chapter 6 66 secondary storage. 6 © the mcgraw-hill companies, inc. 2002 objectives 1.floppy and...
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© The McGraw-Hill Companies, Inc. 2002
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Objectives
1. Floppy and hard disks
2. Cartridges and disk packs
3. Performance enhancements
4. Compact disks
5. Specialized disks
© The McGraw-Hill Companies, Inc. 2002
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Secondary Storage
• Save information
• Permanent storage
• Temporary storage
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Floppy Disks
• Removable
• Write-protect
• Parts– Tracks– Sectors
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New Standards
• Zip Disks– 250 MB
• SuperDisks– 120 MB
• HiFD disks– 200 MB
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Hard Disks
• Metallic disks
• Fast information
• Read-write heads
• Three types– internal hard disk
– hard-disk cartridge
– hard-disk pack
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Human hair
dust particle
fingerprint
smoke particle
disk head
disk surface
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Internal Hard Disk
• Inside system unit
• Advantage over
floppy disks
• Capacity: 80 gig
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Hard-disk Cartridges
• Easy removal
• Complements internal
– JAZ from Iomega
– SPARQ from SyQuest
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Hard-disk Packs
• Removable
• Massive storage capacity
• Common in mainframes
• Resembles stack of vinyl records
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Performance Enhancements
• Disk caching
• Redundant arrays of inexpensive
disks (RAID)
• File compression and decompression
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• Compact
• Permanent storage
• Laser beams reflect off pits
• Three types
Optical Disks
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CD-ROM
• Compact disc-read-only memory
• Not written to
• 650 MB capacity
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CD-R & CD-RW
• CD-Recordable or WORM
• CD-RW or rewritable optical discs
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CD-R for Music
• Download from Internet
• Arrange and play music
• Create custom CD-R or
CD-RW
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DVD
• Digital Versatile Disk or Digital
Video Disk
• Types– DVD-ROM– DVD-R – DVD-RAM or DVD-RW
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Magnetic Tape
• Fast, direct access
• Sequential access
• Storage and backup
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A Look to the Future
• Near-field recording devices
• Holographic storage systems