welcome to cmpe003 personal computers: hardware and software
DESCRIPTION
Welcome to CMPE003 Personal Computers: Hardware and Software. Dr. Chane Fullmer Fall 2002 UC Santa Cruz. Class Information. Midterm results due back Friday HW #2 is back Avg score = 9.93 – Excellent !! . Assignments. Homework #3 – Due October 18 Design your own Web page - PowerPoint PPT PresentationTRANSCRIPT
Welcome to CMPE003 Personal Computers:
Hardware and Software
Dr. Chane FullmerDr. Chane Fullmer
Fall 2002Fall 2002
UC Santa CruzUC Santa Cruz
October 16, 20022
Class Information
Midterm results due back Friday HW #2 is back
– Avg score = 9.93 – Excellent !!
October 16, 20023
Assignments
Homework #3 – Due October 18– Design your own Web page– Keep in mind ---
The world at large will be able to see your page Don’t put private or sensitive information on your Web
page.
– Details and sample – see class page –http://www.soe.ucsc.edu/classes/cmpe003/Fall02/
If you need help uploading your files to your CATS account, take your disk to section..
Storage and Multimedia: The Facts and More
Chapter 6
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Objectives
List the benefits of secondary storage Identify and describe storage media available
for personal computers Differentiate among the principal types of
secondary storage Explain how data is organized, accessed, and
processed
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Secondary Storage Benefits
Semi-permanent Non-volatile Reliable Convenient – Locate and access data quickly
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Compressed storage– Diskette – about 500 printed pages – Optical disk – about 500 books
Economy– Savings in physical storage costs– Savings in the speed and convenience of filing
and retrieving data
Secondary Storage Benefits
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Types of Storage
Magnetic Disk Storage Optical Disks
– Magneto-optical– CD-ROM– CD-R– CD-RW– DVD-ROM
Magnetic Tape Storage
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Magnetic Disk Storage
Data represented as magnetic spots– Magnetized spot = 1– Absence of a magnetized spot = 0
Read– Converts the magnetized data to electrical impulses
Write– Converts electrical impulses to magnetized spots on
disk
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Disk Capacity
Size
MBolder hard disks
GBcurrent PC
TBcoming soon
What’s stored?
User documents
Software
Graphic images
Audio files
Video files
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Diskettes
Low capacity – small files Portable Flexible Mylar coated with
metallic substance Hard plastic jacket for protection 3 ½ inch, 1.44 MB
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High-Capacity Portable Disks
Larger files Portable High-capacity
– 120 / 200 MB– Can read and write standard diskettes– Ex: Superdisk
Zip disk (Iomega Corp)– 250 MB– not compatible with 3 ½ inch diskettes– Also Jaz disk (2GB)
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Data Compression
Why use?– Squeeze big files onto small disks– Speed up data transfer of files
Goal – Remove redundancy (minimize size)– Reduce to the minimal number of bits to store data
Techniques– Remove all extra space characters– Substitutes a smaller data string for a frequently occurring set
of characters– Software uses formula to determine how to compress
Different models used based on content (text, image, etc)– Must be decompressed to be used again
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Hard Disk
Various sizes Portability
– Generally non-portable– Removable hard disks available for PC
Rigid platter coated with metallic substance
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Disk Pack
Several platters
Airtight, sealed module
Mount disk pack on disk drive
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Disk Pack
Disk pack has set of access arms Two read / write heads per arm
– One reads top surface– One reads bottom surface
Access arms move together as a unit Only one read/write head works at a time
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Data DestroyedHead Crash
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Logical Layout of a DiskTrack
Concentric circles Passes under read/write head as disk rotates 1.44 MB diskette has 80 tracks on each surface
– Numbered 0 79 Each track stores the same amount of data
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Logical Layout of a DiskSector
Pie-shaped division of track
Holds a fixed number of bytes (512 bytes)
• Cluster– Adjacent sectors treated as a unit of storage– Fixed number (2-8 sectors)– Minimum space allocated to a file
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Same track on each platter
Store files across multiple platters
Reduces access time
Logical Layout of a DiskCylinder
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Logical Layout of a DiskZone Recording
• Assigns more sectors to tracks in outer zones
• More sectors = more data storage available
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Disk DriveRead / Write Operation
Disks rotate Access arm moves read/write
head Read / write operation begins
and continues until complete Data is transferred to/from
memory
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Access Time Components
Seek time– Travel time for moving heads over track
Head switching– Turning on correct head
Rotational delay– Waiting for sector to arrive under head (Avg ½ revolution)
Data transfer rate– Read/write bits on disk platter– Depends on density and rotational speed
October 16, 200224
Disk Caching
Required data read from disk into memory Adjacent data read into disk cache (special
area of memory) Program encounters a read instruction
– Checks disk cache If present, no physical read is required If not present, read from disk
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RAID
Redundant Array of Independent Disks
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Optical Disk
Greater capacity than other portable media Process
– Laser writes on metallic material spread over the surface of disk
– Heat from laser produces pits on disk surface– Reading – laser picks up light reflections from the
pits Technology
– ROM– WORM
October 16, 200227
MOMagneto-optical
Hybrid High-volume capacity Written multiple times Process
– Laser melts a microscopic spot– Magnet aligns crystals– Reading – laser picks up light reflection from
crystals
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CD-ROMCompact Disk Read-Only Memory
High capacity portable Read multiple times Cannot record Capacity – up to 680+ MB
– (450 standard 3 ½ inch diskettes)
Used for software distribution
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CD-RCompact Disc-Recordable
Cheap! – < 5 cents – or even free – Labels are the expensive part now
High capacity Portable Write once Read multiple times
– CD-R drive– CD-ROM drive
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CR-RWCompact Disk-Rewritable
High capacity Portable Read multiple times Record multiple times Some compatibility problems reading CD-
RW disks on CD-ROM drives
October 16, 200231
DVD-ROMDigital Versatile Disk
Originally named Digital Video Disk Larger capacity than CD-ROM
– Standard – Up to 4.7 GB 7 times more than CD-ROM
– Double layers – 8.5 GB– Double-sided – 17 GB
Data is packed more densely Read multiple times, Cannot record Can read CD-ROM disks
October 16, 200232
Benefits– Full-length movies– Audio quality comparable to audio compact disks– High-volume business data
Expected to replace CD-ROM in the near future
DVD-ROMDigital Versatile Disk
October 16, 200233
Hardware– CD-ROM or DVD-ROM– Sound card or sound chip– Speakers
MPEG (Motion Picture Experts Group)– Video standards that support full-motion video– Faster drive provides faster data transfer and
produces a smoother video
ApplicationsMultimedia
October 16, 200234
Magnetic Tape Storage
Plastic tape with magnetic coating Capacity based on density – bpi or cpi Magnetic tape unit
– Read/write head– Erase head erases previously recorded data
Inferior to disks– Not as reliable– Sequential access to data
Inexpensive Primarily for backup
October 16, 200235
Backup Systems
Prevent data loss– Fire– Natural disaster– Electromechanical failures of disk– User introduced errors– Software errors– Accidental data deletion
Store data in more than one place– Important data must be kept “offsite”
October 16, 200236
Bit Rot How long is my data good?
Not forever…… Bit rot occurs in all media
– Bit rot is a degradation of the medium itself over time Worst Best..
– Floppy 0 - 2 yrs– Tape 2 – 20 (with ECC)– Hard Disk 5 yrs– CD-RW 5 - 20 ?– CD-R 5 - 20 ?– DVD ???
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