Input and Output Devices (1)

INPUT AND OUTPUTINPUT AND OUTPUT

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Input devicesInput devices

Input devices are the hardware Input devices are the hardware used to translate words, sounds, used to translate words, sounds, images and actions that people images and actions that people understand into a form that the understand into a form that the system unit can process. system unit can process.

Examples of input Examples of input devicesdevices Keyboard Keyboard Pointing devicesPointing devices Scanning devicesScanning devices Image capturing devicesImage capturing devices Audio input devicesAudio input devices

Keyboard Keyboard

Most common ways to input data Most common ways to input data is keyboard.is keyboard.

It converts numbers, letters, and It converts numbers, letters, and special characters that people special characters that people understand into electrical signals.understand into electrical signals.

These signals are sent to and These signals are sent to and processed by the system unit.processed by the system unit.

Common types of keyboardsCommon types of keyboards

Traditional Traditional keyboardskeyboards

Flexible keyboardsFlexible keyboards Ergonomic Ergonomic

keyboardskeyboards Wireless keyboardsWireless keyboards PDA keyboardsPDA keyboards

Features of keyboardFeatures of keyboard Windows keyWindows key : displays the Start menu : displays the Start menu SpacebarSpacebar : enters blank spaces : enters blank spaces

between the charactersbetween the characters Navigation keysNavigation keys : control the cursor or : control the cursor or

insertion point on the screeninsertion point on the screen Numeric keypadNumeric keypad : enters numbers and : enters numbers and

arithmetic symbols and controls cursor arithmetic symbols and controls cursor or insertion point.or insertion point.

Function keysFunction keys : shortcut for specific : shortcut for specific tasks. F1 key displays online Helptasks. F1 key displays online Help

Escape keyEscape key : typically cancels a : typically cancels a selection or procedure.selection or procedure.

Toggle keys Toggle keys : Caps Lock key, scroll : Caps Lock key, scroll key, num key are toggle keys. key, num key are toggle keys. They turn a feature on or off.They turn a feature on or off.

Combination keys Combination keys : Ctrl, Shift, Alt, : Ctrl, Shift, Alt, are combination keys which are combination keys which perform an action when held perform an action when held down in combination with another down in combination with another key. key.

Pointing devicesPointing devices

Pointing devices provide a comfortable Pointing devices provide a comfortable interface with the system unit by interface with the system unit by accepting pointing gestures and accepting pointing gestures and converting them into machine converting them into machine readable input. Example :readable input. Example :

MouseMouse JoystickJoystick Touch screenTouch screen Light penLight pen Stylus Stylus

Mouse Mouse A mouse controls a pointer that is A mouse controls a pointer that is

displayed on the monitor.displayed on the monitor. The mouse pointer usually appears The mouse pointer usually appears

in the shape of an arrow.in the shape of an arrow. A mouse may have one, two or A mouse may have one, two or

three buttons which are used to three buttons which are used to select command options and to select command options and to control the mouse pointer on the control the mouse pointer on the screen.screen.

Some mouse have a wheel button Some mouse have a wheel button that can be rotated to scroll through that can be rotated to scroll through information displayed on the information displayed on the monitor.monitor.

Mechanical Mechanical mousemouse

Optical mouseOptical mouse

Cordless or Cordless or wireless mousewireless mouse Trackball Trackball

Touch Touch surfaces or surfaces or touch padstouch pads

Pointing Pointing stickstick

Joystick Joystick Touch Touch screenscreen

Light penLight pen StylusStylus

Scanning devicesScanning devices

Scanning devices convert scanned Scanning devices convert scanned text and images into a form that text and images into a form that the system unit can process. the system unit can process.

Types of scanning devices:Types of scanning devices:– Optical scannerOptical scanner– Bar code readersBar code readers– Character and mark recognition Character and mark recognition

devicesdevices

Optical scannersOptical scanners

It accepts documents consisting It accepts documents consisting of text and / or images and of text and / or images and converts them to machine converts them to machine readable formreadable form

They recognize light, dark and They recognize light, dark and coloured areas that make up coloured areas that make up individual letters or images.individual letters or images.

Two types of optical scannerTwo types of optical scanner

Portable scanner Flatbed scanner

Bar code readersBar code readers

Used mostly at grocery Used mostly at grocery stores.stores.

They are either handheld They are either handheld wand readers or platform wand readers or platform scanners.scanners.

Contain photoelectric Contain photoelectric cells that scan or read cells that scan or read bar codes or the vertical bar codes or the vertical zebra striped marks zebra striped marks printed on product printed on product containers. containers.

Character and mark Character and mark recognition devicesrecognition devices These are scanners that are able These are scanners that are able

to recognize special characters to recognize special characters and marks.and marks.

Three types of these devices are:Three types of these devices are:– MICRMICR– OCROCR– OMROMR

MICRMICR Magnetic ink character Magnetic ink character

recognition (MICR) – used by recognition (MICR) – used by banks to automatically read the banks to automatically read the unusual numbers on the bottom unusual numbers on the bottom of cheques and deposit slips.of cheques and deposit slips.

A special purpose machine known A special purpose machine known as reader / sorter reads these as reader / sorter reads these numbers and provides input that numbers and provides input that allows bank to efficiently maintain allows bank to efficiently maintain customer account balances.customer account balances.

OCROCR

Optical character recognition Optical character recognition (OCR) uses special pre-printed (OCR) uses special pre-printed character that can be read by a character that can be read by a light source and changed into light source and changed into machine readable code.machine readable code.

Eg: handheld wand reader. Used Eg: handheld wand reader. Used in departmental store.in departmental store.

OMROMR

Optical mark recognition also Optical mark recognition also called mark sensing.called mark sensing.

An OMR device senses the An OMR device senses the presence or absence of a mark, presence or absence of a mark, such as a pencil mark.such as a pencil mark.

OMR is often used to score OMR is often used to score multiple choice tests such as multiple choice tests such as Aptitude test, etc.Aptitude test, etc.

Image capturing Image capturing devicesdevices An optical scanner can make a An optical scanner can make a

digital copy of a photograph.digital copy of a photograph. Image capturing devices create or Image capturing devices create or

capture original images.capture original images. Examples of image capturing Examples of image capturing

devicesdevices– Digital cameraDigital camera– Digital video cameraDigital video camera

Digital cameraDigital camera

They are similar to They are similar to traditional cameras traditional cameras except that images except that images are recorded are recorded digitally on a disk or digitally on a disk or in the camera’s in the camera’s memory rather than memory rather than on film and then on film and then downloaded or downloaded or transferred to you transferred to you computer.computer.

Digital video cameraDigital video camera

They record motion digitally on a They record motion digitally on a disk or in the camera’s memory.disk or in the camera’s memory.

Web cameras are specialized Web cameras are specialized digital video cameras that digital video cameras that capture images and send them to capture images and send them to a computer for broadcast over the a computer for broadcast over the internet.internet.

Audio input devicesAudio input devices

Audio input devices convert Audio input devices convert sounds into a form that can be sounds into a form that can be processed by the system unit.processed by the system unit.

Audio input can take many forms Audio input can take many forms including the human voice and including the human voice and music.music.

Voice Voice

Voice recognition systems use a Voice recognition systems use a microphone, a sound card and microphone, a sound card and special software.special software.

These systems allow users to These systems allow users to operate computers and to create operate computers and to create documents using voice documents using voice commands.commands.

Using the Language bar, you Using the Language bar, you can switch between voice can switch between voice command mode and dictation command mode and dictation mode.mode.

Voice command mode allows Voice command mode allows the user to select menu items, the user to select menu items, toolbars and dialogs box toolbars and dialogs box options.options.

Dictation mode allows the Dictation mode allows the user to dictate text directly user to dictate text directly into a word document.into a word document.

MusicMusic

Musical instrument digital interface Musical instrument digital interface or MIDI is a standard that allows or MIDI is a standard that allows musical instruments to connect to musical instruments to connect to the system unit using a special MIDI the system unit using a special MIDI port.port.

MIDI devices are specialized musical MIDI devices are specialized musical instruments that provide input in the instruments that provide input in the form of encoded digital signals form of encoded digital signals representing musical sounds.representing musical sounds.

MIDI devices can be used to MIDI devices can be used to create, record and play back create, record and play back musical composition.musical composition.

The most commonly used MIDI The most commonly used MIDI devices :devices :– Electronic keyboardElectronic keyboard– MIDI violinsMIDI violins– GuitarsGuitars– celloscellos

Output devicesOutput devices

Output devices are any hardware Output devices are any hardware used to provide or to create used to provide or to create output. They translate output. They translate information that has been information that has been processed by the system unit into processed by the system unit into a form that humans can a form that humans can understand.understand.

Example of output Example of output devicesdevices

MonitorsMonitorsPrintersPrintersAudio outputAudio output

Monitors Monitors

Most frequently used output Most frequently used output device.device.

Also known as display screens or Also known as display screens or video display unit.video display unit.

Output is often is referred to as Output is often is referred to as soft copy.soft copy.

Monitors vary in size, shape and Monitors vary in size, shape and cost.cost.

Features of monitorFeatures of monitor

Important characteristic of monitor is Important characteristic of monitor is its clarity.its clarity.

Clarity refers to the quality and Clarity refers to the quality and sharpness of the displayed images.sharpness of the displayed images.

Other features includeOther features include– ResolutionResolution– Dot pitchDot pitch– Refresh rateRefresh rate– sizesize

ResolutionResolution

It is one of the most important It is one of the most important features.features.

Images are formed on a monitor Images are formed on a monitor by a series of dots or pixels by a series of dots or pixels (picture elements)(picture elements)

Resolution is expressed as a Resolution is expressed as a matrix of these dots or pixels.matrix of these dots or pixels.

Dot PitchDot Pitch

It is the distance between each It is the distance between each pixel.pixel.

New monitors have a dot pitch of New monitors have a dot pitch of 0.31 mm or less.0.31 mm or less.

The lower the dot pitch the The lower the dot pitch the clearer the images produced.clearer the images produced.

Refresh rateRefresh rate

Indicates how often a displayed image Indicates how often a displayed image is updated or redrawn on the monitor.is updated or redrawn on the monitor.

Most monitors operate at a rate of 75 Most monitors operate at a rate of 75 Hertz, which means that the monitor Hertz, which means that the monitor is redrawn 75 times each second.is redrawn 75 times each second.

The faster the refresh rate, the better The faster the refresh rate, the better the quality of images displayed.the quality of images displayed.

SizeSize

Size is measured by the diagonal Size is measured by the diagonal length of a monitor’s viewing length of a monitor’s viewing area.area.

Common sizes are 15, 17, 19 and Common sizes are 15, 17, 19 and 21 inches.21 inches.

The smaller the monitor size the The smaller the monitor size the better the quality of images better the quality of images displayed.displayed.

Types of monitorsTypes of monitors

Cathode ray tubeCathode ray tube Flat panel monitorFlat panel monitor Other monitorsOther monitors

Cathode Ray TubeCathode Ray Tube

Flat panel monitorFlat panel monitor

Two types of flat Two types of flat panel monitorspanel monitors– Passive matrix or Passive matrix or

dual scan monitorsdual scan monitors– Active matrix or thin Active matrix or thin

film transistors (TFT)film transistors (TFT)

Other monitorsOther monitors

E-booksE-books Data projectorsData projectors High definition Television (HDTV)High definition Television (HDTV)

PRINTERSPRINTERS

Printers translate information that Printers translate information that has been processed by the has been processed by the system unit and present the system unit and present the information on paper.information on paper.

Printer output is called hard copy.Printer output is called hard copy.

Features Features

Features of a printer includeFeatures of a printer include– ResolutionResolution– Color capabilityColor capability– SpeedSpeed– Memory Memory

Types of printersTypes of printers

Ink jet printersInk jet printers Laser printerLaser printer Thermal printerThermal printer Other printersOther printers

Ink jet printersInk jet printers

Inkjet printers spray ink at Inkjet printers spray ink at high speed on the surface high speed on the surface of paper.of paper.

Produces letter quality Produces letter quality image.image.

Most widely used.Most widely used. Reliable, quiet and Reliable, quiet and

relatively inexpensive relatively inexpensive cartridges.cartridges.

Prints 17 to 19 pages per Prints 17 to 19 pages per minute of black only output minute of black only output and 13 to 15 pages per and 13 to 15 pages per minute of colour output.minute of colour output.

Laser printerLaser printer

Uses technology similar to Uses technology similar to xerox machine.xerox machine.

Uses a laser light beam to Uses a laser light beam to produce images with produce images with excellent letter and graphics excellent letter and graphics quality.quality.

More expensive than ink jet More expensive than ink jet printers.printers.

Faster and used in Faster and used in applications requiring high applications requiring high quality output.quality output.

Categories of laser printerCategories of laser printer– Personal laser printer : do not Personal laser printer : do not

support colour, are less support colour, are less expensive and used by single expensive and used by single users. Prints 15 to 17 pages a users. Prints 15 to 17 pages a minute.minute.

– Shared laser printer : support Shared laser printer : support colour, are more expensive and colour, are more expensive and used (shared) by a group of used (shared) by a group of users. Prints over 50 pages a users. Prints over 50 pages a minute.minute.

Thermal printerThermal printer

Uses heat elements to produce Uses heat elements to produce images on heat sensitive paper.images on heat sensitive paper.

Earlier these printers were only Earlier these printers were only used in scientific labs to record used in scientific labs to record data.data.

Nowadays colour thermal printers Nowadays colour thermal printers are used to produce very high are used to produce very high quality colour artwork and text.quality colour artwork and text.

Other printersOther printers IncludeInclude

– Dot matrix printerDot matrix printer– PlottersPlotters– Photo printersPhoto printers– Portable printersPortable printers

Audio output devicesAudio output devices

These devices translate audio These devices translate audio information from the computer information from the computer into sounds that people can into sounds that people can understand.understand.

Most widely used audio output Most widely used audio output devices are speakers and devices are speakers and headphones.headphones.

Combination input and Combination input and output devicesoutput devices IncludeInclude

– Fax machineFax machine– Multifunction deviceMultifunction device– Internet telephoneInternet telephone– Terminals Terminals

Fax machineFax machine

Also known as facsimile transmission Also known as facsimile transmission machine.machine.

To send a fax, these devices scan the To send a fax, these devices scan the image of a document converting the light image of a document converting the light and dark areas into a format that can be and dark areas into a format that can be sent electronically over standard telephone sent electronically over standard telephone lines.lines.

To receive a fax, these devices reverse the To receive a fax, these devices reverse the process and print the document using process and print the document using signals received from the telephone line.signals received from the telephone line.

Multifunctional Multifunctional devicesdevices Also known as all in one devices Also known as all in one devices Combine the capability of a Combine the capability of a

scanner, printer, fax and copy scanner, printer, fax and copy machine.machine.

Require less space Require less space Disadvantage is the quality and Disadvantage is the quality and

functions are not good as those of functions are not good as those of separate single purpose devices.separate single purpose devices.

Internet Telephone Internet Telephone

Used for sending and receiving voice Used for sending and receiving voice communication. Operate like a communication. Operate like a traditional telephone.traditional telephone.

Telephony is the transmission of Telephony is the transmission of telephone calls over computer Networks. telephone calls over computer Networks. Also known as Internet telephony.Also known as Internet telephony.

Uses internet rather than traditional Uses internet rather than traditional communication lines to support voice communication lines to support voice communication.communication.

Three approaches areThree approaches are

Computer to computer Computer to computer communication communication

Computer to traditional telephone Computer to traditional telephone communication communication

traditional telephone to traditional telephone to traditional telephone traditional telephone communication communication

Terminals Terminals

Terminal is an input and output device Terminal is an input and output device that connects you to a mainframe or that connects you to a mainframe or other type of computer called a host other type of computer called a host computer or server.computer or server.

Four kinds of terminalsFour kinds of terminals– Dumb terminalDumb terminal– Intelligent terminalIntelligent terminal– Network terminalNetwork terminal– Internet terminalInternet terminal

Dumb terminalDumb terminal It can be used to input and It can be used to input and

receive data, but it cannot receive data, but it cannot process data independently.process data independently.

It is used to gain access and to It is used to gain access and to send information to a computer.send information to a computer.

Such a terminal is used by airline Such a terminal is used by airline reservation clerks to access a reservation clerks to access a mainframe computer for flight mainframe computer for flight informationinformation

Intelligent terminalIntelligent terminal It is a microcomputer with It is a microcomputer with

communication software and a communication software and a telephone hookup (modem) or telephone hookup (modem) or other communication links.other communication links.

These connect the terminal to the These connect the terminal to the larger computer or to the internet.larger computer or to the internet.

Popular type is Net PC.Popular type is Net PC. These are low cost and have only These are low cost and have only

one type of secondary storage (an one type of secondary storage (an internal hard disk drive), a sealed internal hard disk drive), a sealed system unit and no expansion slots.system unit and no expansion slots.

Network terminalNetwork terminal

Also known as thin client or network Also known as thin client or network computer, is a low cost alternative computer, is a low cost alternative to an intelligent terminal.to an intelligent terminal.

Most network terminals do not have Most network terminals do not have a hard disk drive and must rely on a a hard disk drive and must rely on a host computer or server for host computer or server for application and system software.application and system software.

Internet terminalInternet terminal

Also known as web terminal or Also known as web terminal or web appliance.web appliance.

Provides access the internet and Provides access the internet and displays web pages on a standard displays web pages on a standard television set.television set.

They offer internet access without They offer internet access without a micro computer.a micro computer.

Used almost exclusively at home.Used almost exclusively at home.