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Chapter 7 Storage. Chapter 7 Objectives. Discuss the various types of items that users store on computer media. Describe the characteristics of CDs and DVDs. Differentiate between storage devices and storage media. Differentiate among CD-ROMs, CD-RWs, DVD-ROMs, and DVD+RWs.

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chapter 7 objectives
Chapter 7 Objectives

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

Describe the characteristics ofCDs and DVDs

Differentiate between storage devicesand storage media

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

Describe the characteristics ofa floppy disk drive

Identify the uses of tape

Identify the uses of Zip disks

Discuss PC Cards and the various typesof miniature storage media

Describe the characteristics ofa hard disk

Identify uses of microfilm and microfiche

Identify the advantages of usingan Internet hard drive

memory versus storage
MEMORY VERSUS STORAGE
  • Memory
    • Fast
    • Short term
    • RAM is Volatile
    • Holds the current program and its data
memory versus storage4
MEMORY VERSUS STORAGE
  • Storage
    • Slower
    • Long term
    • Nonvolatile
    • Stores programs and data for future use
    • Can be thought of as both input and output device
      • Input: read data from storage into memory
      • Output: transfer data from memory to storage
memory versus storage5
MEMORY VERSUS STORAGE
  • Storage Capacity: how many bytes (characters) a storage medium can hold
    • Kilobyte (KB) = 1 thousand (1,000)
    • Megabyte (MB) = 1 million (1,000,000)
    • Gigabyte (GB) = 1 billion (1,000,000,000)
    • Terabyte (TB) = 1 trillion (1,000,000,000,000)
    • Petabyte (PB) = 1 quadrillion (1,000,000,000,000,000)
    • Exabyte (EB) = 1 quintillion (1,000,000,000,000,000,000)
storage

Stores …

Primary Storage

Memory (most RAM)

Items waiting to be interpretedand executed by the processor

Secondary Storage

Hard Disk

Operating system, applicationsoftware, user data and information

CDs and DVDs

Software, backups, movies, music

Miniature Storage Media

Digital pictures or small files tobe transported

Tape

Backups

Floppy Disk

Small files to be transported

STORAGE
  • What is access time?
    • Time it take storage device to locate and retrieve an item.

fastertransferrates

slowertransferrates

floppy disks
FLOPPY DISKS
  • Characteristics of a Floppy Disk
    • Magnetic
    • Size
      • 3.5-inch, 5.25-inch
    • Anatomy
  • Shutter
  • Shell
  • Liner
  • Disk
  • Hub
  • Write-protect notch
floppy disks8
FLOPPY DISKS
  • Characteristics of a Floppy Disk
    • Formatting: preparing a floppy disk for use
      • Track
      • Sector
      • Cluster
    • Capacity = sides x tracks x sectors per track x bytes per sector
    • File allocation table (FAT)

How the Floppy Drive Works

floppy disks9

Zip disk

FLOPPY DISKS
  • Zip Disks
    • 100 MB to 750 MB
    • The larger ones areequivalent to about500 diskettes!
    • Require a zip drive
hard disks
HARD DISKS
  • Primary media for storing software programs and files
  • Up to 160 GB capacity and more on PC hard disk
  • Consists of several platters
hard disks11

Sample Hard Disk Characteristics

Advertised capacity 40 GB

Platters 2

Read/write heads 4

Cylinders 16,383

Bytes per second 512

Sectors per track 63

Sectors per drive 78,165,360

Revolutions per minute 7,200

Transfer rate 100 MB per second

Access time 9 ms

HARD DISKS
  • Characteristics of a Hard Disk

actualdiskcapacity

hard disks12

Clearance is approximately two millionths of an inch

HARD DISKS
  • How a Hard Disk Works
    • Arms move read/write heads to proper location on the platters
    • Read/write head floats above platter
    • How it Works

hair

read/write head

dust

smoke

gap

platter

hard disks13

cylinder

track

HARD DISKS
  • How a Hard Disk Works
    • Cylinder: location of a single track through all platters
    • Disk cache improves performance
    • Partitions function as separate drives
hard disks14
HARD DISKS
  • External Hard Disks
    • Capacities up to 250 GB or more
  • Removable Hard Disks
    • Large storage capacity (60 GB or more)
    • Easily transported
    • Iomega’s Peerless disk (up to 40 GB)
  • USB Portable Drives
    • Capacity up to 1 GB
    • Fit on a key chain
hard disks15
HARD DISKS
  • RAID
    • Redundant array of independent disks
    • Increased reliability through redundancy
    • Expensive
    • Many levels of RAID
      • Mirroring
      • Striping
hard disks16

file 1 after defrag

disk after defragmentation process

HARD DISKS
  • Maintaining Data Stored on a Hard Disk
    • Preventative maintenance
      • Backup
      • Defragmentation
hard disks17
HARD DISKS
  • Internet Hard Drive (Online Storage)
    • Service on the web that provides storage to computer users
    • Fee usually involved
    • Iomega’s iStorage
cds and dvds

Disc sectors

Single track spirals to edge of disc

CDs and DVDs
  • Used to distribute software packages
  • Uses a laser beam to read and write data
  • Stores items in spiraling tracks
    • Sectors are all the same size
cds and dvds19
CDs and DVDs
  • CD-ROM
    • Compact disc read-only memory
    • Cannot be erased or modified
    • Can contain text, graphics, and video as well as sound
    • Capacity: about 650 MB = 450 diskettes to 1GB
    • CD-ROM drive speed

How the CD-ROM Works

cds and dvds20
CDs and DVDs
  • Writable CDs
    • CD-R (compact disc-recordable)
      • Multisession
      • Can read/write audio CDs and standard CD-ROMs
      • CD-ROM drives can usually read CD-R
    • CD-RW (compact disc-rewritable)
      • Erasable
      • Can read any format CD
      • Older CD-ROM drives can’t read them
    • Photo CD
cds and dvds21
CDs and DVDs
  • DVD-ROM (Digital versatile disc-ROM or Digital Video Disc-ROM)
  • Can hold much more data than CD-ROMs
    • 4.7 GB to 17 GB
  • Higher quality than CD-ROMs
  • Often used for video
cds and dvds22
CDs and DVDs
  • DVD variations
    • Digital movies and audio
    • DVD-R is single-session recordable
    • DVD+RW is rewritable
magnetic tapes
MAGNETIC TAPES
  • Cost effective way to store large amounts of infrequently used data
  • Types:
    • Reel-to-reel on older systems
    • Tape cartridge
  • Access technique:
    • Sequential access (tapes)
    • Direct access (floppy disks, hard disks, CDs, DVDs)
pc cards
PC CARDS
  • Thin, credit card-sized device that fits into a PC Card expansion slot of laptop
  • Add storage, memory, communications, and sound capabilities
other types of storage
OTHER TYPES OF STORAGE
  • Smart Cards
    • Similar in size to credit card or ATM card
    • Has an embedded microprocessor
    • Types:
      • Intelligent (with a microprocessor)
      • Memory card (storage only, as with a digital camera)
    • Prepaid smart cards
    • Electronic money
other types of storage26

Media Life Expectancies

Media Type Guaranteed Life Potential Life Expectancy Expectancy

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

OTHER TYPES OF STORAGE
  • Microfilm and Microfiche
    • Stores microscopic images of documents on roll or sheet film
    • Often used by libraries and banks due to length of life
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