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8/11/2019 Shelley - Discovering Computers - Chapter 6 - Storage
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Shelly Cashman Series
Discovering Computers
Storage
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8/11/2019 Shelley - Discovering Computers - Chapter 6 - Storage
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OBJECTIVES
Define storage
Identify the major storage devices
Explain how data is stored on floppy disksand hard disks
Explain how data compression worksExplain how data is stored on optical diskssuch as CD-ROMS
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CHAPTER 6 PRIMARYOBJECTIVES (cont.)
Explain how magnetic tape storage is usedwith computers
Describe other forms of storage: PC-Cards,RAID, and mass storage devices
Describe how special-purpose storagedevices, such as smart cards, are used
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WHAT IS STORAGE?
Stores programs and data
Writing/Recording data
Reading dataUsed as input and output devices
Variety of devices Storage Medium
Storage Device Capacity
Access Time
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Magnetic DisksWhat are tracks and sectors?
Track: a narrowrecording band thatforms a full circle onthe surface of thedisk
Pie shaped sectionsbreak the tracks intosmall arcs calledsectors
A sector can storeup to 512 bytes ofdata
A typical floppy diskstores data on bothsides of the disk
sector
18 per track
track
80 per
side
80 tracks per side X 18 sectors per track X 2 sides per disk X512 bytes per sector = 1,474,560 bytes
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MAGNETIC DISK STORAGE
Hard disks
Device is airtight to prevent contamination
Fixed disk Uses longitudinal recording or
Perpendicular recording
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MAGNETIC DISK STORAGE
Characteristics ofHard disks Capacity
Platters
Read/Write heads
cylinders
Sectors
tracks
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Hard Disks
What is a head crash?Occurs when a read/write head touches the surface of aplatter
The platters of the hard disk rotate at a high rate of speedwhile the computer is running
The spinning creates a cushion of air that floats theread/write head above the platter
hair
read/write head
dustsmoke
platter
gap
Clearance is
approximatelytwo millionths
of an inch
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Hard Disks
RAID – Redundant Array ofIndependent Disks
Miniature Hard Disks Pocket hard drive
External and Removable Hard Disks
External hard disk
Removable hard disk
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Hard Disk Controllers
Consists of a special-purpose chip and electroniccircuits that control the transfer of data,instructions, and information from a disk to and
from the system bus and other components in thecomputer. That is, it controls the interfacebetween the hard disk and the system bus. A diskcontroller for a hard disk, called the hard disk
controller, may be part of a hard disk or themotherboard, or it may be a separate adaptercard inside the system unit.
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Internet Hard Drives
Online Storage
Free or Fee based
Benefits
Data Accessibility
Share Data
Off site backup
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Floppy Disks
Also called diskette
Typical disk is 3.5 inches wide
Up to 1.44 MB
Floppy disk drive
Device that reads and writes on floppy disk
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Optical Discs
CD-ROM (compact disk read-onlymemory)
CD-R and CD-RW Burning
DVD-ROM
BD-ROM
HD DVD-ROM
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MAGNETIC TAPE
magnetically coated ribbon of plastic capable
of storing large amounts of data and
information at a low cost
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MAGNETIC TAPE
Reel-to-reel tape devices
Large computer systems
Two reels
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OTHER TYPES OF STORAGEDEVICES
PC cards
Very small
Most often used with portable computers Can store more than 300 MB of data
ExpressCard Modules
Smaller than PC card
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Miniature Mobile StorageMedia
allows mobile users easily to transportdigital images, music, or documents to
and from computers and other devicesFlash Memory Cards
CompactFlash (CF)
Secure Digital (SD) xD Picture Card
Memory Stick
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Miniature Mobile StorageMedia (cont.)
USB Flash Drive
sometimes called a pen drive or thumb
driveSmart Cards
stores data
on a thin microprocessor embedded in thecard
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Microfilm and Microfiche
Microfilm – roll of film
Microfiche – sheet of film
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Enterprise Storage Systems
A large business, commonly referred toas an enterprise, has hundreds or
thousands of employees in officesacross the country or around the world.Enterprises use computers andcomputer net- works to manage and
store huge volumes of data andinformation about customers, suppliers,and employees.
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Enterprise Storage Systems
Goal is to consolidate storage so operations runas efficiently as possible
Uses server rooms therefore,
CD-ROM Servers hold hundred/thousands of CD-ROMS, etc.
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Life Expectancies
Magnetic disks (tape) 3 – 5 years guaranteed
20 – 30 years possible
Optical discs (CD etc) 5 to 10 years guaranteed
50 to 100 years possible
Microfilm 100 years guaranteed
500 years possible
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Chapter 6 Complete
Powerpoint Adapted from from: http://www.powershow.com/view/3c5c2-MDFjM/Shelly_Cashman_Series_Discovering_Computers_powerpoint_ppt_presentation
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