Shelley - Discovering Computers - Chapter 6 - Storage

8/11/2019 Shelley - Discovering Computers - Chapter 6 - Storage

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Shelly Cashman Series

Discovering Computers

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

http://www.nextscan.com/wp-content/uploads/2013/05/FicheRoll-1110x406.jpg 21



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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