Chapter 7 Storage

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Chapter 7Storage
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Chapter 7 Objectives
Differentiate between storage devicesand storage
media
Differentiate among CD-ROMs,recordable CDs,
rewritable CDs, DVD-ROMs, recordable DVDs, and
rewritable DVDs
Describe the characteristics ofmagnetic disks
Identify the uses of tape
Differentiate between floppy disks and Zip disks
Discuss PC Cards and the various typesof
miniature mobile storage media
Describe the characteristics ofa hard disk
Identify uses of microfilm and microfiche
Describe the characteristics of optical discs
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Storage

• What is storage?

• Holds data, instructions, and information for
  future use

• Storage medium is physical material used for
  storage

• Also called secondary storage

p. 354 Fig. 7-1
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Storage

• What is capacity?

• Number of bytes (characters) a storage medium can
  hold

p. 356
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Storage

• How does volatility compare?

• Storage medium is nonvolatilecontents retained
  when power is off

• Memory is volatileholds data and instructions
  temporarily

ON
OFF
Display disappears
Display appears
Volatile
Data andinstructions available to user
Data and instructions erased
Contents retained
Contents available to user
Nonvolatile
p. 356
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Storage

• What is a storage device?

Hardware that records and retrieves items to
and from storage media
Writing Process of transferring items from
memory to storage media
Reading Process of transferring items from
storage media to memory
p. 356
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Storage

• What is access time?

• Time it takes storage device to locate item on
  storage medium

• Time required to deliver item from memory to
  processor

fastertransferrates
slowertransferrates
p. 357 Fig. 7-4
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Magnetic Disks

• What are tracks and sectors?

Formatting prepares disk for use and marks bad
sectors as unusable
p. 357 Fig. 7-5
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Magnetic Disks

• What is a floppy disk?

shutter

• Portable, inexpensive storage medium (also called
  diskette)

shell
liner
magneticcoating
Thin, circular, flexible film enclosedin 3.5
wide plastic shell
metal hub
flexible thin film
p. 358
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Magnetic Disks

• What is a floppy disk drive?

• Device that reads from andwrites to floppy disk

Floppy disk drive built intoa desktop computer

• One floppy drive, named drive A

• Also called secondary storage

External floppy disk drive attaches toa computer
with a cable
p. 358 Fig. 7-6
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Magnetic Disks

• How do you compute a disks storage capacity?

• 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
p. 359
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Magnetic Disks

• What is a write-protect notch?

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

p. 359 Fig. 7-7
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Magnetic Disks

• What is a Zip disk?

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

• Used to back up and to transfer files

• Backup is duplicate of file, program, or disk in
  case original is lost

• Zip disks require a Zip drivecchigh capacity
  drive that reads from and writes on a Zip disk

c
p. 359 Fig. 7-9
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Magnetic Disks
hard disk installedin system unit

• What is a hard disk?

• High-capacity storage

• Consists of several inflexible, circular platters
  that store items electronically

• Components enclosed in airtight, sealed case for
  protection

p. 360 Fig. 7-10
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Magnetic Disks

• What are characteristics of a hard disk?

actualdiskcapacity
p. 361 Fig. 7-11
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Magnetic Disks

• How does a hard disk work?

Step 3.When software requests a disk access,
read/write heads determine current or new
location of data.
Step 2.Small motor spins platters while computer
is running.
Step 4.Head actuator positions read/write head
arms over correct location on platters to read or
write data.
Step 1.Circuit board controls movement of head
actuator and a small motor.
p. 361 Fig. 7-12
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Video Install a New Hard Drive
Speed up your computer with a new hard drive
low quality(click to start)
high quality(click to start)
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Magnetic Disks
platter

• What is a cylinder?

track

• Vertical section of track through all platters

sector

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

read/writehead
platter
sides
p. 362 Fig. 7-13
cylinder
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Magnetic Disks

• What is a head crash?

• Occurs when read/write head touches platter
  surface

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

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

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

hair
read/write head
dust
clearance
smoke
platter
p. 362 Fig. 7-14
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Magnetic Disks

• What is a disk cache?

• Portion of memory that processor uses to store
  frequently accessed items

p. 363 Fig. 7-15
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Magnetic Disks

• What is a miniature hard disk?

• Provide users with greater storage capacities
  than flash memory
• Some have a form factor of less than 1 inch
• Storage capacities range from 2 GB to 100 GB

p. 363 Fig. 7-16
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Magnetic Disks

• What are external hard disks and removable hard
  disks?

• Used to back up or transfer files

Removable hard diskhard diskthat you insert and
removefrom hard disk drive
External hard diskfreestandinghard disk that
connects to system unit
p. 364 Fig. 7-17
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Magnetic Disks

• What is a disk controller?

p. 364
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Magnetic Disks

• What is online storage?

• 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

• Others can be authorized to access your data

p. 365 Fig. 7-18
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Optical Discs
Push the button toslide out the tray.

• What are optical discs?

• Flat, round, portable metal discs made of metal,
  plastic, and lacquer

• Can be read only or read/write

Insert the disc,label side up.

• Most PCs include an optical disc drive

Push the same buttonto close the tray.
p. 366 Fig. 7-19
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Optical Discs

• How does a laser read data on an optical disc?

Step 2.If light strikesa pit, it scatters. If
light strikes a land, it is reflected back toward
diode.
Step 1.Laser diode shines a light beam
towarddisc.
p. 367 Fig. 7-20
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Optical Discs

• How is data stored on an optical disc?

• Typically stored in single track

• Track divided into evenly sized sectors that
  store items

single trackspirals to edgeof disc
disc sectors
p. 367 Fig. 7-21
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Optical Discs

• How should you care for an optical disc?

Do not exposethe disc to excessiveheat or
sunlight
Do store thedisc in a jewelbox whennot in use
Do noteat, smoke, ordrink neara disc
Do not stack discs
Do hold a discby its edges
Do not touchthe undersideof the disc
p. 368 Fig. 7-22
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Optical Discs

• What is a CD-ROM?

• Compact disc read-only memory

• Cannot erase or modify contents
• Typically holds 650 MB to 1 GB
• Commonly used to distribute multimedia and
  complex software

p. 369 Fig. 7-24
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Optical Discs

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

75X
Ranges from 48X to 75X or faster
75 ? 150 KBps 11,250 KBps or 12.25 MBps
75X is 150 KBps (KB per second)
48X 48 ? 150 KBps 7,200 KBps or 7.2 MBps
p. 369
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Optical Discs

• What is a Picture CD?

Step 3.At home, print images from Picture CD on
your ink-jet photo printer.
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.
At a store, print images to Picture CD at kiosk.
p. 370 Fig. 7-25
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Optical Discs

• What are CD-Rs and CD-RWs?

Must haveCD recorderor CD-R drive
CD-R (compact disc-recordable) cdisc you can
write on once
Cannot erasediscs contents
CD-RW (compact disc-rewritable) ceerasable disc
you can write onmultiple times
Must haveCD-RW softwareand CD-RW drive
p. 371
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Optical Discs

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

• High capacity disc capable of storing 4.7 GB to
  17 GB
• Must have DVD-ROM drive or DVD player to read
  DVD-ROM
• Stores databases, music, complex software, and
  movies

p. 372 Fig. 7-26
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Optical Discs

• How does a DVD-ROM store data?

• Two layers of pits are used, lower layer is
  semitransparent so laser can read through
• Some are double-sided
• Blu-Ray discs currently have a storage capacity
  of up to 27 GB

p. 372 Fig. 7-27
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Tape

• What is tape?

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

• Primarily used for backup

p. 374 Fig. 7-28
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Tape

• How is data stored on a tape?

• Sequential access

• Reads and writes data consecutively, like music
  tape

• Unlike direct access used on floppy disks, Zip
  disks, hard disks, CDs, and DVDs which can
  locate particular item immediately

p. 374
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PC Cards

• What is a PC Card?

• Adds capabilities to computer

• Credit-card-sized device commonlyused in
  notebook computers

p. 374 Figs. 7-297-30
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Miniature Mobile Storage Media

• What is miniature mobile storage media?

• Storage for small mobile devices

p. 375 Fig. 7-31
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Miniature Mobile Storage Media

• What are common types of flash memory cards?

p. 376 Fig. 7-32
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Miniature Mobile Storage Media

• How does one type of flash memory card work?

p. 377 Fig. 7-33
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Miniature Mobile Storage Media

• What is a USB Flash Drive?

• Plugs in a USB port on a computer or mobile
  device
• Storage capacities up to 4 GB
• May eventually make the floppy disk obsolete

p. 377 Fig. 7-34
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Miniature Mobile Storage Media

• What is a smart card?

• Stores data on microprocessor embedded in small
  card
• Input, process, output, and storage capabilities

p. 378 Fig. 7-35
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Microfilm and Microfiche

• What are microfilm and microfiche?

Store microscopic images of documents on roll or
sheet of film
Images recorded using computer output microfilm
recorder
p. 379 Fig. 7-36
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Microfilm and Microfiche

• How do life expectancies of various media compare?

• Microfilm and microfiche have longest life of any
  storage media

p. 379 Fig. 7-37
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Putting It All Together

• What are recommended storage devices for home
  users?

• 80 GB hard disk
• Online storage
• CD or DVD drive
• Card reader/writer
• USB flash drive and/or 3.5-inch floppy disk drive

p. 380 Fig. 7-38
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Putting It All Together

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

• 750 MB Zip drive
• 120 GB hard disk
• Online storage
• CD or DVD drive
• External hard drive for backup
• USB flash drive and/or 3.5-inch floppy disk drive

p. 380 Fig. 7-38
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Putting It All Together

• What are recommended storage devices for mobile
  users?

• 80 GB hard disk
• Online storage
• CD or DVD drive
• Card reader/writer
• Portable hard disk for backup
• USB flash drive, and/or 2 GB PC Card hard disk,
  and/or 3.5-inch floppy disk drive

p. 380 Fig. 7-38
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Putting It All Together

• What are recommended storage devices for power
  users?

• CD or DVD drive
• 300 GB hard disk
• Online storage
• Portable hard disk for backup
• USB flash drive and/or 3.5-inch floppy disk drive

p. 380 Fig. 7-38
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Putting It All Together

• What are recommended storage devices for large
  business users?

• Desktop computer
• 160 GB hard disk
• CD or DVD drive
• Smart card reader
• Tape drive
• USB flash drive and/or 3.5-inch floppy disk drive
• Server or Mainframe
• Network storage server
• 40 TB hard disk system
• CD-ROM or DVD-ROM server
• Microfilm or microfiche

p. 380 Fig. 7-38
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Summary of Storage
Floppy disks
Recordable DVDs
Zip disks
Rewritable DVDs
Internal hard disks
Tape
Portable hard disks
PC Cards
Recordable CDs
Flash memory cards and USB flash drives
Rewritable CDs
Smart cards, microfilm, and microfiche
DVD-ROMs
Chapter 7 Complete