It Peripheral

7/31/2019 It Peripheral

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July 5, 2012 1

Computer Peripherals

Represented By :

Chetan S. Shewale (3rd Information Technology)



July 5, 2012 2

Contents

This lecture will discuss: storage devices

input devices and

output devices.



July 5, 2012 3

Introduction

The peripherals are referred to all the items that areexternal to the CPU, main memory and power supply.These includes:

Thumb drive, a floppy disk drive, a hard disk drive, serial ports,parallel port(s), USB ports, a keyboard, a mouse, a network interface, CD-ROM or DVD-ROM drive, a sound system, a modem, amonitor, tape drives, scanners, printers, plotters, and audio, videoinput devices, etc.

Some of the peripherals use the parallel, USB, and serial

ports as their interconnection point to the computer. Others have their own interface to the system bus.



July 5, 2012 4

Introduction

Peripheral devices are classified as storage devices (secondary memory)

Flash memory Magnetic Disk Magnetic tape CD-ROM : (your assignment) Etc.

input devices Keyboard Mouse Touch screen Graphics tablets Etc.

output devices Printers : (your assignment) Scanners Displays Etc.



July 5, 2012 5

Secondary/External Memory

Is treated as I/O. Data and programs in secondary storage must be

copied to primary memory for CPU access.

Except for flash memory, secondary storage issignificantly slower than primary storage, and flashmemory is expensive compared to other forms of secondary storage.

Most secondary storage devices are mechanical innature, and mechanical devices are usually slowerthan devices that are purely electronic.



July 5, 2012 6

Secondary/External Memory

Advantages of secondary storage, Its permanence

The magnetic media used for disk and tape and theoptical media used for disk retain the data

indefinitely. Capable of storing massive amounts of data.

Used for offline archiving, for transferring programsand data from machine to machine, installation

purposes, and for offsite backup storage. Relatively inexpensive compared to main memory.



July 5, 2012 7

Types of Secondary Memory

Flash memory Thumb drive

Magnetic Disk

RAID

Removable

Optical

CD-ROM

CD-Recordable (CD-R) CD-R/W

DVD

Magnetic Tape



July 5, 2012 8

USB flash drives

Typically small, lightweight, removable andrewritable.

Memory capacity typically ranges from 8 MB up to64 GB, limited only by current flash memorydensities.

As capacity increases, so does price.

Several advantages over other portable storage

devices: Generally faster, hold more data, and are considered

more reliable (due to their lack of moving parts) thanfloppy disks.



July 5, 2012 9

USB flash drives

A flash drive has a small PCB encased in a robustplastic or metal casing, making the drive sturdyenough to be carried about in a pocket.

Only the USB connector protrudes from this protection,

and is usually covered by a removable cap.

Most flash drives use a standard type-A USB connectionallowing them to be connected directly to a port on apersonal computer.

Most flash drives are active only when powered bya USB computer connection, and require no otherexternal power source or battery power source.

http://en.wikipedia.org/wiki/Battery_%28electricity%29

http://en.wikipedia.org/wiki/Battery_%28electricity%29



July 5, 2012 10

USB flash drives

The internal components of a typicalflash drive

1 USB connector

2 USB mass storage controller device

3 Test points

4 Flash memory chip

5 Crystal oscillator

6 LED

7 Write-protect switch

8 Unpopulated space for second flashmemory chip



July 5, 2012 11

USB flash drives

The controller contains a small RISC microprocessor and a small amount of on-chipROM and RAM.

Flash storage devices are best compared to othercommon, portable, swappable data storagedevices: floppy disks, Zip disks, and CD-R /CD-RW discs. 3.5 inch floppy disks and Iomega Zip disks.

http://en.wikipedia.org/wiki/RISC

http://en.wikipedia.org/wiki/Read-only_memory

http://en.wikipedia.org/wiki/Random_Access_Memory

http://en.wikipedia.org/wiki/Zip_disk

http://en.wikipedia.org/wiki/CD-R

http://en.wikipedia.org/wiki/CD-RW

http://en.wikipedia.org/wiki/Iomega

http://en.wikipedia.org/wiki/Iomega







http://en.wikipedia.org/wiki/Zip_disk

http://en.wikipedia.org/wiki/Random_Access_Memory

http://en.wikipedia.org/wiki/Read-only_memory

http://en.wikipedia.org/wiki/RISC



July 5, 2012 12

USB flash drives

An obvious extension of flash memory would be asa replacement for hard disks.

Flash memory does not have the mechanical limitationsand latencies of hard drives.

is attractive when considering speed, noise, powerconsumption, and reliability

However, the cost per gigabyte of flash memoryremains significantly higher than that of platter-based hard drives.

http://en.wikipedia.org/wiki/Hard_disk

http://en.wikipedia.org/wiki/Hard_disk



July 5, 2012 13

Magnetic Disk

A magnetic disk consists of one or more flat, circular plattersmade of glass, metal, or plastic, and coated with a magneticsubstance similar to that used on cassette tape.

Substance used to be aluminium

Now glass Improved surface uniformity

Increases reliability

Reduction in surface defects

Reduced read/write errors

Better shock/damage resistance



July 5, 2012 14

Magnetic Disk

There are two major types of magnetic disks, hard disksand floppy disks or diskettes.

The design of a floppy disk limits the number of surfacesto two, specifically the top and bottom of the single disk

platter within its diskette case. Most hard disk drives contain several platters, all mounted

on the same axis, with heads on each surface of eachplatter.



July 5, 2012 15

Magnetic Disk

The heads move in tandem, so they are positioned over thesame point on each surface.

With the head in a particular position, it traces out a circle(track ) on the disk surface as the disk rotates;

Since the heads on each surface all line up, the set of tracks for all the surfaces form a cylinder.

Each track contains one or more blocks of data, whichcommonly divided into equally sized pie shape segments

(sectors). Each sector on a single track contains one block of data,

typically 512 bytes, and represents the smallest unit thatcan be independently read or written.



July 5, 2012 16

Hard Disk Layout



July 5, 2012 17

Disk Data Layout



July 5, 2012 18

Disk Velocity

Bit near centre of rotating disk passes fixed point slowerthan bit on outside of disk

Increase spacing between bits in different tracks

Rotate disk at constant angular velocity (CAV)

Gives pie shaped sectors and concentric tracks Individual tracks and sectors addressable

Move head to given track and wait for given sector

Waste of space on outer tracks

Lower data density

Can use zones to increase capacity

Each zone has fixed bits per track

More complex circuitry



July 5, 2012 19

Disk Layout Methods Diagram

Multiple zone recording - A few high-density disks are designedwith a different number of sectors in different tracks. Thistechnique uses a constant speed motor but compensates fordifferent transfer speeds in the controller.



July 5, 2012 20

Finding Sectors

Must be able to identify start of track and sector Format disk

Additional information not available to user

Marks tracks and sectors



July 5, 2012 21

Winchester Disk FormatSeagate ST506



July 5, 2012 22

Characteristics

Fixed (rare) or movable head Removable or fixed

Single or double (usually) sided

Single or multiple platter Head mechanism

Contact (Floppy)

Fixed gap

Flying (Winchester)



July 5, 2012 23

Fixed/Movable Head Disk

Fixed head One read write head per track

Heads mounted on fixed ridged arm

Movable head

One read write head per side

Mounted on a movable arm



July 5, 2012 24

Removable or Not

Removable disk Can be removed from drive and replaced with another

disk

Provides unlimited storage capacity

Easy data transfer between systems

Nonremovable disk

Permanently mounted in the drive



July 5, 2012 25

Multiple Platter

One head per side Heads are joined and aligned

Aligned tracks on each platter form cylinders

Data is striped by cylinder reduces head movement

Increases speed (transfer rate)



July 5, 2012 26

Multiple Platters



July 5, 2012 27

Tracks and Cylinders



Hard Disk

Hard disk drives are accessed over one of anumber of bus types:

Parallel ATA (PATA, also called IDE or EIDE),

Serial ATA (SATA),

SCSI,

Serial Attached SCSI (SAS), and

Fibre Channel.

Bridge circuitry is sometimes used to connect harddisk drives to buses that they cannot communicatewith natively, such as IEEE 1394 and USB.

July 5, 2012 28



July 5, 2012 29

Floppy Disk

8”, 5.25”, 3.5” Small capacity

Up to 1.44Mbyte (2.88M never popular)

Slow Universal

Cheap

Obsolete?



July 5, 2012 30

Floppy disks vs hard disks

A little difference between the operation of floppydisks and hard disks, but the mechanicaldifferences have important effects on the overallcapacity, speed, data transfer rate, and reliability

of hard drives versus floppy disks. Capacity: hard disk > a floppy disk

The heads on a hard disk do not touch the surface;rather, they ride on a bed of air a few millionths of an

inch above the surface - allows the disk to rotate at highspeed and also allows the designers to locate the tracksvery close together. The result is a disk that can storelarge amounts of data and that retrieves data quickly.



July 5, 2012 31

Floppy disks vs hard disks

Because the floppy disk is soft and flexible, it is necessary to support the disk surface as data is

being read and written.

To do so, the disk is pinched lightly between two heads,

one on each surface of the disk. As a result of this physical contact between the disk

surface and the heads, the disk must be rotated moreslowly, so as not to wear out the heads or scrape the

disk surface. A typical hard disk rotates at 5400 revolutions per

minute (rpm), 7200rpm, or even 10,800rpm.

The floppy disk rotates at 360 rpm.



July 5, 2012 32

Winchester Hard Disk

Developed by IBM in Winchester (USA) The entire assembly is sealed to prevent dirt

particles from wedging between the heads and thedisk platter.

One or more platters (disks)

Heads fly on boundary layer of air as disk spins

Very small head to disk gap

Getting more robust



July 5, 2012 33


Universal Cheap

Fastest external storage

Getting larger all the time 250 Gigabyte now easily available



July 5, 2012 34




July 5, 2012 35

Speed

Seek time The arm first moves the head from its present track until it is

over the desired track.

The average seek time is used as a specification for the disk.

Rotational latency (or rotational delay or latency time)

Once the head is located over the desired track, the read/writeoperation must wait for the disk rotate to the beginning of thecorrect sector.

Speed Rotationalency AverageLat

1

*2

1

For a typical hard disk rotating at 3600 revolutions per minute, or 60revolutions per second, the average latency is: ½ * 1/60 = 8.33msec



July 5, 2012 36

Speed

Access time = Seek + Latency

Transfer time – is the time required to transfer theblock. The transfer time is defined by:

Speed Rotationalctors NumberOfSe *

1Transfer time =

For example, a hard disk rotating at 3600 rpm (or 60 revolutions persecond), with 30 sectors per track. The transfer time for a single block would be: 1/(30*60) =0.55 msec



July 5, 2012 37

BERNOULLI DISK DRIVES

Bernoulli disk drives offer a hybrid approach todisk design that embodies the advantages of bothfloppy disk and hard disk technology.

The disk platter is a 3 1/2” floppy disk housed in a

removable plastic shelled cartridge slightly thickerthan that of a standard floppy disk.

The floppy disk platter spins at about 3000 rpm.

The Bernouffi principle states that a low-pressurelayer is formed next to a surface moving rapidly ina fluid medium such as air.



July 5, 2012 38


The more rapid the surface is moving, the lowerthe pressure.

When not operating, the floppy medium bendsaway from the read/write head.

A cushion of air keeps the head from touching thesurface.

Thus, the Bernoulli cartridge has the advantages

of a hard disk drive, but with the flexibility of aninexpensive, removable cartridge.



July 5, 2012 39


Notice that when something goes wrong, thetendency of the Bernoulli disk is to fall away fromthe head, thus protecting the device from headcrashes.

Because of the design, the Bernoulli drive usesonly one surface and has only a single head.

Example: Zip drives



July 5, 2012 40

Disk Array

In larger computer environments, that provide programand data storage facilities for a network, it is common togroup multiple disks together.

Such a grouping of two or more disk drives is called a disk

array or a drive array. A disk array can be used to reduce overall data access time

by sharing the data among multiple disks and also toincrease system reliability.

The assumption made is that the number of blocks to bemanipulated at a given time is large enough and importantenough.

Example: RAID (Redundant array of inexpensive disks).



July 5, 2012 41

RAID

Redundant Array of Inexpensive Disks (defined byPatterson et al., 1988).

Redundant Array of Independent Disks (industry redefined ‘I’ to be ‘Independent’)

7 levels in common use: RAID 0, RAID 1,….RAID 6 Not a hierarchy but designate different design architecture.

Set of physical disks viewed as single logical drive by O/S

Data distributed across physical drives

Can use redundant capacity to store parity information



July 5, 2012 42

RAID

Two standard methods of implementing a disk array: mirrored array

Has two or more disk drives.

each disk stores exactly the same data.

During reads, alternate blocks of the data are read fromdifferent drives, then combined to reassemble theoriginal data – faster access time.

striped array

requires a minimum of three disk drives.

one disk drive is reserved for error checking. A file segment to be stored is divided into blocks, which

are then written simultaneously to different disks.



July 5, 2012 43

Example: RAID 0

No redundancy Data striped across all disks

Round Robin striping

Increase speed Use in supercomputer where performance and

capacity are important and low cost is moreimportant than reliability.



July 5, 2012 44

Example: RAID 1

Mirrored Disks Data is striped across disks

2 copies of each stripe on separate disks

Read from either Write to both

Recovery is simple

Swap faulty disk & re-mirror

No down time

Expensive



July 5, 2012 45

RAID 0, 1, 2



July 5, 2012 46

Data Mapping For RAID 0



July 5, 2012 47

Magnetic Tape

Serial access Slow

Very cheap

Backup and archive



July 5, 2012 48

MAGNETIC TAPE

Is used for secondary storage:

when offline storage is acceptable or preferred,

when the data storage capacity requirements exceed those of afloppy disk and

when sequential access is adequate.

Tape is nonvolatile, and the data can be stored indefinitely. Modern computers all use tape cartridges for offline storage.

easy to mount and dismount,

and small and easy to store.

Some can store as much as 300GB of compressed data.



July 5, 2012 49

TAPE CARTRIDGE



July 5, 2012 50

DISPLAYS

A computer display (also known as a computer monitor,computer screen, or computer video display) is a device thatcan display signals generated by a computer as images on ascreen.

It is used to display image (or text) to the user.

An image made up of thousands of individual pixels, or

picture elements, arranged to make up a large rectangularscreen.

Each pixel is a tiny square on the display.

A typical screen/display is made up of 768 rows of 1024 pixelseach, known as a 1024 x 768 pixel screen.

Screens of 640 x 480 pixels or 800 x 600 pixels are also still inuse, and resolutions of 1280 x 1024 pixels, or even higherhave become common, especially on physically larger screens.

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Computer



July 5, 2012 51

DISPLAYS

The resolution specifies the minimum identifiable pixel sizecapability of the monitor, therefore, the smaller the numberthe better.

Each individual pixel represents a shade of gray (on amonochrome screen) or a colour.

A color pixel is actually made up of a mixture of differentintensities of red, green, and blue (RGB).

A monochrome scale with no shading would require only 1bit per pixel (‘1’ for white, ‘0’ for black).

Typical colour display has 256 colours, or many more. It takes 1 byte per pixel to represent a 256-clour image.



July 5, 2012 52

DISPLAYS

True colour system use 8 bit per colour (i.e. 24 bitin all).

It can represent 256*256*256 different colours on thescreen.

With 8 bits, there is no way to divide the bits torepresent reds, blues, and greens equally.

Instead, 256 arbitrary combinations of red, blue, andgreen are chosen from a larger palette of colors.

More commonly, a default color scheme is used.



July 5, 2012 53

DISPLAYS

Each pixel value is represented by a value of 0-255,representing the color for that pixel.

A color transformation table, also known as a palette table,holds the RGB values for each of the 256 possible colors.

To display a pixel on the screen, the system transforms thepixel color to a screen color by reading the RGB values thatcorrespond to the particular pixel value from the table - isperformed by a special circuitry on the video card.

Most output, including text data, is presented graphically.



July 5, 2012 54

DISPLAYS

In some PCs, the display circuitry is usuallyprovided on a separate plug-in video card;

video memory is supplied with the card.

In some PCs, and most laptops, the video circuitry

is included on the motherboard.



July 5, 2012 55

DISPLAYS

The actual display is produced by scanning and displaying each

pixel, one row at a time, from left to right, then from top tobottom. Known as a raster scan. Identical to the way that television pictures are generated.

Some monitors Interlace the display, by displaying the odd rows(i.e. row 1, 3, 5 etc.) and then coming back and displaying the

even rows. Not popular - results in flickering that is annoying to some users.

Vector scan - pixels are displayed in whatever order isnecessary to trace out a particular image. E.g. by following the outline of the character vector scan could

trace a character. Not suitable for bit map graphics, but can be used with object

graphics images, such as those used for CAD/CAM applications. Generating vector scan images on a display screen is electronically

much more difficult and expensive than producing raster scans Thus, raster scans are used almost universally today.



July 5, 2012 56

CRT Display Technology

LCD has become more common, but cathoderay tube (CRT) remains the most commondisplay technology.

3 electron guns (red, blue, and green) withinthe tube shoot beams of electrons from the

back of the tube. There is a high voltage applied to the inside of the

face of the tube attracts the beams to the face.



July 5, 2012 57

CRT Display Technology

The face of the tube is painted with tiny dots or thinstripes of phosphors, which glow when struck byelectrons.

A shadow mask in the tube is designed such thatelectrons from each gun can strike only phosphorsof the matching color.

The strength of the beams varies depending on thecolor and brightness of the point being displayed: The stronger the beam for a particular color, the

brighter that color appears on the screen. Monochrome video monitors work identically,

except that only a single gun is required, thephosphor is white, yellow, or green, and no shadowmask is required.

Issues and Problems with Computer Display



July 5, 2012 58

Issues and Problems with Computer Display

Screen burn-in: an image is displayed on thescreen for a long period of time without changing,the screen that is showing will embed itself intothe glass. use a good screensaver program that rotates

often. Some LCD monitors may get "dead pixels" over

time. This generally applies to older LCD monitors

from the 1990's.



July 5, 2012 59

Liquid Crystal Display Technology

A liquid crystal display (LCD) is a thin, flatdisplay device made up of any number of color ormonochrome pixels arrayed in front of a light source or reflector.

it uses very small amounts of electric power, andis therefore suitable for use in battery-poweredelectronic devices.

http://en.wikipedia.org/wiki/Liquid_crystal

http://en.wikipedia.org/wiki/Display_device

http://en.wikipedia.org/wiki/Monochrome

http://en.wikipedia.org/wiki/Pixel

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Electronics

http://en.wikipedia.org/wiki/Electronics

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Pixel

http://en.wikipedia.org/wiki/Monochrome

http://en.wikipedia.org/wiki/Display_device

http://en.wikipedia.org/wiki/Liquid_crystal



July 5, 2012 60

Important factors for LCD

Important factors to consider when evaluating anLCD monitor include:

Resolution:

the physical number of columns and rows of pixels

creating the display (eg, 852x480; 1368x768 etc). viewable size.

response time (sync rate) - amount of time a pixel in anLCD monitor takes to go from active (black) to inactive

(white) and back to active (black) again (ms). Lower numbers mean faster transitions and therefore

fewer visible image artifacts.

http://en.wikipedia.org/wiki/Display_resolution

http://en.wikipedia.org/wiki/Response_time

http://en.wikipedia.org/wiki/Liquid_crystal_display

http://en.wikipedia.org/wiki/Numbers

http://en.wikipedia.org/wiki/Numbers

http://en.wikipedia.org/wiki/Liquid_crystal_display

http://en.wikipedia.org/wiki/Response_time




July 5, 2012 61


matrix type (passive or active): High-resolution color displays such as modern LCD

computer monitors and televisions use an active matrix structure.

Active-matrix displays are much brighter and sharperthan passive-matrix displays of the same size, andgenerally have quicker response times, producing muchbetter images.

Active matrix display: the display panel contains onetransistor for each cell in the matrix.


http://en.wikipedia.org/wiki/Computer_display

http://en.wikipedia.org/wiki/Televisions

http://en.wikipedia.org/wiki/Active-matrix_liquid_crystal_display

http://en.wikipedia.org/wiki/Active-matrix_liquid_crystal_display

http://en.wikipedia.org/wiki/Televisions

http://en.wikipedia.org/wiki/Computer_display




July 5, 2012 62


viewing angle. color support

brightness and contrast ratio, aspect ratio, andinput ports (e.g. DVI or VGA ).

http://en.wikipedia.org/wiki/Contrast_%28vision%29

http://en.wikipedia.org/wiki/Digital_Visual_Interface

http://en.wikipedia.org/wiki/Video_Graphics_Array


http://en.wikipedia.org/wiki/Digital_Visual_Interface

http://en.wikipedia.org/wiki/Contrast_%28vision%29



July 5, 2012 63

LCD DISPLAYS

LCD panels have the advantage of: small size,

bright images,

no flicker, and

low power consumption.

so they are ideal for laptop computers.



July 5, 2012 64

COMPUTER DISPLAY STANDARD

Videostandard

Description

MDA Monochrome Display Adapter, the original standard on IBMPCs and IBM PC XTs with 4 KB video RAM. Introduced in1981 by IBM. Supports text mode only.

CGA Color Graphics Adapter. Introduced in 1981 by IBM, as thefirst color display standard for the IBM PC. The standardCGA graphics cards were equipped with 16 KB videoRAM.

http://en.wikipedia.org/wiki/IBM_PC

http://en.wikipedia.org/wiki/IBM_PC_XT

http://en.wikipedia.org/wiki/Kilobyte

http://en.wikipedia.org/wiki/Video_RAM

http://en.wikipedia.org/wiki/1981


http://en.wikipedia.org/wiki/International_Business_Machines


http://en.wikipedia.org/wiki/Text_mode









http://en.wikipedia.org/wiki/Color_Graphics_Adapter




http://en.wikipedia.org/wiki/Video_RAM

http://en.wikipedia.org/wiki/Kilobyte

http://en.wikipedia.org/wiki/IBM_PC_XT



http://en.wikipedia.org/wiki/Monochrome_Display_Adapter



July 5, 2012 65


Videostandard

Description

EGA Enhanced Graphics Adapter. Introduced in 1984 by IBM. Aresolution of 640 × 350 pixels of 16 different colors (4 bits perpixel, or bpp ).

VGA Video Graphics Array, introduced in 1987 by IBM. VGA is

actually a set of different resolutions, but is most commonlyused today to refer to 640 × 480 pixel displays with 16 colors (4bits per pixel).

SVGA Super VGA, a video display standard created by VESA for IBMPC compatible personal computers. Introduced in 1989.

XGA Extended Graphics Array is an IBM display standard introducedin 1990. XGA-2 added 1024 × 768 support for high color andhigher refresh rates, improved performance, and support for1360 × 1024 in 16 colors (4 bits per pixel).

The Video Electronics Standards Association (VESA) is an international body, founded

by NEC Home Electronics and eight other video display adapter manufacturers.

http://en.wikipedia.org/wiki/NEC_Corporation

http://en.wikipedia.org/wiki/Enhanced_Graphics_Adapter







http://en.wikipedia.org/wiki/XGA


http://en.wikipedia.org/wiki/VESA

http://en.wikipedia.org/wiki/Super_Video_Graphics_Array




http://en.wikipedia.org/wiki/Enhanced_Graphics_Adapter



July 5, 2012 66


Videostandard

Description

SXGA Super XGA, a widely used de facto 32 bit Truecolor standard. The resolution: 1280×1024

UXGA Ultra XGA is a de facto Truecolor standard. Theresolution: 1600×1200

WUXGA Widescreen Ultra Extended Graphics Array is aversion of the UXGA format. This display is becomingpopular in high end 15" and 17" widescreen notebookcomputers. The resolution: 1920X1200.

http://en.wikipedia.org/wiki/WUXGA

http://en.wikipedia.org/wiki/Truecolor

http://en.wikipedia.org/wiki/De_facto

http://en.wikipedia.org/wiki/UXGA

http://en.wikipedia.org/wiki/Truecolor

http://en.wikipedia.org/wiki/De_facto

http://en.wikipedia.org/wiki/SXGA



July 5, 2012 67

Computer Display Standard

Video

standard

Description

WQXGA Widescreen Quad Extended Graphics Array is a version ofthe XGA format. This display is becoming popular in somerecent desktop monitors. The resolution: 2560x1600.

WXGA Widescreen Extended Graphics Array is a version of theXGA format. This display is becoming popular in somerecent notebook computers. The resolution: 1280x720.

WSXGA, orWXGA+ Widescreen Extended Graphics Array PLUS is a versionof the WXGA format. This display aspect ratio is becomingpopular in some recent notebook computers. Theresolution: 1440x900.

http://en.wikipedia.org/wiki/WSXGA_Wide_XGA_PLUS


http://en.wikipedia.org/wiki/Aspect_ratio_(image)

http://en.wikipedia.org/wiki/Aspect_ratio_(image)



http://en.wikipedia.org/wiki/Wide_XGA

http://en.wikipedia.org/wiki/WQXGA



July 5, 2012 68

Scanners

Primary used - to input paper images. A device that analyzes an image or an object (such

as an ornament) and converts it to a digital image.

Scanners are generally less expensive and moreconvenient.

3 primary types of scanners:

flatbed scanners,

sheet-fed scanners, handheld scanners,

but all 3 work similarly and differ only in the way the scanelement is moved with respect to the paper.



July 5, 2012 69

Scanners

In a flatbed scanner, the paper is placed on aglass window, while the scan element moves downthe page, much like a copy machine.

In a sheet-fed scanner, a single page of paper is

propelled through the mechanism with rollers; thescan element is stationary.

Handheld scanners are propelled by the user over

the page.



July 5, 2012 70

Scanners

The scanning mechanism consists of a light sourceand a row of light sensors.

As the light is reflected from individual points on thepage, it is received by the light sensors and translated

to digital signals that correspond to the brightness of each point.

Color filters can be used to produce color images.

The resolution of scanners is approximately 600 —

2400 points per inch.



July 5, 2012 71

User Input Devices

Users use a variety of devices to interact with thecomputer:

Text Input:

Keyboards (most popular) - consist of a number of

switches and a keyboard controller. The keyboardcontroller is built into the keyboard itself.

Speech recognition.

Pointing devices:

Mouse- a handheld pointing device, designed to situnder one hand of the user and to detect movementrelative to its two-dimensional supporting surface.

mechanical mouse

http://en.wikipedia.org/wiki/Pointing_device

http://en.wikipedia.org/wiki/Pointing_device



July 5, 2012 72

Pointing devices

Optical mouse uses a light-emitting diode andphotodiodes to detect the movement of theunderlying surface, rather than moving some of itsparts as in a mechanical mouse.

Laser mouse uses a small laser instead of a LED.

http://en.wikipedia.org/wiki/Light-emitting_diode

http://en.wikipedia.org/wiki/Photodiode

http://en.wikipedia.org/wiki/Laser

http://en.wikipedia.org/wiki/Laser

http://en.wikipedia.org/wiki/Photodiode






July 5, 2012 73

USER INPUT DEVICES

Operating a mechanical mouse. 1: Moving the mouse turns the ball.2: X and Y rollers grip the ball andtransfer movement.3: Optical encoding disks includelight holes.

4: Infrared LEDs shine through thedisks.5: Sensors gather light pulses toconvert to X and Y velocities. .

d





July 5, 2012 74

Pointing devices

Joystick

Touch screen

Touchpad

Light pen- pointed at the screen to identify a

position on the screen. By moving the pen aroundthe screen, a cursor can be made to follow thepen.

Graphics tablet.

Image, video and audio input devices



July 5, 2012 75

Image, video and audio input devices

Image scanner

3D scanner

Digital camera

Webcam

Digital video recorder

Digital camcoder

Digital audio recorder microphone



July 5, 2012 76

Communication Devices

Like other I/O devices, there is a network interface unit

(NIU) that handles the physical characteristics of theconnection and one or more I/O drivers that manage andsteer input data, output data, and interrupts.

The interface between a computer and a network is more

complicated than that for most other I/O peripherals. Data must be formatted in specific ways to communicate

successfully with a wide range of application and system softwarelocated on other computers.

The computer also must be able to address a large number of devices individually, specifically, every other computer connected to

the network. Security of communication is important.



July 5, 2012 77

Communication Devices

Most of these concerns are handled with protocolsoftware in the operating system.

The NIU is responsible only for:

the electrical signals that connect the computer to the

network, either directly or through a communicationchannel, and

for the protocols, implemented in hardware, that definethe specific rules of communication for the network.

These protocols are called medium access controlprotocols, or MACs.



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It Peripheral

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