3 Input Output Devices

8/10/2019 3 Input Output Devices

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Input and OutputThe User Connection


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Input:Getting Data from the User to

the Computer

Keyboard

Pointer Devices

Source data Automation

Keyboard: Part of a PC or a Terminal connected to a computer in another location,

Ergonomic Keyboards

Reduceor minimizerepetitive straininjury of wrists

Providemore natural, comfortable position of wrists,

arms, and hands


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How the Computer Accepts Input From the

Keyboard?


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Mechanical

OpticalCordless

Pointing Devices MouseDevices Used for Games

Devices Used in Laptop

Others

Mouse:Most common pointing device

Types of Mouse:

Short lever with handgrip

Pressing trigger causes actions to take place

TrackballVariation on mechanical mouse

User rolls the ball directly

Often built into laptop computers

Joystick

TouchpadRectangular pressure-sensitive padSliding finger across pad moves pointer

Tapping with finger recognized as click

Pointing stick

Small pressure-sensitive post mounted in center of keyboardPushing post in any direction moves pointer


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Other Pointing Devices

Graphics tabletUser moves stylus or puck across board

Used to create or trace precise drawings

Touch screen Allow user to touch items on screenPosition of finger on screen determines

item to be input into system

Pen-based ComputingUse pen-like stylus to input data

Often used in PDAs or pocket PCs

Source Data Automation:Use of special equipment to collect data.

Magnetic-ink Character Recognition (MICR)

Optical Recognition Devices

Other Sources

MICRUses a machine to read characters

Banking industry is predominant user

Characters preprintedon lower left- hand sideof check

Amount added by MICRinscriber when check is cashed


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Optical Recognition:Uses a light beamtoscan data& Convert To Electrical Signals

Scanners:OCRsoftware required

Flatbed scanner:Scans one page at a time

Sheet fed scanner:Motorized rollers feed sheet across scanner head

Other Optical Recognition Methods

Optical Mark Recognition:Senses marks on piece of paper

Bar Codes:Machine reads a series of vertical marks.

Other Sources

Voice Input:User voice recognition software

Digital Camera: User takes photo that is stored on a chip. Photocan be downloaded to computer

Digital video consists of series of still frames

Web cam used to transmit video over the InternetCan capture video from analog sources with video capture card

Video Input


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Other Optical Recognition Methods

Other Sources Voice Input:User voice recognition software

Digital Camera: User takes photo that is stored on a chip. Photocan be downloaded to computer

Digital video consists of series of still frames

Web cam used to transmit video over the InternetCan capture video from analog sources with video capture card

Video Input


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Output:Information for the UserComputer Screen Technology

Common forms are:Cathode Ray Tube (CRT)

Flat-Panel Screen

Smart DisplayCRT Screens: Display text and graphics

Graphics card converts signals from the CU into the image the user sees

Factors Affecting Performance Scan rate

Resolution (clarity) of screenDot pitch

Video memory

Flat-Panel Screens/ Flat-Panel Screens: Very Thin, Sharp & Easier on eyes

LCD TechnologiesActive-matrix:Uses TFT. Produces brighterimageand can be viewedfrom wider angles.

Passive-matrix:Usesfewer transistors. Cheaper& uses less power.

Gas plasma:Supports very large displays. Viewableat very wide angles.

Smart Display

Each contains its Own ProcessorWireless transmitter-receiver allowsuser to control desktopfrom anywherein the house


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Laser:Uses light beamto print on paper. Produces high- quality output

Ink-jet:Sprays dots of inkfrom jet nozzles. Requires high-quality paper so ink

doesnt smear.Less expensive than laser printers

Two Ways of Printing

Impact Printers:RequirePhysical Contactwith paper. Bubble Jet

Line printer:Usedwith mainframesprinting lengthy reports.

Dot-matrix:May be used in PC.

Non-impact Printers:Doesnt requireanyPhysically Contactwith the paper.

Printers: PortraitorLandscape

Use inAutomated Telephone-Based Customer Service

Two Approaches

Synthesis by Analysis:Analyzes actual human voice, Recordsand Plays Backas needed.

Synthesis by rule: uses linguistic rulesto create Ar tif icial Speech

Voice Output:


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Combine Input & Output Capabilities

Terminals

Dumb Terminal: Keyboard for input& monitor for output.No

processing capability

Intelligent Terminal: combines a keyboard and monitor with

memory and a processor. Ability to perform limited processing functions

Point-of-Sale (POS) Terminal: Captures retail sales data when

transaction takes place


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Storage and Multimedia

The Facts and More


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Secondary Storage:Unlike memory data is not lostwhen power is lost

Space

Reliability

Convenience

Economy

Benefits of Secondary Storage

Storage Media:Hardware components that Write data to & Read data from.

Storage Device:Hardware components through which the system Writes &

Reads data in the media.Magnetic Storage

Optical Storage

Hybrid

Type of Storage Devices:

Magnetic Disk Storage: Data represented asMagnetized Spotson surface of

spinning disk. Spots Convert to electrical impulses.

Primary Types

Diskettes

Hard Disks

Storage Device:


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3 Diskette:holds 1.44 MB of data

Sonys HiFD:holds 200 MB

Imations Super Disk:available in 120 and 240 MB versions

Iomegas Zip drive:available in 100, 250, and 750 MB versions

Diskettes:Madeofflexible Plastic Mylar& CoatedwithIron Oxide.

HDDmay have 1,000 or more Tracks on each surface of each platter

Track:

The Circular Portionof the disk surface that passes under the read/write head

A Floppy has 80 Tracks& 18 Sectors. So it has total of

1440 X 2. So a floppy can hold about 1.44MBof data.

Sector:Each track is divided into sectors that hold a fixed number

of bytes. Typically 512 bytesper sector


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Several platters can be Combined into a disk pack

Large computer systems may haveseveral external HDD.

Capacity in gigabytes

SataorIomegasJaz drive is very popular.

Hard Disks:Rigid platterCoated with MagneticOxide.

HDD Crashes:Access arm moves read/write head over platter. If head touches

platter, a head crash occurs and data is destroyed.

Disk Packs:Disk packs combinePlatters,Access Arms, andRead/Write Head


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Optical Disk Storage:A Laser uses a concentrated, narrow beam of l ight,

focused and directed withLenses,Prisms& Sensor.

Categorized by read/write capability

Read Only Media (ROM):user can read from, but not write to disk.

Write Once, Read Many (WORM):user can write to disk once

Magneto Optical: combines magnetic and optical capabilities

How CD-ROM

Drive Works?

CD: CD-ROM:Read Only. Stores up to 700 MB

CD-R: Write to DiskOnce.

CD-RW:Erase and Recordover data multiple times.

Capacity up to 17GB, allows full-length movies, Sound is better than on audio CDsDVD:

Blue Ray Disk: 100GB Capacity


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Magnetic Tape Storage

Tape similar to tape used in music cassettes

Categorized in terms of density. Number of bits per

inch stored on tape

Used primarily for backup of data stored on disk

systems

Backup Systems

It is wise to have copies of data stored away from computer

Disks occasionally fail

Software installation can cause computer to crash

Users make mistakes entering data

Tape is ideal backup medium

Can copy entire hard disk to single tape in minutes

Backup can be scheduled when you are not going to use the systemEnd


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Probable Question

END

1) What is Computer? Describe 4 primary components

of a Computer System.

2) Describe the Classification of Computers.

3) What is Central Processing Unit? Describe Control

Unit & The Arithmetic Logic Unit.

4) How data is Transforming into Information?Explain Decimal & Binary Systems and Bits &

Bytes.

5) Describe the Factors Affecting Computer Speed.6) Explain the benefits of Secondary Storage devices.

How Computer Accepts Input From the Keyboard?

7) What to look while purchasing your own PC?


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How to purchase your own PC / What to look in a PC?

Floppy Drive:

CD-ROM/Writer:

Printer:

Modem:

Transmission Speed

Data Communication

Error Correction

Internal versus External

CPU:Motherboard:

Hard Disk:

Memory or RAM:

Monitor:

Keyboard:

Mouse:

END37 of 37


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Organizing and Accessing Stored Data

Character: A letter, digit, or symbol

Field:set of related characters.E.g.Std Name

Key field:a unique identifierfor a record.

Record: A collection of related fields. E.g. all of

the fields for one studentconstitute one record

File: A collection of related records for university.

Database:A collection of related files stored with

minimum redundancy (duplication).For university,

student file, alumni file, faculty/staff file, courses

file, financial file, etc.

Fil O i ti


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File Organization: Three major methods of organizing datafiles in secondary storage

Sequential File Organization: records must be retrievedin the

Same Physical Sequencein which they are stored.

So the computer must 1st Retrieve Record # 1 then # 2 then # 3 so on.

To update a record, a new sequential file must be created, with

changed and unchanged records

Tape storageuses sequential organization

Indexed File Organization:Combineselements of sequential

and direct methods

Records stored sequentially, but file also contains an index

Index contains record key Data accessed by record key

Direct/Random File Organization:Here the records are notnecessarily stored in sequence.

This method allows to retrievestored data inAny Physical Sequence

without regard to their actual physical order on the storage media.

Magnetic Disk technologyuses the method & is the most popular one.


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Batch Processing:

Transactions collected into groups or

batches.

Processing Stored Data: Transactions processed to update a

master file Transactions:a business event such as asale

Master file:data that is updated when a transactio

occurs, such as asales fileor inventory file

Batch processedand master

file updatedwhen the computer

has few users online

Very efficient use of computer

resources

Master file currentonly

immediately after processing


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Transaction Processing: Processing transactionsas they occur

Also called Real-Time Processing& Online Processing

Terminals must be connected directly to the computer

Offers immediate updatingof master file

End

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Document


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Light source, lens

and diode array

Document

being

scanned

Convertssignals

to numbers

To computer

SCANNER


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Digital Audio Output

[electrical signals](ex. 11100011) to

computer

Analog Sound Signals

Analog Signals are Digitized

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R ti D t


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Representing Data (Cont)

Unit App. Value (bytes) Actual Value (bytes)

Kilobyte (KB) 1,000 1,024 (210

)Megabyte (MB) 1,000,000 1,048,576 (220)

Gigabyte (GB) 1,000,000,000 1,073,741,824 (230)

Terabyte (TB) 1,000,000,000,000 1,099,511,627,776 (240)

November 2007

Fastest Super Computer:NECs SX-9 (Speed upto 839 Teraflops)

Rent:$26,000/Month

November 2007

New Intel Chip for PC:Penrin

New Apple Chip for PC:Leppord

Documents

3 Input Output Devices