The document discusses different types of storage devices and media, describing the characteristics of magnetic disks like hard disks, optical discs like CDs and DVDs, as well as other storage technologies. It covers the basics of how these storage devices work, their capacities and speeds, and differentiates between read-only, recordable, and rewritable variants. The goal is to help students understand computer hardware storage and how various storage devices and media store and retrieve data.

1. Discovering Computers 2008
Chapter 5
Storage

2. 2
Chapter 5 Objectives
Differentiate among CD-ROMs,
Differentiate between storage devices recordable CDs, rewritable CDs,
and storage media DVD-ROMs, BD-ROMs, HD DVD-
ROMs, recordable DVDs, and
Describe the characteristics of rewritable DVDs
magnetic disks
Describe the characteristics of Identify the uses of tape
a hard disk
Discuss various types of miniature, Discuss PC Cards, ExpressCard
external, and removable hard disks modules, and the various types of
miniature storage media
Describe the characteristics
of optical discs Identify uses of microfilm and
microfiche

3. 3
Learning Outcome
Successful students will be able to:
Describe the characteristics of computer hardware
devices and explain their functionalities.

4. 4
Storage
What is storage?
Holds data, instructions, and information for future use
Storage medium is physical material used for storage
Also called secondary storage

5. 5
Storage
What is capacity?
Number of bytes (characters) a storage medium can hold
Kilobyte (KB) 1 thousand
Megabyte (MB) 1 million
Gigabyte (GB) 1 billion
Terabyte (TB) 1 trillion
Petabyte (PB) 1 quadrillion
Exabyte (EB) 1 quintillion
Zettabyte (ZB) 1 sextillion
Yottabyte (YB) 1 septillion

6. 6
Storage
How does volatility compare?
Storage medium is nonvolatile—contents retained when
power is off
Memory is volatile—holds data and instructions temporarily
ON OFF
Screen Display Display Display
Volatile
appears disappears
Memory Data and Data and
(most RAM) instructions instructions erased
(chips on motherboard) available to user
Nonvolatile
Storage Medium Contents Contents
(floppy disks, Zip disks, available to user retained
hard disks, CDs)

7. 7
Storage
What is a storage device?
Hardware that
Reading records and Writing
Process of transferring
retrieves items Process of transferring
items from storage to and from items from memory
media to memory storage media to storage media
Functions as source Creates output
of input

8. 8
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
faster Transfer rates Stores …
transfer
rates Primary Storage
Memory (most RAM) Items waiting to be interpreted
and executed by the processor
Secondary Storage
Hard Disk Operating system, application
software, user data and information
Flash Memory Cards Digital pictures or files
and USB Flash Drives to be transported
CDs and DVDs Software, backups, movies, music
Tape Backups
slower
transfer Floppy Disk Small files to be transported
rates

9. 9
Access time & Transfer rate
Memory accesses items in billionths of a second
(nanoseconds)
Storage devices access items in:
thousandths of a second (milliseconds) or
millionths of a second (microseconds)
Transfer rate is the speed with which data, instruction &
info transfer to & from a device, stated as:
KBps & MBps

10. 10
Magnetic Disks
Use magnetic particles to store items on a disk’s
surface
Alignment of magnetic particles represents the data
– either a 0 bit or a 1 bit
Must be formatted first:
Dividing the disk into tracks & sectors, so the OS can
store & locate items on disk
A sector stores up to 512 bytes of data

11. 11
Magnetic Disks
Track
Sector
is narrow
recording band stores up to
that forms full 512 bytes
circle on disk of data
Formatting prepares disk for use

12. 12
Magnetic Disks
For reading & writing purpose, sectors (2-8,
depending on OS) are grouped into clusters
Cluster (allocation unit) is the smallest unit of disk
space that stores an item
Each cluster holds data from only one file
Even if a file consists of only few bytes, it uses an
entire cluster
One file, anyhow, can span many clusters
Sometimes, a sector has defect & cannot store data.
When format, OS marks these bad sectors as
unusable

13. 13
Magnetic Disks
hard disk mounted
in system unit
What is a hard disk/hard disk drive/hard drive?
High-capacity storage: 80 – 750GB & more
Consists of several inflexible,
circular platters that store items
electronically
Components enclosed in airtight,
sealed case for protection
Longitudinal recording
Perpendicular recording
Fixed h/d & portable h/d

14. 14
Magnetic Disks
What are characteristics of a hard disk?
Sample Hard Disk Characteristics
Advertised capacity 500 GB
Platters 4
Read/write heads 8
Cylinders 16,383
Bytes per second 512
Sectors per track 63
Sectors per drive 973,773,168 actual
disk
Revolutions per minute 7,200 capacity
Transfer rate 300 MB per second
Access time 8.5 ms

15. 15
Magnetic Disks
h/d capacity determined from num of platters and
composition of magnetic coating on the platters
Platter
diameter: 3.5 inches in– desktop; 2.5 inches – notebook &
mobile devices
made of aluminum, glass or ceramic – coated with alloy –
allow items to be recorded magnetically on its surface. The
coating is 3 millionths of an inch thick
Each has 2 read/write heads, one for each side
h/d arms move read/write heads to the proper location –
read & write items in the drive as it barely touches the
disk/s recording surface
Location of read/write heads referred to by its cylinder – a
vertical section of a track that passes through all platters

16. 16
Magnetic Disks
How does a hard disk work?
Step 3.
When software requests a
disk access, read/write
heads determine current
Step 2. or new location of data.
Small motor spins
platters while
computer is running.
Step 4.
Head actuator positions
read/write head arms over
Step 1. correct location on platters
Circuit board controls to read or write data.
movement of head actuator
and a small motor.
platters rotate at high speed: 5400 – 15000 revolutions per minute (rpm) – until power
is removed

17. 17
Magnetic Disks
platter
What is a cylinder? track
Vertical section of sector
track through all
platters
Single movement
of read/write head
arms accesses all
platters
read/write
in cylinder head
platter
sides
cylinder

18. 18
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

19. 19
Magnetic Disks
What is a disk cache/buffer?
Portion of memory
(memory chip on h/d) that
processor uses to store
frequently accessed items
2MB – 16MB
(the greater, the faster the
h/d)
first request second request
for data—to disk cache for data—to hard disk

20. 20
Magnetic Disks
What is RAID?
Redundant Array of Independent Disks
Connects multiple smaller disks into a single unit that
acts as a single large hard disk
What is backup?
A duplicate of a file, program or disk placed on a
separate storage medium that user can use in case the
original is lost, damaged or destroyed
What is density?
Number of bits in an area on a storage medium
High density = high capacity

21. 21
method-
Backup method- Hard Disks
How does RAID work?
Disk system that duplicates data, instructions, and information to improve
data reliability
Mirroring has one backup disk for each disk
Striping stores data across multiple disks
mirroring
(RAID Level 1)
striping

22. 22
Magnetic Disks
What is a miniature hard disk?
Provide greater storage capacities than flash memory:
4GB – 160GB – mostly use perpendicular recording
Smaller than notebook computer hard disks
A pocket hard drive is a self-contained unit
User can insert in & remove from a slot in a device or
a computer or plug-in a USB port on a computer

23. 23
Magnetic Disks
What are external hard disks and removable hard disks?
Used to back up or transfer files
External hard disk—freestanding Removable hard disk—hard disk
hard disk that connects to system unit that you insert and remove
from hard disk drive

24. 24
External & Removable Hard Disk
External h/d:
Connects with cable to USB or FireWire port on SU
Some include multiple h/d act as one, having capacity up to 1TB
Removable h/d:
Sometimes the drive is built in the SU
Others are external devices – connect with cable to USB or
FireWire port on SU.
Has up to 500GB capacity
ADVANTAGES??

25. 25
Magnetic Disks
What is a disk controller?
Chip and circuits SATA (Serial Advanced
Serial
that control transfer Technology Attachment) controller
Attachment)
uses serial signals to transfer data,
of items from disk instructions, and information
EIDE (Enhanced Integrated Drive SCSI controller supports up to fifteen
E
Electronics) controller supports four devices including hard disks, CD
hard disks, provides connections for and DVD drives, tape drives, printers,
CD and DVD drives scanners, network cards

26. 26
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
REASONS??

27. 27
Magnetic Disks
What is a floppy disk?
Portable, inexpensive storage medium
(also called diskette)
Consists of thin, circular, flexible plastic
Mylar film with magnetic coating
Enclosed in 3.5” wide plastic shell
Storage capacity: 1.44MB
Access time: 84 ms
Transfer rate: 250 – 500KBps
Contains 80 track on each side
≈ 18 sectors per track

28. 28
Magnetic Disks
liner
shutter
metal
hub
magnetic flexible
shell coating thin film

29. 29
Magnetic Disks
sector
18 per track
track
80 per
side
80 tracks per side X 18 sectors per track X 2 sides per disk X 512
bytes per sector = 1,474,560 bytes

30. 30
Optical Discs
Push the button to
What are optical discs? slide out the tray.
Flat, round, portable
metal discs made of
metal, plastic, and
lacquer
Can be read only or Insert the disc,
read/write label side up.
Most PCs include an
optical disc drive
Push the same button
to close the tray.

31. 31
Optical Discs
How does a laser read data on an optical disc?
disc label
lens pit land lens
Step 3.
Step 2. Reflected light is
0 1
If light strikes deflected to a
a pit, it scatters. light-sensing diode,
If light strikes a which sends digital
prism land, it is prism signals of 1 to
light- reflected back light- computer. Absence
Step 1.
sensing toward diode. sensing of reflected light is
Laser diode
diode diode read as digital
shines a light
laser laser signal of 0.
beam toward
disc. diode diode

32. 32
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 track
spirals to edge
of disc
disc sectors

33. 33
Optical Discs
How should you care for an optical disc?

34. 34
Optical Discs
What is a CD-ROM?
Compact disc read-only memory
Single-session disc
Cannot erase or modify contents
Typically holds 650 MB to 1 GB
Commonly used to distribute multimedia and complex software

35. 35
Optical Discs
What is the data transfer rate of a CD-ROM drive?
Ranges from
48X to 75X 75X
or faster
75 × 150 KBps = 11,250 KBps
X is 150 KBps
or 11.25 MBps
(KB per second)
48X:
48 × 150 KBps = 7,200 KBps
or 7.2 MBps

36. 36
Optical Discs
What is a Picture CD?
Film developers Can be
Stores digital
offer modified
versions of
Picture CD using photo
roll of film
service editing software
Step 1.
Drop off film to Step 3.
be developed.
At home, print images
Mark the Picture
from Picture CD on
CD box on the Step 2. your ink-jet photo printer.
film-processing When you pick up
envelope. prints and negatives, a At a store, print images to
Picture CD contains Picture CD at kiosk.
digital images of each
photograph.

37. 37
Optical Discs
What are CD-Rs and CD-RWs? Must have
CD recorder
or CD-R drive
CD-R (compact disc-recordable)
— multisession optical disc
— can write on once, but not erase Cannot erase
disc’s contents
CD-RW (compact disc-rewritable)
— erasable multisession disc
ce
— can write on multiple times
Must have
CD-RW software
and CD-RW drive
Disc reliability drop with each successive
rewrite
Speed: 52/24/52 [write – 52X or more, rewrite –
24X or more, read – 52X or more ]

38. 38
CD-
CD-R and CD-RW drives
CD-
writes
CD-R drive
(speed: 40/48)
writes
CD-RW drive
(speed: 52/24/52)
+ CD-RW software

39. 39
CD-
CD-R and CD-RW drives
CD-
reads
CD-R drive
(speed: 40/48)
reads
CD-RW drive
(speed: 52/24/52)

40. 40
Video CD
Store video on a CD-R
Can be played in CD or
DVD drives, DVD players &
some game consoles
Hold 74 – 80 minutes of
video
Digital media
copy
RIPPING
PROCESS

41. 41
Optical Discs
What is a DVD-ROM (digital versatile
disc-ROM or digital video disc-ROM)?
Must have DVD-ROM drive or
DVD player to read DVD-ROM
Stores databases, music,
complex software, and movies
Blu-ray discs have storage
capacity of up to 100 GB
HD-DVD discs have storage
capacity of up to 60 GB
UMD can store up to 1.8 GB

42. 42
Optical Discs
How does a DVD-ROM store data?
1. Dense disc – closer pits
2. Two layers of pits are used, lower layer is
semitransparent so laser can read through
3. Some are double-sided
Many types of recordable and rewritable DVDs are available
DVD-R and DVD+R
DVD-RW and DVD+RW

43. 43
Tape
What is tape?
Magnetically coated plastic ribbon
capable of storing large amounts
of data at low cost
Primarily used for backup
Low cost
Long term storage

44. 44
Tape
How is data stored on a tape?
Sequential access
Reads and writes data consecutively, like
music tape
Unlike Direct access/Random access— used
on hard disks, CDs, and DVDs — which can
locate particular item immediately

45. 45
PC Cards and ExpressCard Modules
What are PC Cards and ExpressCard Modules?
Adds capabilities to computer
Credit-card-sized device commonly used in
notebook computers
Add memory, storage, communications,
multimedia, and security capabilities to a computer

46. 46
Miniature Mobile Storage Media
What is miniature mobile storage media?
Storage for small mobile devices

47. 47
Miniature Mobile Storage Media
What are common types of flash memory cards?
CompactFlash Secure Digital xD Picture Card
Memory Stick Memory Stick PRO Duo

48. 48
Miniature Mobile Storage Media
How does one type of flash memory card work?

49. 49
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 64 GB
May eventually make the
floppy disk obsolete
Also called U3 Smart device
Transfer rate: 12 MBps

50. 50
Miniature Mobile Storage Media
What is a smart card?
Stores data on microprocessor embedded in small card
Input, process, output, and storage capabilities
Used to store medical records, vaccination data, and other
health-case and identification information; tracking information
– employee attendance or customer purchase, authenticating
users for building access
Are credit cards
smart cards?

51. 51
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
Microfilm — 100- to Microfiche — small sheet
215-foot roll of film of film, usually 4” × 6”
Used to store back issues of newspapers, magazines, inactive
files, transactions and cancelled checks,…

52. 52
Microfilm and Microfiche
How do life expectancies of various media compare?
Microfilm and microfiche are inexpensive % have longest life of
any storage media

53. 53
Putting It All Together
What are recommended storage devices for home
users?
250 GB hard disk
Online storage
CD or DVD drive
Card reader/writer
USB flash drive

54. 54
Putting It All Together
What are recommended storage devices for small
office/home office (SOHO) users?
500 GB hard disk
Online storage
CD or DVD drive
External hard drive for backup
USB flash drive

55. 55
Putting It All Together
What are recommended storage devices for mobile
users?
100 GB hard disk
Online storage
CD or DVD drive
Card reader/writer
Portable hard disk for backup
USB flash drive

56. 56
Putting It All Together
What are recommended storage devices for power
users?
1.5 TB hard disk
Online storage
CD or DVD drive
Portable hard disk for backup
USB flash drive

57. 57
Putting It All Together
What are recommended storage devices for large
business users?
Desktop computer
500 GB hard disk
CD or DVD drive
Smart card reader
Tape drive
USB flash drive
Server or Mainframe
Network storage server
40 TB hard disk system
CD-ROM or DVD-ROM server
Microfilm or microfiche

58. 58
Summary of Storage
Internal hard disks
HD DVD discs
External and removable hard disks
Recordable and Rewritable DVDs
Floppy disks
Tape
CD-ROMs
PC Cards and ExpressCard
Recordable and Rewritable CDs modules
Flash memory cards and
USB flash drives
DVD-ROMs
Smart cards, microfilm, and
microfiche
Blu-ray Discs (BDs)
Chapter 5 Complete