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

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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

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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

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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

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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

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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

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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”

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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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