next

instruction, and so on. Recently, computers and programs havebeen devised that allow multiple programs (and computers) towork on the same problem at the same time in parallel. With theadvent of the Internet and higher bandwidth data transmission,programs and data that are part of the same overall project canbe distributed over a network and embody the Sun Microsystemsslogan: "The network is the computer."

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Types of computerMicrocomputers (Personal computers)Microcomputers are the most common type of computers in existence today,whether at work in school or on the desk at home. The term"microcomputer" was introduced with the advent of single chipmicroprocessors. The term "microcomputer" itself, is now practically ananachronism.

These computers include:

Desktop computers

Laptop and notebook computers

Tablet PC Palmtop computers

Personal digital assistants (more commonly known as PDA's)

Programmable calculator

Minicomputers (Midrange computers)A minicomputer (colloquially, mini) is a class of multi-user computers thatlies in the middle range of the computing spectrum, in between the largestmulti-user systems (mainframe computers) and the smallest single-usersystems (microcomputers or personal computers). The contemporary term

for this class of system is midrange computer, such as the higher-endSPARC, POWER and Itanium -based systems from Sun Microsystems, IBM andHewlett-Packard.

Mainframe ComputersThe term mainframe computer was created to distinguish the traditional,large, institutional computer intended to service multiple users from thesmaller, single user machines. These computers are capable of handling andprocessing very large amounts of data quickly. Mainframe computers areused in large institutions such as government, banks and large corporations.These institutions were early adopters of computer use, long before personalcomputers were available to individuals. "Mainframe" often refers tocomputers compatible with the computer architectures established in the1960s. Thus, the origin of the architecture also affects the classification, notjust processing power.

Mainframes are measured in integer operations per second or MIPS. Anexample of integer operation is moving data around in memory or I/Odevices. A more useful industrial benchmark is transaction processing as

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defined by the Transaction Processing Performance Council. Mainframes arebuilt to be reliable for transaction processing as it is commonly understood inthe business world: a commercial exchange of goods, services, or money. Atypical transaction, as defined by the Transaction Processing PerformanceCouncil, would include the updating to a database system for such things as

inventory control (goods), airline reservations (services), or banking (money).A transaction could refer to a set of operations including disk read/writes,operating system calls, or some form of data transfer from one subsystem toanother.

Classes by function

ServersServer usually refer to a computer that is dedicated to providing aservice. For example, a computer dedicated to a database may becalled a "database server". "File servers" manage a large

collection ofcomputer files. "Web servers" process web pagesand web applications. Many smaller servers are actually personalcomputers that have been dedicated to providing services forother computers.

WorkstationWorkstations are computers that are intended to serve one userand may contain special hardware enhancements not found on apersonal computer.

Embedded computersEmbedded computers are computers that are a part of a machineor device. Embedded computers generally execute a programthat is stored in non-volatile memory and is only intended tooperate a specific machine or device. Embedded computers arevery common. Embedded computers are typically required tooperate continuously without being reset or rebooted, and onceemployed in their task the software usually cannot be modified.An automobile may contain a number of embedded computers;

however, a washing machine and a DVD player would containonly one. The central processing units (CPUs) used in embeddedcomputers are often sufficient only for the computationalrequirements of the specific application and may be slower andless expensive than CPUs found in a personal computer.

Supercomputer

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A supercomputer is focused on performing tasks involving intensenumerical calculations such as weather forecasting, fluiddynamics, nuclear simulations, theoretical astrophysics, andcomplex scientific computations. A supercomputer is a computer

that is at the frontline of current processing capacity, particularlyspeed of calculation. The term supercomputer itself is rather fluid,and today's supercomputer tends to become tomorrow's ordinarycomputer. Supercomputer processing speeds are measured infloating point operations per second or FLOPS. Example of floatingpoint operation is the calculation of mathematical equations inreal numbers. In terms of computational capability, memory sizeand speed, I/O technology, and topological issues such asbandwidth and latency, Supercomputers are the most powerful.Supercomputers are very expensive and not cost-effective just to

perform batch or transaction processing. Transaction processingis handled by less powerful computer such as server computer ormainframe.

Parts of the computer7
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Everything inside the computer is connected to acircuit board called the 'motherboard'. Themotherboard has sockets for low-level programming(BIOS), the computer's brain, called a CPU; thecomputer's memory (RAM, ROM and CMOS); and foradd-on cards to control the video (picture), audio(sound), printer and anything else that might beconnected to the computer. You may also find amodem inside on an add-on card.

CPU: stands for 'CentralProcessing Unit' and is the'brain' of the computer. Most

CPU's today are made by Inteland bear such names as'Pentium', 'Pentium Pro' and'Pentium II'. Older Intel CPU'sinclude the 80486 and 80386families. Other manufacturers

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also make CPU's: Motorola for the Macintosh, AMDand Cirrus for PC's and others. The 'speed' of aCPU's processing is measured in megahertz. TheCPU is the place that holds info about the operating

system (DOS or Windows, for example).

RAM: RAM is whatyou know asMemory, as in howmuch memory doesyour computer

have? It is notpermanent memory- the RAM is erasedwhen the computerturns off. Permanentmemory is stored onthe hard drive.Memory is measured in increments ofbits andbytes. Generally the least memory you should everhave with a Pentium computer is 64 MB (megabytes:look up kilo-, mega-, and giga- for more info), andmore is much better. There are places on themotherboard (called slots) for memory modules.The memory modules are small printed circuitboards with memory chips on them and are usuallyeither SIMMs (Single Inline Memory Modules) orDIMMs (Dual Inline Memory Module).Don't confuse this with ROM.

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Thisis an

add-in or expansion board such as a video card,sound card or modem. On every motherboard thereare places to add circuit boards to extend thecapabilities of the computer. The most common

circuit boards used are the internal modem, soundcard, and the video display adapter. There arevarious types of expansion slots that may be on themotherboard. The ISA (Industry StandardsAssociation) expansion slot is the older type andmost of the older circuit boards used this type ofslot. A more sophisticated type of slot is the PCI andthe newer modems, and more sophisticated sound

cards require this type of slot. The newest type slotin a PC is the AGP (Accelerated Graphics Port) slot,which is specifically designed for a video displayadapter. The AGP port enables high performancegraphics capabilities, especially for 3D graphics.The video card controls what you see on themonitor. It determines how many dots across thescreen and down the screen the computer can lookafter. The more dots, the more information or themore detail you can see. The video card alsocontrols how many colors you can see. Mostcomputers today can show anywhere from 256colors to many millions of colors. The sound cardcontrols the sound. Most computers come with

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pretty cheap speakers, and the sound card canprobably produce much better sound than thespeakers can. With good speakers, today's soundcards can make your computer sound as good as a

stereo!

The hard drive uses disks that are made ofaluminum or glass (and therefore 'hard'). Each diskcan store much more information than either afloppy or CD-ROM. Sometimes, there may be several

disks in a hard drive. However, the disks in a normalhard drive can not be removed or replaced. Today,hard drives are measured in gigabytes. That's onethousand million bytes. 1 gigabyte is about 11/3 CD-ROM disks. Sometimes a special cache is used forquick retrieval of often-used information (such asweb pages). This is just a separate directory on thehard drive.

Generally when we talk about a floppydisk drive we are talking about the drivethat uses the 3.5 inch 1.44Mb floppy disk

in it. There have been other types that have come

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some have a roller ball on top and don't require youto actually move the mouse on the desktop. Thereare also programmable mice, touch pads thatsubstitute for a mouse, etc.. The standard types are

the Serial, and the PS/2. The Serial mouse plugs intoone of the 9 pin serial port of your computer(COM1), and the PS/2 mouse plugs into a specialPS/2 port on your computer.

A modem allows yourcomputer to connect to another computer using thenormal telephone line. It converts data from acomputer format, which requires many wires, into aformat that can be sent using only the two wires of atelephone line. At the other end of the telephonewires the process is reversed. Data transfer ratesfrom the modem vary from 14.4Kbs to 56Kbs.(14.4Kbs, 28.8Kbs, 33.6Kbs, 56Kbs) There arespecial types of modems such as cable modems thatcan communicate at much higher data rates.

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The USB (Universal Serial Bus) connector is thenewest type port (connector) on the PC. It isextremely easy to use. You just plug in a USBcompatible device and the computer automaticallyconfigures itself to use the device. The computerdoes not have to be turned off or rebooted. As manyas 127 USB peripherals can be plugged into acomputer at one time. At 12Mbits per second it ismore than 100 times as fast as a serial port. Thenext generation USB motherboards willcommunicate at 480Mbits per second.

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Input DevicesThere are several ways to get new information or input into acomputer. The two most common ways are the keyboard and themouse. The keyboard has keys for characters (letters, numbersand punctuation marks) and special commands. Pressing the keystells the computer what to do or what to write. The mouse has aspecial ball that allows you to roll it around on a pad or desk andmove the cursor around on screen. By clicking on the buttons onthe mouse, you give the computer directions on what to do. Thereare other devices similar to a mouse that can be used in its place.A trackball has the ball on top and you move it with your finger. Atouchpad allows you to move your finger across a pressuresensitive pad and press to click.

Other types of input devices allow you toput images into the computer. A scannercopies a picture or document into thecomputer. There are several types ofscanners and some look very different,but most look like a flat tray with a glass

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pane and a lid to cover it. You can input photographs into acomputer with a digital camera. Photos are taken with the cameraaway from the computer and stored on a memory chip. Then thecamera is plugged into the computer, so that the images can be

downloaded. Another input device is a graphics tablet. A pressuresensitive pad is plugged into the computer. When you draw onthe tablet with the special pen (never use an ink pen or pencil!),the drawing appears on the screen. The tablet and pen can alsobe used like a mouse to move the cursor and click.

KEYBOARDIn computing, a keyboard is an input device, partially modeledafter the typewriter keyboard, which uses an arrangement ofbuttons or keys, to act as mechanical levers or electronicswitches. A keyboard typically has characters engraved or printed

on the keys and each press of a key typically corresponds to asingle written symbol. However, to produce some symbolsrequires pressing and holding several keys simultaneously or insequence. While most keyboard keys produce letters, numbers orsigns (characters), other keys or simultaneous key presses canproduce actions or computer commands.

In normal usage, the keyboard is used to type text and numbersinto a word processor, text editor or other program. In a moderncomputer, the interpretation of keypresses is generally left to the

software. A computer keyboard distinguishes each physical keyfrom every other and reports all keypresses to the controllingsoftware. Keyboards are also used for computer gaming, eitherwith regular keyboards or by using keyboards with special gamingfeatures, which can expedite frequently used keystrokecombinations. A keyboard is also used to give commands to theoperating system of a computer, such as Windows' Control-Alt-

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Delete combination, which brings up a task window or shuts downthe machine

TypesStandardStandard keyboards for desktop computers, such as the 101-key UStraditional keyboards or the 104-key Windows keyboards, include alphabeticcharacters, punctuation symbols, numbers and a variety offunction keys.The internationally-common 102/105 key keyboards have a smaller 'left shift'key and an additional key with some more symbols between that and theletter to its right (usually Z or Y).

Laptop-sizeKeyboards on laptops and notebook computers usually have a shorter traveldistance for the keystroke and a reduced set of keys. They may not have anumerical keypad, and the function keys may be placed in locations thatdiffer from their placement on a standard, full-sized keyboard.

The keyboards on laptops have a shorter travel distance and a reduced setof keys.

Gaming and multimediaKeyboards with extra keys, such as multimedia keyboards, have special keys

for accessing music, web and other frequently used programs and. Forexample, 'ctrl+marked on color-coded keys are used for some softwareapplications and for specialized uses video editing.

Thumb-sizedSmaller keyboards have been introduced for laptops, PDAs,cellphones or users who have a limited workspace. The size of a

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standard keyboard is dictated by the practical consideration thatthe keys must be large enough to be easily pressed by fingers. Toreduce the size of the keyboard, the numeric keyboard to theright of the alphabetic keyboard can be removed, or the size of

the keys can be reduced, which makes it harder to enter text.Another way to reduce the size of the keyboard is to reduce thenumber of keys and use chordingkeyer, i.e. pressing several keyssimultaneously. For example, the GKOS keyboard has beendesigned for small wireless devices. Other two-handedalternatives more akin to a game controller, such as theAlphaGrip, are also used as a way to input data and text. Anotherway to reduce the size of a keyboard is to use smaller buttonsand pack them closer together. Such keyboards, often called a"thumbboard" (thumbing) are used in some personal digitalassistants such as the Palm Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.

NumericNumeric keyboards contain only numbers, mathematical symbolsfor addition, subtraction, multiplication, and division, a decimalpoint, and several function keys (e.g. End, Delete, etc.). They areoften used to facilitate data entry with smaller keyboard-equippedlaptops or with smaller keyboards that do not have a numeric

keypad. A laptop does sometimes have a numeric pad, but not allthe time. These keys are also known as, collectively, a numericpad, numeric keys, or a numeric keypad, and it can consist of thefollowing types of keys:

arithmetic operators such as +, -, *, /

numeric digits 0-9

cursor arrow keys

navigation keys such as Home, End, PgUp, PgDown, etc.

Num Lock button, used to enable or disable the numeric pad

Non-standard or special-use typesChorded

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A keyset or chorded keyboard is a computer input device thatallows the user to enter characters or commands formed bypressing several keys together, like playing a "chord" on a piano.The large number of combinations available from a small number

of keys allows text or commands to be entered with one hand,leaving the other hand free to do something else. A secondaryadvantage is that it can be built into a device (such as a pocket-sized computer) that is too small to contain a normal sizedkeyboard. A chorded keyboard designed to be used while held inthe hand is called a keyer.

VirtualVirtual keyboards, such as the I-Tech Virtual Laser Keyboard,

project an image of a full-size keyboard onto a surface. Sensors inthe projection unit identify which key is being "pressed" and relaythe signals to a computer or personal digital assistant. There isalso a virtual keyboard, the On-Screen Keyboard, for use onWindows. The On-Screen Keyboard is an image of a standardkeyboard which the user controls by using a mouse to hover overthe desired letter or symbol, and then clicks to enter the letter.The On-Screen Keyboard is provided with Windows as anaccessibility aid, to assist users who may have difficulties using a

regular keyboard. The iPhone uses a multi-touch screen to displaya virtual keyboard.

TouchscreensTouchscreens, such as with the iPhone and the OLPC laptop, canbe used as a keyboard. (The OLPC initiative's second computerwill be effectively two tablet touchscreens hinged together like abook. It can be used as a convertibleTablet PC where thekeyboard is one half-screen (one side of the book) which turnsinto a touchscreen virtual keyboard.)

FoldableFoldable (also called flexible) keyboards are made of soft plasticor silicone which can be rolled or folded on itself for travel. Whenin use, these keyboards can conform to uneven surfaces, and aremore resistant to liquids than standard keyboards. These can also

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be connected to portable devices and smartphones. Some modelscan be fully immersed in water, making them popular in hospitalsand laboratories, as they can be disinfected.

A foldable keyboard.Laser/Infrared

Some devices have recently been produced which project akeyboard layout onto any flat surface using a laser. These devicesdetect key presses via infrared, and can artificially produce thetapping or clicking sound of a physical keyboard through theirsoftware.

MouseIn computing, a mouse (plural mouses, mice, or mouse devices.)is a pointing device that functions by detecting two-dimensional

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motion relative to its supporting surface. Physically, a mouseconsists of an object held under one of the user's hands, with oneor more buttons. It sometimes features other elements, such as"wheels", which allow the user to perform various system-

dependent operations, or extra buttons or features can add morecontrol or dimensional input. The mouse's motion typicallytranslates into the motion of a pointer on a display, which allowsfor fine control of a Graphical User Interface.

The name mouse, originated at the Stanford Research Institute,derives from the resemblance of early models (which had a cordattached to the rear part of the device, suggesting the idea of atail) to the common mouse.

The first marketed integrated mouse shipped as a part of a

computer and intended for personal computer navigation camewith the Xerox 8010 Star Information System in 1981. However,the mouse remained relatively obscure until the appearance ofthe Apple Macintosh; in 1984 PC columnistJohn C. Dvorakironically commented on the release of this new computer with amouse: There is no evidence that people want to use thesethings.

A mouse now comes with most computers and many othervarieties can be bought separately.

Mechanical mouse devices

Mechanical mouse, shown with the top cover removed

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Operating an opto-mechanical mouse.1: moving the mouse turns the ball.2: X and Y rollers grip the ball and transfer movement.3: Optical encoding disks include light holes.4: Infrared LEDs shine through the disks.5: Sensors gather light pulses to convert to X and Y vectors.

Bill English, builder of Engelbart's original mouse, invented theball mouse in 1972 while working for Xerox PARC. The ball-mousereplaced the external wheels with a single ball that could rotate inany direction. It came as part of the hardware package of theXerox Alto computer. Perpendicular chopper wheels housed insidethe mouse's body chopped beams of light on the way to light

sensors, thus detecting in their turn the motion of the ball. Thisvariant of the mouse resembled an inverted trackball and becamethe predominant form used with personal computers throughoutthe 1980s and 1990s. The Xerox PARC group also settled on themodern technique of using both hands to type on a full-sizekeyboard and grabbing the mouse when required.

The ball mouse utilizes two rollers rolling against two sides of theball. One roller detects the forwardbackward motion of themouse and other the leftright motion. The motion of these two

rollers causes two disc-like encoder wheels to rotate, interruptingoptical beams to generate electrical signals. The mouse sendsthese signals to the computer system by means of connectingwires. The driver software in the system converts the signals intomotion of the mouse pointer along X and Y axes on the screen.

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Ball mice and wheel mice were manufactured for Xerox by JackHawley, doing business as The Mouse House in Berkeley,California, starting in 1975.

Based on another invention by Jack Hawley, proprietor of the

Mouse House, Honeywell produced another type of mechanicalmouse. Instead of a ball, it had two wheels rotating at off axes.Keytronic later produced a similar product.

Modern computer mice took form at the cole polytechniquefdrale de Lausanne (EPFL) under the inspiration of ProfessorJean-Daniel Nicoud and at the hands ofengineer and watchmakerAndr Guignard. This new design incorporated a single hardrubber mouseball and three buttons, and remained a commondesign until the mainstream adoption of the scroll-wheel mouse

during the 1990s. In 1985, Ren Sommer added a microprocessor toNicoud's and Guignard's design. Through this innovation, Sommer is creditedwith inventing a significant component of the mouse, which made it more"intelligent."

Another type of mechanical mouse, the "analog mouse" (now generallyregarded as obsolete), uses potentiometers rather than encoder wheels, andis typically designed to be plug-compatible with an analog joystick. The"Color Mouse," originally marketed by Radio Shack for their Color Computer(but also usable on MS-DOS machines equipped with analog joystick ports,provided the software accepted joystick input) was the best-known example.

Optical miceAn optical mouse uses a light-emitting diode and photodiodes todetect movement relative to the underlying surface, rather thanmoving some of its parts as in a mechanical mouse.

Early optical mice

Xerox optical mouse chip

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Early optical mice, first demonstrated by two independentinventors in 1980, came in two different varieties:

1. Some, such as those invented by Steve Kirsch ofMIT andMouse Systems Corporation,[21][22] used an infrared LED and a

four-quadrant infrared sensor to detect grid lines printedwith infrared absorbing ink on a special metallic surface.Predictive algorithms in the CPU of the mouse calculated thespeed and direction over the grid.

2. Others, invented by Richard F. Lyon and sold by Xerox, useda 16-pixel visible-light image sensor with integrated motiondetection on the same chip[23][24] and tracked the motion oflight dots in a dark field of a printed paper or similar mousepad.[25]

These two mouse types had very different behaviors, as theKirsch mouse used an x-y coordinate system embedded in thepad, and would not work correctly when the pad was rotated,while the Lyon mouse used the x-y coordinate system of themouse body, as mechanical mice do.

The optical sensor from a Microsoft Wireless IntelliMouse Explorer(v. 1.0A)

Modern optical mice

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Optical mouse sensor disassembled

Modern surface-independent optical mice work by using an

optoelectronicsensor to take successive images of the surface onwhich the mouse operates. As computing power grew cheaper, itbecame possible to embed more powerful special-purpose image-processingchips in the mouse itself. This advance enabled themouse to detect relative motion on a wide variety of surfaces,translating the movement of the mouse into the movement of thepointer and eliminating the need for a special mouse-pad. Thisadvance paved the way for widespread adoption of optical mice.Optical mice illuminate the surface that they track over, using an

LED or a laser diode. Changes between one frame and the nextare processed by the image processing part of the chip andtranslated into movement on the two axes using an optical flowestimation algorithm. For example, the Avago TechnologiesADNS-2610 optical mouse sensor processes 1512 frames persecond: each frame consisting of a rectangular array of 1818pixels, and each pixel can sense 64 different levels of gray.

Laser mice

The laser mouse uses an infraredlaser diode instead of an LED toilluminate the surface beneath their sensor. As early as 1998, SunMicrosystems provided a laser mouse with their Sun SPARCstationservers and workstations. However, laser mice did not enter themainstream market until 2004, when Logitech, in partnership withAgilent Technologies, introduced its MX 1000 laser mouse.[28] Thismouse uses a small infrared laser instead of an LED and hassignificantly increased the resolution of the image taken by themouse. The laser enables around 20 times more surface trackingpower to the surface features used for navigation compared to

conventional optical mice, via interference effects.

A wireless mouse on a mouse pad

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Manufacturers often engineer their optical mice especiallybattery-powered wireless models to save power when possible.In order to do this, the mouse dims or blinks the laser or LEDwhen in standby mode (each mouse has a different standby

time). This function may also increase the laser / LED life. Micedesigned specifically for gamers, such as the Logitech G5 or theRazer Copperhead, often lack this feature in an attempt to reducelatency and to improve responsiveness.

A typical implementation in Logitech mice has four power states,where the sensor is pulsed at different rates per second:

1500 full on condition for accurate response while moving,illumination appears bright.

100 fallback active condition while not moving, illumination

appears dull. 10 standby

2 sleep state

Some other mice turn the sensor fully off in the sleep state,requiring a button click to wake.

Optical mice utilizing infrared elements (LEDs or lasers) offersubstantial increases in battery life. Some Logitech mice, such asthe V450 848 nm laser mouse, are capable of functioning on two

AA batteries for a full year, due to the low power requirements ofthe infrared laser.

Scanner

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Image scanner.

In computing, a scanner is a device that optically scans images,

printed text, handwriting, or an object, and converts it to a digitalimage. Common examples found in offices are variations of thedesktop (or flatbed) scanner where the document is placed on aglass window for scanning. Hand-held scanners, where the deviceis moved by hand, have evolved from text scanning "wands" to3D scanners used for industrial design, reverse engineering, testand measurement, orthotics, gaming and other applications.Mechanically driven scanners that move the document aretypically used for large-format documents, where a flatbed design

would be impractical.Modern scanners typically use a charge-coupled device (CCD) or aContact Image Sensor (CIS) as the image sensor, whereas olderdrum scanners use a photomultiplier tube as the image sensor. Arotary scanner, used for high-speed document scanning, isanother type of drum scanner, using a CCD array instead of aphotomultiplier. Other types of scanners are planetary scanners,which take photographs of books and documents, and 3Dscanners, for producing three-dimensional models of objects.

Another category of scanner is digital camera scanners, which arebased on the concept ofreprographic cameras. Due to increasingresolution and new features such as anti-shake, digital camerashave become an attractive alternative to regular scanners. Whilestill having disadvantages compared to traditional scanners (suchas distortion, reflections, shadows, low contrast), digital camerasoffer advantages such as speed, portability, gentle digitizing of

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thick documents without damaging the book spine. New scanningtechnologies are combining 3D scanners with digital cameras tocreate full-color, photo-realistic 3D models of objects.

In the biomedical research area, detection devices for DNA

microarrays are called scanners as well. These scanners are high-resolution systems (up to 1 m/ pixel), similar to microscopes.The detection is done via CCD or a photomultiplier tube (PMT).

Scanners can be considered the successors of earlytelephotography input devices, consisting of a rotating drum witha single photodetector at a standard speed of 60 or 120 rpm(later models up to 240 rpm). They send a linear analog AM signalthrough standard telephone voice lines to receptors, whichsynchronously print the proportional intensity on special paper.

This system was in use in press from the 1920s to the mid-1990s.Color photos were sent as three separated RGB filtered imagesconsecutively, but only for special events due to transmissioncosts.

Types of Scanner

Drum

Drum scanners capture image information with photomultipliertubes (PMT), rather than the charge-coupled device (CCD) arraysfound in flatbed scanners and inexpensive film scanners.Reflective and transmissive originals are mounted on an acryliccylinder, the scanner drum, which rotates at high speed while itpasses the object being scanned in front of precision optics thatdeliver image information to the PMTs. Most modern color drumscanners use 3 matched PMTs, which read red, blue, and greenlight respectively. Light from the original artwork is split intoseparate red, blue, and green beams in the optical bench of thescanner.

The drum scanner gets its name from the clear acrylic cylinder,the drum, on which the original artwork is mounted for scanning.Depending on size it is possible to mount originals up to 11"x17",but maximum size varies by manufacturer. One of the uniquefeatures of drum scanners is the ability to control sample areaand aperture size independently. The sample size is the area thatthe scanner encoder reads to create an individual pixel. The

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aperture is the actual opening that allows light into the opticalbench of the scanner. The ability to control aperture and samplesize separately is particularly useful for smoothing film grain whenscanning black-and white and color negative originals.

While drum scanners are capable of scanning both reflective andtransmissive artwork, a good-quality flatbed scanner can producegood scans from reflective artwork. As a result, drum scannersare rarely used to scan prints now that high quality inexpensiveflatbed scanners are readily available. Film, however, is wheredrum scanners continue to be the tool of choice for high-endapplications. Because film can be wet-mounted to the scannerdrum and because of the exceptional sensitivity of the PMTs,drum scanners are capable of capturing very subtle details in filmoriginals.

Only a few companies continue to manufacture drum scanners.While prices of both new and used units have come down overthe last decade, they still require a considerable monetaryinvestment when compared to CCD flatbed and film scanners.However, drum scanners remain in demand due to their capacityto produce scans that are superior in resolution, color gradation,and value structure. Also, since drum scanners are capable ofresolutions up to 12,000 PPI, their use is generally recommendedwhen a scanned image is going to be enlarged.

The first scanned image

In most graphic-arts operations, very-high-quality flatbedscanners have replaced drum scanners, being both lessexpensive and faster. However, drum scanners continue

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to be used in high-end applications, such as museum-quality archiving of photographs and print production ofhigh-quality books and magazine advertisements. Inaddition, due to the greater availability of pre-owned

units many fine-art photographers are acquiring drumscanners, which has created a new niche market for themachines.

The first image scanner ever developed was a drumscanner. It was built in 1957 at the US National Bureau ofStandards by a team led by Russell Kirsch. The firstimage ever scanned on this machine was a 5 cm square

photograph of Kirsch's then-three-month-old son, Walden.The black and white image had a resolution of 176 pixelson a side.Flatbed

A flatbed scanner is usually composed of a glass pane (or platen),under which there is a bright light (often xenon or cold cathodefluorescent) which illuminates the pane, and a moving opticalarray in CCD scanning. CCD type scanners typically contain three

rows (arrays) of sensors with red, green, and blue filters. CISscanning consists of a moving set of red, green and blue LEDsstrobed for illumination and a connected monochromaticphotodiode array for light collection. Images to be scanned areplaced face down on the glass, an opaque cover is lowered over itto exclude ambient light, and the sensor array and light sourcemove across the pane, reading the entire area. An image istherefore visible to the detector only because of the light itreflects. Transparent images do not work in this way, and requirespecial accessories that illuminate them from the upper side.Many scanners offer this as an option.

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Scanners typically read red-green-blue color (RGB) data from thearray. This data is then processed with some proprietaryalgorithm to correct for different exposure conditions, and sent tothe computer via the device's input/output interface (usually SCSI

or bidirectional parallel port in machines pre-dating the USBstandard). Color depth varies depending on the scanning arraycharacteristics, but is usually at least 24 bits. High quality modelshave 48 bits or more color depth. The other qualifying parameterfor a scanner is its resolution, measured in pixels per inch (ppi),sometimes more accurately referred to as Samples per inch (spi).Instead of using the scanner's true optical resolution, the onlymeaningful parameter, manufacturers like to refer to theinterpolated resolution, which is much higher thanks to softwareinterpolation. As of 2009[update], a high-end flatbed scanner can

scan up to 5400 ppi and a good drum scanner has an opticalresolution of 12,000 ppi.

Manufacturers often claim interpolated resolutions as high as19,200 ppi; but such numbers carry little meaningful value,because the number of possible interpolated pixels is unlimited.

The size of the file created increases with the square of theresolution; doubling the resolution quadruples the file size. Aresolution must be chosen that is within the capabilities of theequipment, preserves sufficient detail, and does not produce a fileof excessive size. The file size can be reduced for a givenresolution by using "lossy" compression methods such asJPEG, atsome cost in quality. If the best possible quality is requiredlossless compression should be used; reduced-quality files ofsmaller size can be produced from such an image when required(e.g., image designed to be printed on a full page, and a muchsmaller file to be displayed as part of a fast-loading web page).

The third important parameter for a scanner is its density range.A high density range means that the scanner is able to reproduceshadow details and brightness details in one scan.By combining full-color imagery with 3D models, modern hand-held scanners are able to completely reproduce objectselectronically. The addition of 3D color printers enables accurateminiaturization of these objects, with applications across manyindustries and professions.

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Computer connectionScanning the document is only one part of the process. For thescanned image to be useful, it must be transferred from thescanner to an application running on the computer. There are twobasic issues: (1) how the scanner is physically connected to thecomputer and (2) how the application retrieves the informationfrom the scanner.

Direct physical connection to a computer

The amount of data generated by a scanner can be very large: a600 DPI 9"x11" (slightly larger than A4 paper) uncompressed 24-bit image is about 100 megabytes of data which must betransferred and stored. Recent scanners can generate this volume

of data in a matter of seconds, making a fast connectiondesirable.

Scanners communicate to their host computer using one of thefollowing physical interfaces, listing from slow to fast:

Parallel - Connecting through a parallel port is the slowestcommon transfer method. Early scanners had parallel portconnections that could not transfer data faster than 70kilobytes/second. The primary advantage of the parallel portconnection was economic: it avoided adding an interface

card to the computer. GPIB - General Purpose Interface Bus. Certain drumscanners

like the Howtek D4000 featured both a SCSI and GPIBinterface. The latter conforms to the IEEE-488 standard,introduced in the mid 70's. The GPIB-interface has only beenused by a few scanner manufactures, mostly serving theDOS/Windows environment. For Apple Macintosh systems,National Instruments provided a NuBus GPIB interface card.

Small Computer System Interface (SCSI), which is supportedby most computers only via an additional SCSI interfacecard. Some SCSI scanners are supplied together with adedicated SCSI card for a PC, although any SCSI controllercan be used. During the evolution of the SCSI standardspeeds increased, with backwards compatibility; a SCSIconnection can transfer data at the highest speed which

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both the controller and the device support. SCSI has beenlargely replaced by USB and Firewire, one or both of whichare directly supported by most computers, and which areeasier to set up than SCSI.

Universal Serial Bus (USB) scanners can transfer dataquickly, and they are easier to use and cheaper than SCSIdevices. The early USB 1.1 standard could transfer data atonly 1.5 megabytes per second (slower than SCSI), but thelater USB 2.0 standard can theoretically transfer up to 60megabytes per second (although everyday rates are muchlower), resulting in faster operation.

FireWire is an interface that is much faster than USB 1.1 andcomparable to USB 2.0. FireWire speeds are 25, 50, and 100,

400 and 800 megabits per second (but a device may notsupport all speeds). Also known as: IEEE-1394.

Some early scanners used a proprietary interface card ratherthan a standard interface.

Indirect (network) connection to a computerDuring the early nineties, professional flatbed scanners weretargeted to professional users. Some vendors (like Umax) alloweda single scanner connected to a host computer to function as a

scanner accessible by all users within a local computer network.This proved to be very handy to e.g. publishers, print shops, etc.This functionality gradually disappeared after the mid-90's asflatbed scanners became more affordable each year. However, asof 2000 and later, all-in-one multi-purpose devices targeted toserve both (small) offices and consumers usually combine aprinter, scanner, copier and fax into a single apparatus availableto a whole workgroup, providing each individual fax, scan, copyand print functionality.

Output data

The scanned result is a non-compressed RGB image, which can betransferred to a computer's memory. Some scanners compressand clean up the image using embedded firmware. Once on thecomputer, the image can be processed with a raster graphics

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program (such as Photoshop or the GIMP) and saved on a storagedevice (such as a hard disk).

Images are usually stored on a hard disk. Pictures are normallystored in image formats such as uncompressed Bitmap, "non-

lossy" (lossless) compressedTIFF and PNG, and "lossy"compressedJPEG. Documents are best stored inTIFF or PDFformat; JPEG is particularly unsuitable for text. Optical characterrecognition (OCR) software allows a scanned image of text to beconverted into editable text with reasonable accuracy, so long asthe text is cleanly printed and in a typeface and size that can beread by the software. OCR capability may be integrated into thescanning software, or the scanned image file can be processedwith a separate OCR program.

JoystickA joystick is an input device consisting of a stick that pivots on abase and reports its angle or direction to the device it iscontrolling. Joysticks are often used to control video games, andusually have one or more push-buttons whose state can also beread by the computer. A popular variation of the joystick used onmodern video game consoles is the analog stick.

The joystick has been the principal flight control in the cockpit ofmany aircraft, particularly military fast jets, where centre stick orside-stick location may be employed (see also Centre stick vsside-stick).

Joysticks are also used for controlling machines such as cranes,trucks, underwater unmanned vehicles, wheelchairs, surveillancecameras and zero turning radius lawn mowers. Miniature finger-

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the mechanical origins themselves are uncertain. The coining ofthe term 'joystick' may actually be credited to Loraine, as his isthe earliest known usage of the term, although he most certainlydid not invent the device.

The first electrical 2-axis joystick was probably invented around1944 in Germany. The device was developed for targeting theglide bomb Henschel Hs 293 against ship targets. Here, thejoystick was used by an operator to steer the missile towards itstarget. This joystick had on-off switches rather than analoguesensors, i.e. a digital joystick. The signal was transmitted from thejoystick to the missile via radio.

This invention was picked up by someone in the team of scientistsassembled at the Heeresversuchsanstalt in Peenemnde. Here a

part of the team on the German rocket program was developingthe Wasserfall missile, a variant of the V-2 rocket, the firstground-to-air missile. The Wasserfall steering equipmentconverted the electrical signal to radio signals and transmittedthese to the missile.

In the 1960s the use of joysticks became widespread in radio-controlled airplane modelling systems such as the Kwik Flyproduced by Phill Kraft (1964). Kraft Systems eventually becamean important OEM supplier of joysticks to the computer industry

and other users. The first use of joysticks outside the RC aircraftindustry may have been in the control of powered wheelchairssuch as the Permobil (1963). During this time period NASA usedjoysticks as control devices as part of the Apollo missions. Forexample, the lunar lander test models were controlled with ajoystick.

Ralph H. Baer, inventor of television video games and theMagnavox Odyssey console, created the first video game joysticksin 1967. They were analog, using two potentiometers to measure

position.The Atari standard joystick, developed for the Atari 2600 was adigital joystick, with a single 'fire' button, and connected via a DE-9 connector, the electrical specifications for which was for manyyears the 'standard' digital joystick specification. Joysticks werecommonly used as controllers in first and second generationgame consoles, but then gave way to the familiar game pad with

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the Nintendo Entertainment System and Sega Master System in1985 and 86, though joysticks - especially arcade-style ones -were and are popular after-market add-ons for any console.

More recently, analog sticks (or thumbsticks, due to their being

controlled by one's thumbs) have become standard on videogame consoles and have the ability to indicate the stick'sdisplacement from its neutral position. This means that thesoftware does not have to keep track of the position or estimatethe speed at which the controls are moved. These devices usuallyuse a magnetic flux detector to determine the position of thestick.

In the latest aircraft, like most of the Airbus aircraft, the joystickhas found a new lease of life for flight control in the form of a

'sidestick' - a controller similar to a games joystick but which isused to control the electronics. The sidestick saves weight,improves movement and visibility in the cockpit and is said to besafer in the event of an accident than the traditional 'controlyoke'.

WEBCAMA webcam is a video capture device connected to a computer orcomputer network, often using a USB port or, if connected to anetwork, ethernet or Wi-Fi.Their most popular use is for video telephony, permitting a

computer to act as a videophone or video conferencing station.This can be used in messenger programs such as Windows LiveMessenger, Skype and Yahoo messenger services. Other popularuses, which include the recording of video files or even still-images, are accessible via numerous software programs,applications and devices.

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They are well known for their low manufacturing costs andflexibility.Some, for example those used as online trafficcameras, are expensive, rugged professional-grade hardware.

HistoryFirst employed in 1991, a webcam was pointed at the Trojanroom coffee pot in the computer science department ofCambridge University. The camera was finally switched off onAugust 22, 2001. The final image captured by the camera canstill be viewed at its homepage.[ The coffee machine wasrepaired for free by Krups.

The oldest webcam still operating is FogCam at San FranciscoState University, which has been running continuously since1994. One of the most widely reported-on webcam sites wasJenniCam, started in 1996, which allowed Internet users toconstantly observe the life of its namesake, somewhat likereality TV series Big Brother, launched three years later. Morerecently, the website Justin.tv has shown a continuous video andaudio stream from a mobile camera mounted on the head of thesite's star. Other cameras are mounted at bridges, publicsquares and other public places, their output made available ona public Web page in accordance with this original conception of"webcam".

Around the turn of the century, computer hardwaremanufacturers began building webcams directly into laptop anddesktop screens, thus eliminating the need to use an externalUSB or Firewire camera. Gradually webcams came to be usedmore for communication with one person or among a few

people, than for offering a view on a Web page for an indefinitepublic.

Video calling and conferencingAs webcam capabilities have been added to instant messaging,

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text chat services such as AOL Instant Messenger, one-to-onelive video communication over the Internet has now reachedmillions of mainstream PC users worldwide. Improved videoquality has helped webcams encroach on traditional video

conferencing systems. New features such as automatic lightingcontrols, real-time enhancements (retouching, wrinklesmoothing and vertical stretch), automatic face tracking andautofocus assist users by providing substantial ease-of-use,further increasing the popularity of webcams.Webcam features and performance can vary by program,computer operating system and also by the computer'sprocessor capabilities. For example, 'high-quality video' isprincipally available to users of certain Logitech webcams if their

computers have dual-core processors meeting certainspecifications.Video calling support has been included in programs such asYahoo Messenger, AOL Instant Messenger (AIM), Windows LiveMessenger, Skype, iChat, Paltalk (now PaltalkScene), Ekiga,Stickam, Tokbox, Camfrog, Gmail, 6rounds, Meetcam andFilmOn.

Output DevicesOutput devices display information in a way that you can you canunderstand. The most common output device is a monitor. Itlooks a lot a like a TV and houses the computer screen. Themonitor allows you to 'see' what you and the computer are doingtogether.

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Speakers are output devices that allowyou to hear sound from your computer.Computer speakers are just like stereospeakers. There are usually two of them

and they come in various sizes.A printer is another common part of acomputer system. It takes what you seeon the computer screen and prints it onpaper. There are two types of printers. The inkjet printer uses inksto print. It is the most common printer used with home computersand it can print in either black and white or color. Laser printersrun much faster because they use lasers to print. Laser printersare mostly used in businesses. Black and white laser printers arethe most common, but some print in color, too.

SCREENMonitor or display is a piece of electrical equipment whichdisplays images generated by devices such as computers, withoutproducing a permanent record. The monitor comprises the displaydevice, circuitry, and an enclosure. The display device in modernmonitors is typically a thin film transistor liquid crystal display(TFT-LCD), while older monitors use a cathode ray tube (CRT).

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A 19" LG flat-panel LCD monitor.

Imaging Technologies

As with television, many hardware technologies exist fordisplaying computer-generated output:

Liquid crystal display (LCD). TFT LCDs are the most populardisplay device for computers.

Passive LCDs are noted for poor contrast and slow response.They were used in laptops until the mid 1990s.

Thin film transistor. Nearly all modern LCD monitors areTFTs.

Cathode ray tube (CRT)Raster scan computer monitors produce images using

pixels. These were the most popular display device for oldercomputers.

Vector displays, as used on the Vectrex, scientific and radarapplications, and several early arcade machines such asAsteroids use CRT displays because of requirement for adeflection system, although a raster-based display may be used.

Television sets were used by most early personal andhome computers, connecting composite video to the televisionset using a modulator. Resolution and image quality werelimited by the display capabilities of television.

Penetron - military aircraft displays

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Plasma displayVideo projectors use CRT, LCD, DLP, LCoS, and other

technology to emit light to a projection screen. Front projectorsuse screens as reflectors to send light back, while rear

projectors use screens as diffusers to refract light forward. Rearprojectors are often integrated into the same case as theirscreen.

Surface-conduction electron-emitter display (SED) and fieldemission display (FED)

Organic light-emitting diode (OLED) display

SPEAKERS

Computer speakers, or multimedia speakers, are speakersexternal to a computer, that disable the lower fidelity built-inspeaker. They often have a low-power internal amplifier. Thestandard audio connection is a 3.5mm (1/8 inch) stereo jack plug

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often colour-coded lime green (following the PC 99 standard) forcomputer sound cards. A plug and socket for a two-wire (signaland ground) coaxial cable that is widely used to connect analogaudio and video components. Also called a "phono connector,"

rows of RCA sockets are found on the backs of stereo amplifierand numerous A/V products. The prong is 1/8" thick by 5/16" long.A few use an RCA connector for input. There are also USBspeakers which are powered from the 5 volts at 200 milliampsprovided by the USB port, allowing about half a watt of outputpower.

Common featuresFeatures vary by manufacturer, but may include the following:

An LED power indicator.A 3.5-mm (1/8-inch) headphone jack.Controls for volume, and sometimes bass and trebleA remote volume control.

Cost cutting measures and technical compatibilityIn order to cut the cost of computer speakers (unless designedfor premium sound performance), speakers designed forcomputers often lack an AM/FM tuner and other built-in sourcesof audio. However, the male 8th-inch plug can be jury riggedwith "female 8th-inch to female stereo RCA" adapters to workwith stereo system components such as CD/DVD audio/SACDplayers (although computers have CD-ROM drives of their ownwith audio CD support), Audio cassette players, turntables, etc.

Despite being designed for computers, computer speakers areelectrically compatible with the aforementioned stereocomponents. There are even models of computer speakers thathave stereo RCA in jacks.

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Major computer speaker companiesAltec Lansing

Bose Corporation

Creative Labs

Cyber AcousticsDell

Edifier

General Electric

Harman KardonHewlett-Packard

JBL

Klipsch

Logitech

PRINTER

Printer is output Device which gives the output in useracceptable format In computing, a printer is a peripheral whichproduces a hard copy (permanent readable text and/or

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graphics) of documents stored in electronic form, usually onphysical print media such as paper or transparencies. Manyprinters are primarily used as local peripherals, and areattached by a printer cable or, in most newer printers, a USB

cable to a computer which serves as a document source. Someprinters, commonly known as network printers, have built-innetwork interfaces (typically wireless and/or Ethernet), and canserve as a hardcopy device for any user on the network.Individual printers are often designed to support both local andnetwork connected users at the same time. In addition, a fewmodern printers can directly interface to electronic media suchas memory sticks or memory cards, or to image capture devicessuch as digital cameras, scanners; some printers are combinedwith a scanner and/or fax machine in a single unit, and can

function as photocopiers. Printers that include non-printingfeatures are sometimes called Multifunction printers (MFP),Multi-Function Devices (MFD), or All-In-One (AIO) printers. MostMFPs include printing, scanning, and copying among theirfeatures.A Virtual printer is a piece of computer software whose userinterface and API resemble that of a printer driver, but which isnot connected with a physical computer printer.

TYPES OF PRINTERS

Toner-based printers

Toner-based printers work using the Xerographic principle thatis used in most photocopiers: by adhering toner to a light-sensitive print drum, then using static electricity to transfer thetoner to the printing medium to which it is fused with heat andpressure.The most common type of toner-based printer is the laser

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is transferred, or transfixed, to the page.Solid ink printers are most commonly used as color officeprinters, and are excellent at printing on transparencies and

other non-porous media. Solid ink printers can produce excellentresults. Acquisition and operating costs are similar to laserprinters. Drawbacks of the technology include high powerconsumption and long warm-up times from a cold state.Also, some users complain that the resulting prints are difficultto write on (the wax tends to repel inks from pens), and aredifficult to feed through Automatic Document Feeders, but thesetraits have been significantly reduced in later models. Inaddition, this type of printer is only available from one

manufacturer, Xerox, manufactured as part of their XeroxPhaser office printer line is also available by various Xeroxconcessionaires. Previously, solid ink printers weremanufactured by Tektronix, but Tek sold the printing business toXerox in 2001.

UV printersXerox is working on an inkless printer which wil