4 input and output devices

input and ouput

1. INPUT AND OUTPUT
DEVICES
LECTURE # 04 (COMPUTER)

2. INTRODUCTION
•Acomputerinteractswiththeexternalenvironmentviathe
input-output(I/O)devicesattachedtoit.
•Inputdeviceisusedforprovidingdataandinstructionstothe
computer.
•Afterprocessingtheinputdata,computerprovidesoutputto
theuserviatheoutputdevice.
•TheI/Odevicesthatareattached,externally,tothecomputer
machinearealsocalledperipheraldevices.

3. INPUT-OUTPUT UNIT
•AnI/Ounitisacomponentofcomputer.
•TheI/Ounitiscomposedoftwoparts
1.inputunitand
2.outputunit.
•Theinputunitisresponsibleforprovidinginputtothe
computer
•Theoutputunitisforreceivingoutputfromthecomputer.
•Inadditiontoinputdevicesandoutputdevices,somedevices
functionasbothinputandoutputdevices.

5. INPUT UNIT
•Theinputunitgetsthedataandprogramsfromvariousinput
devicesandmakesthemavailableforprocessingtoother
unitsofthecomputer.
•Theinputdataisprovidedthroughinputdevices,suchas—
keyboard,mouse,trackballandjoystick.Inputdatacanalso
beprovidedbyscanningimages,voicerecording,video
recording,etc.
•Theinputunitacceptsinputdatafromtheuserviainput
device,transformstheinputdataincomputeracceptable
formusinginputinterfacefortheinputdeviceandprovides
thetransformedinputdataforprocessing

6. OUTPUT UNIT
•Theoutputunitgetstheprocesseddatafromthecomputer
andsendsittooutputdevicestomakethemavailabletothe
userofcomputer.
•Theoutputdataisprovidedthroughoutputdeviceslike
displayscreen,printer,plotterandspeaker.
•Inbrief,theoutputunitacceptsoutputdatafromcomputer
viaoutputdevice,transformstheoutputinformationto
humanreadableformusingtheoutputinterfaceofoutput
deviceandprovidesthetransformedoutputtouser

7. INPUT DEVICES
•Inputdevicesallowusersandotherapplicationstoinputdata
intothecomputer,forprocessing.Thedatainputtoa
computercanbeintheformoftext,audio,video,etc.
•Inputdevicesareclassifiedasfollows:
•Humandataentrydevices
•Keyboard
•Pointingdevices—mouse,trackball,joystick,digitizingtablet
•Pickdevices—lightpen,touchscreen

8. INPUT DEVICES
•Sourcedataentrydevices
•Audioinput—speechrecognition
•Videoinput—digitalcamera
•Scanner—hand-heldscanner,flat-bedscanner
•OpticalScanner—OCR,OMR,MICR,barcodereader
•Inadditiontotheabovedevices,theinputtoacomputercan
alsobeprovidedfromastoragedeviceonthecomputer,
anothercomputer,oranotherpieceofequipment,suchasa
musicalinstrument,thermometerorsensors.

9. HUMAN DATA ENTRY DEVICE
•Inputdevicesthatrequiredatatobeenteredmanuallytothe
computerareidentifiedashumandataentrydevices.
•Thedatamaybeenteredbytypingorkeyingin,orby
pointingadevicetoaparticularlocation.
1.Keyboard
2.PointingDevices
3.Mouse
4.TrackBall
5.Joystick
6.DigitizingTablet
7.PickDevices
8.LightPen
9.TouchScreen
(Seenotesfordetails)

10. SOURCE DATA ENTRY DEVICES
•Sourcedataentrydevicesareusedforaudioinput,videoinput
andtoenterthesourcedocumentdirectlytothecomputer.
•Sourcedataentrydevicesdonotrequiredatatobetyped-in,
keyed-inorpointedtoaparticularlocation.
1.AudioInputDevice
2.VideoInputDevice
3.OpticalInputDevice
a.Scanner
b.OpticalCharacterRecognition(OCR)
c.MagneticInkCharacterRecognition(MICR)
d.OpticalMarkRecognition(OMR)
e.BarcodeReader

11. AUDIO INPUT DEVICE
•Audioinputcanbeprovidedtothecomputerusinghuman
voiceorspeech.
•Audioinputtothecomputercanbeusedfordifferent
purposes.Itcanbeusedformakingtelephonecalls,for
audioandvideoconferencingoverInternet,torecordvoice,
tocreateaudiofilesandembedthesefilestobesentovere-
mail,or,totranslatespokenwordsintotext,etc.
•Audioinputdeviceslikeamicrophoneisusedtoinputa
person’svoiceintothecomputer.
•Asoundcardtranslatesanalogaudiosignalsfrom
microphoneintodigitalcodesthatthecomputercanstore
andprocess.

12. AUDIO INPUT DEVICE
•Translatingspokenwordsintotextisalsoknownasspeech
recognitionorvoicerecognition.
•Theaudioinputalongwiththesoftwareforvoice
recognitionformsthespeechrecognitionsystemorvoice
recognitionsystem
•Thecomputercanbeoperatedusingvoicecommands.
•Theusercandictatethecommandstothecomputer,instead
oftypingthem.
•Thecomputerhastobetrainedtorecognizethevoiceofuser
usingthespeechpatternsandpronunciationofwords.

13. VIDEO INPUT DEVICE
•Videoinputisprovidedtothecomputerusingvideocameraand
digitalcamera.
•Videocameracancapturefullmotionvideoimages.Theimages
aredigitizedandcanbecompressedandstoredinthecomputer
disk.
•Webcamisacommonvideocameradevice.Itisplacedonthe
computerabovethescreentocapturetheimagesoftheuserwho
isworkingonthecomputer.
•Digitalcameraworkslikevideocamerabutcancapturestill
images.
•Thedigitalcameradigitizesimages,compressesthemandstores
themonamemorycardlikeflashmemory.
•Theinformationfromthedigitalcameracanbebroughtintothe
computer,editedandstored.

14. OPTICAL INPUT DEVICES
•Opticalinputdevicesallowcomputerstouselightasa
sourceofinput.
•Scannerisanexampleofopticalinputdevice.
•Othercommonopticalinputdevicesare
•magneticinkcharacterreaderusedforMagneticInkCharacter
Recognition(MICR),
•opticalmarkreaderusedforOpticalMarkRecognition(OMR),
•opticalcharacterreaderforOpticalCharacterRecognition(OCR)
and
•BarcodeReader

15. SCANNER
•Scannerisusedtoinputdatadirectlyintothecomputerfromthe
sourcedocumentwithoutcopyingandtypingthedata.Theinput
datatobescannedcanbeapicture,atextoramarkonapaper.
•Itisanopticalinputdeviceanduseslightasaninputsourceto
convertanimageintoanelectronicformthatcanbestoredonthe
computer.
•Scanneracceptsthesourcepaperdocument,scansthedocument
andtranslatesitintoabitmapimagetobestoredonthecomputer.
•Scannerscomewithutilitysoftwarethatallowthestoredscanned
documentstobeedited,manipulatedandprinted.
•Hand-heldscannerandflat-bedscannerarethetwocommon
typesofscanners

16. OPTICAL CHARACTER RECOGNITION
(OCR)
•OCRisatechniqueforthescanningofaprintedpage,translating
it,andthenusingtheOCRsoftwaretorecognizetheimageas
ASCIItextthatiseditable.
•OCRusesopticalcharacterreaderforrecognition.Theoptical
characterreaderstoresthescannedimageasbitmapimagewhich
isagridofdots.Thus,youcannoteditthetextthathasbeen
scanned.
•Toeditthescannedtext,youneedOCRsoftware.TheOCR
softwaretranslatesthearrayofdotsintotextthatthecomputer
caninterpretaswordsandletters.
•Torecognizethewordsandlettersoftext,theOCRsoftware
comparesthepatternonthescannedimagewiththepatterns
storedinsidethecomputer.

17. MAGNETIC INK CHARACTER
RECOGNITION (MICR)
•MICRisusedinbankstoprocesslargevolumesofcheques.
•Itisusedforrecognizingthemagneticencodingnumbersprinted
atthebottomofacheque.
•Thenumbersonthechequearehumanreadable,andareprinted
usinganinkwhichcontainsironparticles.Thesenumbersare
magnetized.
•MICRusesmagneticinkcharacterreaderforcharacter
recognition.
•WhenachequeispassedthroughMagneticInkCharacterReader,
themagneticfieldcausesthereadheadtorecognizethe
charactersornumbersofcheque.
•ThereadingspeedofMICRisfasterthanOCR.

18. OPTICAL MARK RECOGNITION (OMR)
•OMRisusedtodetectmarksonapaper.Themarksare
recognizedbytheirdarkness.OMRusesanopticalmarkreaderto
readthemarks.
•TheOMRreaderscanstheforms,detectsthemarkthatis
positionedcorrectlyonthepaperandisdarkerthanthe
surroundingpaper,andpassesthisinformationtothecomputer
forprocessingbyapplicationsoftware.
•Forthis,itusesabeamoflightthatisreflectedonthepaperwith
marks,tocapturepresenceandabsenceofmarks.
•Theopticalmarkreaderdetectsthepresenceofmarkby
measuringthereflectedlight.Thepatternofmarksisinterpreted
andstoredinthecomputer.
•OMRiswidelyusedtoreadanswersofobjectivetypetests,
wherethestudentmarksananswerbydarkeningaparticular
circleusingapencil.

19. BARCODE READER
•Barcodesareadjacentverticallinesofdifferentwidththat
aremachinereadable.
•Goodsavailableatsupermarkets,books,etc.usebarcodefor
identification.
•Barcodesarereadusingreflectivelightbybarcodereaders.
•Thisinformationisinputtothecomputerwhichinterprets
thecodeusingthespacingandthicknessofbars.Hand-held
barcodereadersaregenerallyusedindepartmentalstoresto
readthelabels,andinlibrariestoreadlabelsonbooks.
•Barcodereadersarefastandaccurate.

20. OUTPUT DEVICES
•Outputdevicesprovideoutputtotheuser,whichisgenerated
afterprocessingtheinputdata.
•Theprocesseddata,presentedtotheuserviatheoutputdevices
couldbetext,graphics,audioorvideo.
•Theoutputcouldbeonapaperoronafilminatangibleform,or,
inanintangibleformasaudio,videoandelectronicform.
•Outputdevicesareclassifiedasfollows:
•HardCopyDevices
•Printer
•Plotter
•ComputerOutputonMicrofilm(microfiche)

21. OUTPUT DEVICES
•SoftCopyDevices
•Monitor
•VisualDisplayTerminal
•VideoOutput
•AudioResponse
•Theoutputdevicereceivesinformationfromcomputerina
machinereadableform.
•Thereceivedoutputistranslatedtoahumanunderstandable
form.Thetranslationisdoneusingtheoutputinterfaceof
outputdevice.

22. HARD COPY DEVICES
•Theoutputobtainedinatangibleformonapaperorany
surfaceiscalledhardcopyoutput.
•Thehardcopycanbestoredpermanentlyandisportable.
•Thehardcopyoutputcanbereadorusedwithouta
computer.
•Thedevicesthatgeneratehardcopyoutputarecalledhard
copydevices.
•Printer,plotterandmicrofichearecommonhardcopyoutput
devices.

23. PRINTER
•Aprinterprintstheoutputinformationfromthecomputerontoa
paper.
•Printersaregenerallyusedtoprinttextualinformation,but
nowadaysprintersalsoprintgraphicalinformation.
•Theprintquality(sharpnessandclarityofprint)oftheprinteris
determinedbytheresolutionoftheprinter.
•Resolutionismeasuredindotsperinch(dpi).Printerswithahigh
resolution(moredpi)providebetterqualityoutput.
•Differentkindsofprintersareavailablefordifferenttypesof
applications.
•Printersareclassifiedintotwocategories:
1.impactprinterand
2.non-impactprinter

24. IMPACT PRINTERS
•Impactprintersusethetypewriterapproachofphysically
strikingatypefaceagainstthepaperandinkedribbon.
•Impactprinterscanprintacharacteroranentirelineata
time.
•Impactprintersarelow-costprintersusefulforbulkprinting.
•Dotmatrixprinters,daisywheelprintersanddrumprinters
areexamplesofimpactprinters

25. NON IMPACT PRINTERS
•Non-ImpactPrintersdonothitorimpactaribbontoprint.
•Theyuseelectro-staticchemicalsandink-jettechnologies.
•Non-impactprintersarefasterandquieterthanimpact
printers.
•Theyproducehighqualityoutputandcanbeusedfor
printingtextandgraphicsbothinblackandwhite,andcolor.
•Ink-jetprintersandlaserprintersarenon-impactprinters.

26. PLOTTER
•Aplotterisusedforvectorgraphicsoutputtodrawgraphs,
maps,blueprintsofships,buildings,etc.
•Plottersusepensofdifferentcolors(cyan,magenta,yellow
andblack)fordrawing.
•Plottersdrawcontinuousandaccuratelines,incontrastto
printerswherealineisdrawnascloselyspaceddots.
•Plotterisaslowoutputdeviceandisexpensive.
•Plottersareoftwokinds:
1.drumplotterand
2.flatbedplotter

27. MICROFILM
•Amicrofilmisinaficheorrollformat,andisusedtorecord
computeroutputdirectlyfromthecomputertapeor
cartridge.
•ComputerOutputonMicrofilm(COM)isahighspeedand
lowcostprocess.
•Itcanproducedatainmicrofilmformatamuchfasterspeed
fromthatofapaperprinter
•COMisusedforstoringoutputinbankingandinsurance
applications,medicalXrays,etc.

28. SOFT COPY DEVICES
•Theoutputobtainedinanintangibleformonavisual
display,audiounitorvideounitiscalledsoftcopyoutput.
•Thesoftcopyallowscorrectionstobemade,canbestored,
and,canbesentviaE–tootherusers.
•Thesoftcopyoutputrequiresacomputertobereadorused.
•Thedevicesthatgeneratesoftcopyoutputarecalledsoft
copydevices.
•Visualoutputdeviceslikecomputermonitor,visualdisplay
terminal,videosystemandaudioresponsesystemare
commonsoftcopyoutputdevices.

29. MONITOR
•Monitorisacommonoutputdevice.Themonitorisprovided
alongwiththecomputer,toviewthedisplayedoutput.
•Amonitorisoftwokinds-monochromedisplaymonitor
andcolordisplaymonitor.
•Amonochromedisplaymonitorusesonlyonecolorto
displaytextandcolordisplaymonitorcandisplay256colors
atonetime.
•Monitorsareavailableinvarioussizeslike14,15,17,19
and21inches.
•Animageonthemonitoriscreatedbyaconfigurationof
dots,alsoknownaspixels.

30. MONITOR
•Theclarityofimageonthecomputerscreendependson
threefactors
1.ResolutionofScreen
2.DotPitch
3.RefreshRate
•MonitorscanbeCathodeRayTube(CRT),LiquidCrystal
Display(LCD)orLightEmittingDiode(LED)

31. VISUAL DISPLAY TERMINAL
•AmonitorandkeyboardtogetherareknownasVisualDisplay
Terminal(VDT).
•Akeyboardisusedtoinputdataandmonitorisusedtodisplay
theoutputfromthecomputer.
•Themonitorisconnectedtothecomputerbyacable.
•Terminalsarecategorizedasdumb,smartandintelligent
terminals.
•Thedumbterminalsdonothaveprocessingandprogramming
capabilities.
•Smartterminalshavebuilt-inprocessingcapabilitybutdonot
haveitsownstoragecapacity.
•Intelligentterminalshavebothbuilt-inprocessingandstorage
capacity

32. VIDEO OUTPUT
•Screenimageprojectorordataprojectorisanoutputdevice
thatdisplaysinformationfromthecomputerontoalarge
whitescreen.
•Theprojectorismainlyusedtodisplayvisualoutputtoa
largegatheringofpeoplerequiredforthepurposesof
teaching,training,meetings,conferencepresentations,etc.

33. AUDIO RESPONSE
•Acompletesoundsystemconsistsofsoundcard,microphone,speaker
andtheappropriatesoftware.
•Inadditiontorecordingandplayingthesound,thesoftwareallows
editingofsound,likecutting,copy,amplificationandcreationof
vibrantsoundeffects.
•Audioresponseprovidesaudiooutputfromthecomputer.Audiooutput
devicelikespeakers,headsetorheadphoneisusedforaudiooutput
soundfromcomputer.
•Audiooutputiscommonlyusedforcustomerserviceinairlines,banks,
etc.Itisalsousedinvideoconferences,surveys,etc.
•Audioresponseisusedbyvisuallyimpairedtoreadinformationfrom
thescreen.
•Forspeechimpairedpeople,audioresponsehelpsthemto
communicatewithotherpeople.

34. I/O PORT
•Theperipheraldevicescanbeconnectedtocomputerin
severalways.Devicessuchasnetworkadaptersandsound
cardsareconnectedtoexpansionslotsinsidethecomputer.
•Printersandscannersareconnectedtoportsonthebackside
ofthecomputer.Alsoinaportablecomputer,thePCCard
connectstothePCCardslotonit.
•TheI/Oportsaretheexternalinterfacesthatareusedto
connectinputandoutputdeviceslikeprinter,modemand
joysticktothecomputer.
•TheI/Odevicesareconnectedtothecomputerviatheserial
andparallelports,UniversalSerialBus(USB)port,Firewire
port,etc.

35. I/O PORT
•ParallelPort:Aparallelportisaninterfaceforconnectingeight
ormoredatawires.
•Thedataflowsthroughtheeightwiressimultaneously.Theycan
transmiteightbitsofdatainparallel.Asaresult,parallelports
providehighspeeddatatransmission.
•Parallelportisusedtoconnectprintertothecomputer.
•SerialPort:Aserialporttransmitsonebitofdatathroughasingle
wire.
•Sincedataistransmittedseriallyassinglebits,serialports
provideslowspeeddatatransmission.
•Serialportisusedtoconnectexternalmodems,plotters,barcode
reader,etc.

36. I/O PORT
•USBPort:Nowadays,USBisacommonandpopularexternal
portavailablewithcomputers.
•Normally,twotofourUSBportsareprovidedonaPC.
•USBallowsdifferentdevicestobeconnectedtothecomputer
withoutrequiringre-bootofthecomputer.
•USBalsohastheplugandplayfeaturewhichallowsdevices
readytoberunsimplybypluggingthemtotheUSBport
•Firewire(IEEE1394):Itisusedtoconnectaudioandvideo
multimediadeviceslikevideocamera.Itisanexpensive
technologyandisusedforlargedatamovement.
•HarddiskdriveandnewDVDdrivesconnectthroughfirewire.It
hasdatatransferrateofupto400MB/sec.

37. I/O PORT

38. WORKING OF I/O SYSTEM
•TheworkingofI/OsystemcombinesI/OhardwareandI/O
software.
•TheI/Ohardwareincludesports,busesanddevicecontrollersfor
differentdevices,andI/Odevices.
•TheI/Osoftwareisthedevicedriversoftwarethatmaybe
embeddedwithoperatingsystemorcomeswitheachdevice.
•TheworkingofI/Osystemisdescribedasfollows:
•I/ODevicesareattachedtocomputerviatheportsofcomputer.
Therearemanystandardportsavailableonthebacksideofthe
computercaselikeserialportandparallelport.
•Ifoneormoredevicesuseacommonsetofwires,itiscalleda
bus.Forexample,PCIbus,PCIExpressbus,etc.

39. WORKING OF I/O SYSTEM
•DeviceControlleroperatesonabus,aportoradevice.Itcontrols
thesignalsonthewiresofportorbus.Thecontrollershaveone
ormoreregistersfordataandcontrolsignals.
•Controllermaybesimplelikeaserialportcontrollerforaserial
port,or,complexlikeaSCSIcontroller.Somedeviceshavetheir
ownbuilt-incontrollers.
•DeviceDriverissoftwareviawhichtheoperatingsystem
communicateswiththedevicecontrollers.Eachdevicehasits
owndevicedriver,andadevicecontrollerwhichisspecifictothe
device.
•Thedevicedrivershidethedifferencesamongthedifferent
devicecontrollerandpresentauniforminterfacetotheoperating
system

40. WORKING OF I/O SYSTEM
•ApplicationprogramsuseanI/Odevicebyissuing
commandsandexchangingdatawiththedevicedriver.
•Thedevicedriverprovidescorrectcommandstothe
controller,interpretsthecontrollerregister,andtransfersdata
toandfromdevicecontrollerregistersasrequiredforthe
correctdeviceoperation.