Chapter 7 Storage

TE-102 Introduction to Computinghttp://web.uettaxila.edu.pk/CMS/UG/TE-102/

Chapter 7 Objectives

Discuss the various types of items that users store on computer media

Discuss the various types of items that users store on computer media

Differentiate between storage devicesand storage media

Differentiate between storage devicesand storage media

Describe the characteristics ofa floppy disk drive

Describe the characteristics ofa floppy disk drive

Identify the uses of Zip disksIdentify the uses of Zip disks

Describe the characteristics ofa hard disk

Describe the characteristics ofa hard disk

Identify the advantages of usingan Internet hard drive

Identify the advantages of usingan Internet hard drive

Describe the characteristics ofCDs and DVDs

Describe the characteristics ofCDs and DVDs

Differentiate among CD-ROMs,CD-RWs, DVD-ROMs, and DVD+RWs

Differentiate among CD-ROMs,CD-RWs, DVD-ROMs, and DVD+RWs

Identify the uses of tapeIdentify the uses of tape

Discuss PC Cards and the various typesof miniature storage media

Discuss PC Cards and the various typesof miniature storage media

Identify uses of microfilm and microfiche

Identify uses of microfilm and microfiche

Next

Storage

What is storage?

p. 7.02 Fig. 7-1 Next

Holds data, instructions, and information for future use Storage medium is physical material used for storage

Also called secondary storage

Floppy disk

microfiche

Miniatgure mobile storage media

Zip disk

PC card

Internal hard disk

External hard disk

Removable hard disk

tape

CD or DVD

Storage

What is capacity?

p. 7.04 Next

Kilobyte (KB) 1 thousand

Megabyte (MB) 1 million

Gigabyte (GB) 1 billion

Terabyte (TB) 1 trillion

Petabyte (PB) 1 quadrillion

Number of bytes (characters) a storage medium can hold

Exabyte (EB) 1 quintillion

Storage Medium(floppy disks, Zip disks,

hard disks, CDs)

Storage

How does volatility compare?

p. 7.04 Next

No

nvo

lati

le

Storage medium is nonvolatile—contents retained when power is off

Contents Contents retainedretained

Contents Contents available to useravailable to user

Memory(most RAM)

(chips on motherboard)

Screen Display

ON OFF

Vo

lati

le Display Display disappearsdisappears

Data andData andinstructions instructions

available to useravailable to user

Display Display appearsappears

Data and Data and instructions erasedinstructions erased

Memory is volatile—holds data and instructions temporarily

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

WritingWritingProcess of transferring Process of transferring

items from memory items from memory to storage mediato storage media

Storage

What is a storage device?

p. 7.04 Next

ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

ReadingReadingProcess of transferring Process of transferring

items from storage items from storage media to memorymedia to memory

Hardware that Hardware that records and records and

retrieves items retrieves items to and from to and from

storage mediastorage media

Functions as source of input

Creates output

Floppy Disk Small files to be transported

Secondary Storage

Primary Storage

Hard Disk

CDs and DVDs

Miniature Storage Media

Tape

Items waiting to be interpretedand executed by the processor

Operating system, applicationsoftware, user data and information

Software, backups, movies, music

Digital pictures or small files tobe transported

Backups

Memory (most RAM)

Stores …

Storage

What is access time?

p. 7.04

Time it takes storage device to locate item on storage medium

Next

Time required to deliver item from memory to processor

fastertransfer

rates

slowertransfer

rates

Floppy Disks

What is a floppy disk?

p. 7.05 Fig. 7-5 Next

Portable, inexpensive storage medium (also called diskette)

Thin, circular, flexible film enclosedin 3.5” wide plastic shell

shutter

shell

liner

magneticcoating

flexible thin film

metal hub

Floppy Disks

What is a floppy disk drive?

p. 7.06 Fig. 7-6 Next

Floppy disk drive built intoa desktop computer

External floppy disk drive attaches toa computer with a cable

Also called secondary storage

One floppy drive, named drive A If two floppy drives, second

designated as drive B

Device that reads from andwrites to floppy disk

Floppy Disks

How does a floppy disk drive work?

p. 7.06 Fig. 7-7 Next

Step 1. When you insert the floppy disk into drive, shutter moves to the side to expose the recording surface on disk.

Step 2. When you initiate a disk access, circuit board on drive that contains electronics sends signals to control movement of read/write heads until they barely touch surface (film) inside floppy disk’s shell.

Step 3. For write instructions, circuit board verifies whether or not disk can be written on.Step 4. Motor spins

a shaft, which causes surface inside floppy disk’s shell to spin.

Step 5. Motor positions read/write heads over correct location on recording surface of disk.

Step 6. Read/write heads read data from and write data on floppy disk.

Floppy Disks

p. 7.07 Fig. 7-8 Next

What are tracks and sectors?

Trackis narrow

recording bandthat forms fullcircle on disk

Sector stores up to512 bytes

of data

Formatting prepares disk for use and marks bad sectors as unusable

Click to view Web Link,then click Floppy Disksbelow Chapter 7

Floppy Disks

How do you compute a disk’s storage capacity?

p. 7.08 Next

Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector For high-density disk: 2 sides 80 tracks 18 sectors per track 512 bytes

per sector = 1,474,560 bytes

Characteristics of a3.5-inch High-DensityFloppy Disk

Capacity: 1.44 MB

Sides: 2

Tracks: 80

Sectors per track: 18

Bytes per sector: 512

Sectors per disk: 2880

Floppy Disks

p. 7.08 Next

Never open theshutter and

touch the disk’ssurface

Never open theshutter and

touch the disk’ssurface

How do you care for a floppy?

Avoid exposureto heat and

cold

Avoid exposureto heat and

coldAvoid exposure

to magneticfields

Avoid exposureto magnetic

fields Avoid exposureto contaminants

such as dust,smoke, or

salt air

Avoid exposureto contaminants

such as dust,smoke, or

salt airKeep disks ina storage tray

when notusing them

Keep disks ina storage tray

when notusing them

Proper care helps maximize disk’s life Floppy disk can last at least seven years

Floppy Disks

What is a write-protect notch?

p. 7.08 Fig. 7-10 Next

Small opening with a cover that you slide Protects floppy disk from being erased accidentally

hole on thisside meansdisk is high

density

hole on thisside meansdisk is high

density

write-protected

not write-protected

notch closedmeans you

can write onthe disk

notch closedmeans you

can write onthe disk

notch openmeans you

cannot writeon the disk

notch openmeans you

cannot writeon the disk

ExternalZip drive

Zip® Disks

What is a Zip disk?

p. 7.09 Fig. 7-11 Next

Magnetic medium that stores from 100 MB to 750 MB of data

Zip disks require a Zip drivec—chigh capacity drive that reads from and writes on a Zip disk Built-in Zip drive External Zip drive : connects to

a USB, FireWire or parallel port

Used to back up and to transfer files Backup is duplicate of file, program, or disk

in case original is lostc

Zip disk

Hard Disks

What is a hard disk?

p. 7.09 Fig. 7-12 Next

hard disk installedin system unit

High-capacity storage ( 40 to 250 GB and more)

Consists of several inflexible, circular platters that store items electronically

Components enclosed in airtight, sealed case for protection

Sometimes called a fixed disk because it is

mounted in a drive bay and usually is not potable

Hard Disks

What are characteristics of a hard disk?

p. 7.10 Fig. 7-13 Next

The capacity of a hard disk is determined from the number of platters it contains, together withcomposition of themagnetic coating on the platters.

Hard Disks

How does a hard disk work?

p. 7.11 Fig. 7-14 Next

Step 1.Circuit board controls movement of head actuator and a small motor.

Step 2.Small motor spins platters while computer is running.

Step 3.When software requests a disk access, read/write heads determine current or new location of data.

Step 4.Head actuator positions read/write head arms over correct location on platters to read or write data.

Hard Disks

What is a cylinder?

p. 7.11 Fig. 7-15 Next

Vertical section of track through all platters

Single movement of read/write head arms accesses all plattersin cylinder

platter

read/writehead

platter

sides

cylinder

track

sector

Hard Disks

What is a head crash?

p. 7.12 Fig. 7-16 Next

clearance

read/write head

platter

hair

dustsmoke

Spinning creates cushion of air that floats read/write head above platter

Head crash results in a loss of data or sometimes loss of the entire drive - Needs to backup the hard disk regularly.

Occurs when read/write head touches platter surface

A smoke particle, dust particle, or human hair could render drive unusable

Clearance between head and platter is approximately two-millionths of an inch

Hard Disks

Hard disk access time can be improved by using disk caching.

Two types of cache : memory cache and disk cache. Memory cache: used to improve the memory access

time. L1 and L2 cache for most PC, L3 cache for server. L1 and L2 are built directly on to the processor chip. Search order: L1, then L2, then L3 (if it exists), then RAM

Disk cache: used to improve the hard disk access time

hard disk

Next

Hard Disks

What is a disk cache?

p. 7.12 Fig. 7-17

Portion of memory that processor uses to store frequently accessed items

second requestfor data—to hard disk

disk cache

first requestfor data—to disk cache

processor

Hard Disks

What are external hard disks and removable hard disks?

p. 7.13 Fig. 7-18 Next

External hard disk—freestandinghard disk that connects with a cable to a USB, FireWire or other port on the system unit. Storage capacities up to 250 GB or higher

Used to back up or transfer files

Removable hard disk—hard diskthat you insert and removefrom hard disk driveStorage capacities up to 80 GB or higher

Hard Disks

What is a disk controller?

p. 7.13 Next

EIDEEIDE (EEnhancednhanced IIntegratedntegrated DDrive rive EElectronics) controller supports four lectronics) controller supports four hard disks, provides connections for hard disks, provides connections for

CD and DVD drivesCD and DVD drives

Chip and circuits that Chip and circuits that control transfer of control transfer of items from diskitems from disk

SCSISCSI((SSmallmall CComputeromputer SSystemystem IInterface)nterface)

controller supports up to fifteencontroller supports up to fifteendevices including hard disks, CDdevices including hard disks, CD

and DVD drives, tape drives, printers,and DVD drives, tape drives, printers,scanners, network cardsscanners, network cards

Hard Disks

What is an Internet hard drive (online storage)?

p. 7.14 Fig. 7-19 Next

Others can be authorized to access your data

Service on Web that provides storage for minimal monthly fee

Files can be accessed from any computer with Web access

Large files can be downloaded instantaneously

Click to view Web Link,then click Hard Drivesbelow Chapter 7

Push the same buttonto close the tray.

CDs and DVDs

What are CDs and DVDs?

p. 7.15 Fig. 7-20 Next

Most PCs include CD or DVD drive, most play audio CDs

Flat, round, portable metal discs with protective plastic coating

These are optical media that store items by using microscopic pits and lands

Insert the disc,label side up.

Push the button toslide out the tray.

CDs and DVDs

How does a laser read data on a CD or DVD?

p. 7.16 Fig. 7-21 Next

laserdiode

laserdiode

prism prism

light-sensingdiode

light-sensingdiode

0 1

lens lenspit land

disc label

Step 1.Laser diode shines a light beam towarddisc.

Step 2.If light strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode.

Step 3.Reflected light is deflected to alight-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.

CDs and DVDs

How is data stored on a CD or DVD?

p. 7.16 Fig. 7-22 Next

Typically stored in single track

Track divided into evenly sized sectors that store items

single trackspirals to edgeof disc

disc sectors

CDs and DVDs

How should you care for a CD or DVD?

p. 7.16 Fig. 7-23 Next

Do store thedisc in a jewelbox whennot in use

Do hold a discby its edges

Do noteat, smoke, ordrink neara disc

Do not stack discs

Do not exposethe disc to excessiveheat or sunlight

Do not touchthe undersideof the disc

CDs and DVDs

What is a CD-ROM?

p. 7.17 Fig. 7-24 Next

Compact disc read-only memory A type of optical disc that uses laser technology to store data.

Cannot erase or modify contents. Called a single-session disc because manufactures write all items on the disc at one time. Typically holds 650 MB to 1 GB. Commonly used to distribute

multimedia and complex software (Encyclopedias, games…)

CDs and DVDs

The speed of a CD-ROM drive determines how fast the

drive installs program and accesses the disc. Original CD-ROM drives: single speed drives with

transfer rates of 150 KBps (Kilobytes per second). To measure the transfer rate, manufacturers use the

relative values of the transfer rate of this original CD-

ROM drives They use an X to denote the original transfer rate of 150

KBps.

What is the data transfer rate of a CD-ROM drive?

CDs and DVDs

What is the data transfer rate of a CD-ROM drive?

p. 7.18 Next

75X

Ranges from 48X to 75X

or faster

75 75 150 KBps = 11,250 KBps 150 KBps = 11,250 KBps 48X: 48X:

48 48 150 KBps = 7,200 KBps 150 KBps = 7,200 KBps

CDs and DVDs

What is a Picture CD?

p. 7.19 Fig. 7-25 Next

Film developers offer

Picture CD service

Can be modified

using photo editing software

A type of CD that stores digital versions of

roll of film using a jpg file format

Step 3.At home, print images from Picture CD with your ink-jet photo printer.

At a store, print images from Picture CD at kiosk.

Step 1.Drop off film to be developed. Mark the Picture CD box on the film-processing envelope.

Step 2.When you pick up prints and negatives, a Picture CD contains digital images of each photograph.

CDs and DVDs

What is a PhotoCD?

Another type of CD that stores digital photographic images. A single PhotoCD stores images from multiple rolls of

film using the Image Pac, or PCD, file format developed

by Kodak. Designed for commercial and professional users. Available in many resolutions, ranging from 128 x 192

to 4096 x 6411 pixels. A PhotoCD is a multisession disc; users can save

additional photos on the disc at a later time.

CDs and DVDs

What is a CD-R (compact disc-recordable)?

Multi-session CD with which users write on part of the disc at one time and another part at a later time. Disc’s contents cannot be erased. Most current CD-ROM drives can read a CD-R. CD-R drives can read both audio CDs and standard CD-ROMs. Speed of CD-R drive

Reading speed: 48X or more Writing speed: 40X or more Manufactures list the writing speed first and reading speed next, such as 40/48.

Slightly more expensive than standard CD-ROM drives.

CDs and DVDs

What is a CD-RW (compact disc-rewritable)? Erasable disc users can write on multiple times. CD-RW overcomes the major disadvantage of CD-R disc. With CD-RW, the disc acts like a floppy disk or hard disk, allowing users to write and rewrite data onto it multiple times. Reliability of disc tends to drop with each successive rewrite. Speed of CD-RW drive

writing speed: 52X or more rewriting speed: 24X or more reading speed: 52X or more Manufacturers state the speeds in the above order: 52/24/52.

Multithread CD drive is a drive that reads audio CDs, data CDs, CD-Rs, and CD-RWs. Most current CD drives are multithread.

CDs and DVDs

Comparison of CD-ROM, CD-R and CD-RW

p. 7.20

Must haveCD recorder

or CD-R drive

CD-R (compact disc-recordable)— multi-session CD

CD-RW (compact disc-rewritable)—ceerasable disc you can write on

multiple times Must haveCD-RW softwareand CD-RW drive

CD-ROM (compact disc read only memory)— single-session CD Must have

CD-ROM drive

How is an audio CD created?

Step 5.User listensto song ona personal computer or removes CD and listens to song ona portable CD player.

Step 2.Song is stored on audio CD andpurchasedby user.

Step 1.Artist composes a song.

Step 3.User inserts audio CD into CD drive, plays song, and rips desired tracks onto hard disk.

Step 4.User copies file to aCD-RW disc.

Nextp. 7.20 Fig. 7-26

CDs and DVDs

From a purchased CD. . .

CDs and DVDs

Step 3.User pays for and downloads song as audio file onto a hard disk.

Step 2.Song is compressed and stored on the Internet.

How is an audio CD created? From the Internet. . .

p. 7.20 Fig. 7-26 Next

Step 5.User listensto song ona personal computer or removes CD and listens to song ona portable CD player.

Step 1.Artist composes a song.

Step 4.User copies file to aCD-RW disc.

CDs and DVDs

What is a DVD-ROM (digital versatile disc-ROM or digital video disc-ROM)?

p. 7.22 Fig. 7-27 Next

DVD

DVD drive

High capacity disc capable of storing 4.7 GB to 17 GB

Must have DVD-ROM drive or DVD player to read DVD-ROM

Newer DVD-ROM drive, CD-RW/DVD, can read audio CDs, CD-ROMs, CD-Rs, and CD-RWs

Stores databases, music, complex software, and movies

CDs and DVDs

How does a DVD-ROM store data?

DVD-ROM uses one of three storage techniques Make the disc denser by packing the pits closer

together. Two layers of pits are used, lower layer is

semitransparent so laser can read through Some are double-sided

DVD-ROM Storage Capacities

Sides Layers Storage Capacity

1 1 47 GB

1 1 8.5 GB

2 1 9.4 GB

2 2 17 GB

CDs and DVDs

DVD Variations

DVD-R (DVD-recordable) DVD+RW (DVD-rewritable) DVD+RAM (DVD+random access memory) : allow users to erase and record on a DVD+RAM discs more than 100,000 times. Storage capacity up to 4.7 GB per side

Tape

What is tape?

p. 7.24 Fig. 7-29 Next

Magnetically coated plastic ribboncapable of storing large amountsof data at low cost

Primarily used for backup Tape drive reads and writes data on a tape

Tape drive

Tape cartridge

Tape

How is data stored on a tape? Sequential access

Digital audio tape DAT 2 GB to 240 GB

(also called digital data storage) (also called DDS)

Digital linear tape DLT 20 GB to 229 GB

Linear tape-open LTO 100 GB to 200 GB

Quarter-inch cartridge QIC 40 MB to 25 GB

Travan TR 8 GB to 40 GB

Popular Types of Tape

Name Abbreviation Storage Capacity

Unlike direct access (random access) — used on floppy disks, Zip disks, hard disks, CDs, and DVDs — which can locate particular item immediately

Reads and writes data consecutively, like music tape

PC Cards

What is a PC Card?

p. 7.24 Figs. 7-31–7-32 Next

PC Cards

Category Thickness Use

Type I 3.3 mm RAM, SRAM, flash

memory

Type II 5.0 mm Modem, LAN, SCSI,

sound, TV turner, hard

disk, or other storage

Type III 10.5 mm Rotating storage such

as a hard disk

Adds capabilities to computer Credit-card-sized device commonly

used in notebook computers

Miniature Mobile Storage Media

What is miniature mobile storage media?

p. 7.25 Fig. 7-33 Next

Storage for small mobile devices

Miniaturemobile storage

media

Miniature Mobile Storage Media

What are common types of miniature mobile storage media? (Refer to the Figure 7-34 for storage capacity and use)

Next

Smart Media Secure Digital

Microdrive ™ USBDrive™Memory Stick ®

CompactFlash

Miniature Mobile Storage Media

p. 7.27 Fig. 7-35 Next

What is a card reader? Reads information stored on miniature mobile storage media Type of card determines type of card reader needed

Miniature Mobile Storage Media

What is a USB flash drive (keychain drive)?

Flash memory storage device that plugs into a USB port on a computer or potable device Storage capacity is up to 32 GB Data transfer rate is about 16 MBps

Miniature Mobile Storage Media

What is a smart card?

p. 7.27 Fig. 7-36 Next

Stores data on microprocessor embedded in small card

Difference with a flash memory card: Flash memory card has only

storage capabilities. Smart card contains a

processor and have input, process, output, and storage capabilities

Sometimes called intelligent smart card

Miniature Mobile Storage Media

Where is a smart card used?

To store a prepaid dollar amount, as in a prepaid telephone calling card or electronic money To store medical records, vaccination data, and other health- care information To track information such as customer purchases or employee attendance

Miniature Mobile Storage Media

What is e-money (electronic money)?

p. 7.28 Next

Sometimes placed Sometimes placed on smart cardon smart card

Means of paying forMeans of paying forgoods and servicesgoods and services

over the Internetover the InternetAlso called digital cashAlso called digital cash

Bank issues unique Bank issues unique digital cash numbers digital cash numbers that represent amount that represent amount of moneyof money

Money is withdrawn Money is withdrawn from your bank from your bank accountaccount

Microfilm and Microfiche

What are microfilm and microfiche?

p. 7.28 Fig. 7-37 Next

Images recorded using Images recorded using computer output microfilm recordercomputer output microfilm recorder

Store microscopic images of Store microscopic images of documents on roll or sheet of filmdocuments on roll or sheet of film

Microfilm — 100- to215-foot roll of film

Microfiche — small sheet of film, usually 4” 6”

Microfilm and Microfiche

Applications?

Libraries use to store back issues of newspapers, magazines, and genealogy records Large organizations use to archive inactive files Banks use to store transactions and canceled checks US Army uses to store personnel records

Advantages?

Reduce the amount of paper usage Inexpensive Have the longest life of any storage media

Microfilm and Microfiche

How do life expectancies of various media compare?

p. 7.29 Fig. 7-38 Next

Media Life Expectancies

Magnetic disks 3 to 5 years 20 to 30 years

CDs and DVDs discs 5 to 10 years 50 to 100 years

Microfilm 100 years 500 years

Media Type Guaranteed Life Potential LifeExpectancy Expectancy

Microfilm and microfiche have longest life of any storage media

Putting It All Together

What are recommended storage devices for home users?

p. 7.29 Fig. 7-39 Next

Home

3.5-inch high-density floppy disk drive

250 MB Zip drive 60 GB hard disk Internet hard drive CD or DVD drive Card reader

Putting It All Together

What are recommended storage devices for small office/home office (SOHO) users?

p. 7.29 Fig. 7-39 Next

3.5-inch high-density floppy disk drive

250 MB Zip drive 100 GB hard disk Internet hard drive CD or DVD drive External hard drive for backupSmall Office/

Home Office (SOHO)

Putting It All Together

What are recommended storage devices for mobile users?

p. 7.29 Fig. 7-39 Next

3.5-inch high-density floppy disk drive 2 GB PC Card hard disk or USB Drive 40 GB hard disk Internet hard drive CD or DVD drive Card reader External or removable hard disk for

backupMobile

Putting It All Together

What are recommended storage devices for large business users?

p. 7.29 Fig. 7-39 Next

3.5-inch high-density floppy disk drive

160 GB hard disk CD or DVD drive Microfilm or microfiche Smart card reader Tape driveLarge Business

Putting It All Together

What are recommended storage devices for power users?

p. 7.29 Fig. 7-39 Next

3.5-inch high-density floppy disk drive CD or DVD drive 160 GB hard disk Internet hard drive External or removable hard disk for

backup

Power

Summary of Storage

Floppy disksFloppy disks

Zip disksZip disks

Internal hard disksInternal hard disks

External hard disksExternal hard disks

Removable hard disksRemovable hard disks

CD-ROMsCD-ROMs

CD-RWsCD-RWs

DVD-ROMsDVD-ROMs

DVD+RWsDVD+RWs

TapeTape

PC CardsPC Cards

Flash memory cards and other miniature mobile storage media

Flash memory cards and other miniature mobile storage media

Microfilm and microficheMicrofilm and microfiche

Chapter 7 Complete