1Copyright © Prentice Hall 2000 Storage and Multimedia Chapter 5 The Facts and More.

1Copyright © Prentice Hall 2000

Storage and Multimedia

Chapter 5Chapter 5

The Facts and MoreThe Facts and More


Secondary Storage

Secondary Storage allows for semi-Secondary Storage allows for semi-permanent storage of information.permanent storage of information.

Input Processing Output

SecondaryStorage


Benefits of Secondary Storage

By separating storage from the By separating storage from the computer, a number of benefits computer, a number of benefits can be derived:can be derived:

SecondaryStorage

• SpaceSpace• ReliabilityReliability• ConvenienceConvenience• EconomyEconomy


Space

• A diskette can hold the A diskette can hold the equivalent of 500 printed pages.equivalent of 500 printed pages.

• An optical disk can hold the An optical disk can hold the equivalent of 500 books.equivalent of 500 books.


Reliability

Data in secondary Data in secondary storage is basically storage is basically safe.safe.

Sometimes, however, Sometimes, however, disks do fail.disks do fail.


Convenience

Locating and Locating and accessing accessing electronic data is electronic data is much easier and much easier and faster than non-faster than non-electronic means electronic means of storing of storing information.information.

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Economy

Together, space-saving, Together, space-saving, reliability, and reliability, and convenience lead to convenience lead to cost savings for cost savings for businesses.businesses.

These savings are then passed on to These savings are then passed on to customers.customers.


Magnetic Storage of Data

Data is Data is represented as represented as magnetized magnetized spots spots on a disk.on a disk.

data


Bits on a Disk

A magnetized spot A magnetized spot represents a represents a 11 (bit). (bit).

The absence of a The absence of a magnetized spot magnetized spot represents a represents a 00 (bit). (bit).


Reading Data from Disk

Reading data on a Reading data on a magnetic disk means magnetic disk means converting the converting the magnetized data into magnetized data into electrical impulseselectrical impulses and sending them to and sending them to the processor.the processor.

Processing

SecondaryStorage


Writing Data to Disk

Writing data onto a Writing data onto a magnetic disk means magnetic disk means to convert electrical to convert electrical impulses from the impulses from the processor into processor into magnetic spots magnetic spots on on the disk.the disk.

Processing

SecondaryStorage


Types of Storage Media

There are various types of storage There are various types of storage media:media:

• DiskettesDiskettes• Hard disksHard disks• Optical disksOptical disks


Diskettes

Diskettes are made of a flexible mylar Diskettes are made of a flexible mylar disk enclosed in a hard casing.disk enclosed in a hard casing.

Advantages of diskettes:Advantages of diskettes:• portabilityportability• easy backup of fileseasy backup of files• new software releasesnew software releases


Anatomy of a Diskette

• Read/write opening

• Sector hole

• Disk

Shutter •

Casing •

Write-protect opening •


Zip Drives

Iomega’s Zip Drive holds 100 Iomega’s Zip Drive holds 100 Megabyte disks, seventy Megabyte disks, seventy times the capacity of times the capacity of traditional diskettes.traditional diskettes.


Hard Disks

A hard disk is a A hard disk is a metal platter metal platter coated with coated with magnetic oxide magnetic oxide that can be that can be magnetized to magnetized to represent data.represent data.


Benefits of Hard Disks

• SizeSize—more data can be stored on —more data can be stored on a hard disk than on a diskette.a hard disk than on a diskette.

• Necessary for graphicsNecessary for graphics—larger —larger storage capacity is required for storage capacity is required for audio, graphic, and video files.audio, graphic, and video files.

• Faster accessFaster access


Hard Disks in Groups

RAID (Redundant RAID (Redundant Array of Array of Inexpensive Disks) Inexpensive Disks) uses several small uses several small hard disks that hard disks that work together to work together to increase speed and increase speed and improve reliability.improve reliability.


Organizing Data on a Disk

There is more than one way to There is more than one way to organize data on a disk:organize data on a disk:

• Sector methodSector method• Cylinder methodCylinder method


Sector Method

In the sector method, each In the sector method, each tracktrack on a disk on a disk ……

is divided into is divided into sectors sectors that hold a that hold a specific number of specific number of characters.characters.


Cylinder Method

Using the cylinder Using the cylinder method to method to organize data on organize data on a hard disk, the a hard disk, the data is stored data is stored verticallyvertically within within the disk pack.the disk pack.


Optical Disks

An optical disk An optical disk consists of a disk consists of a disk with a metallic layer.with a metallic layer.

A laser is used to A laser is used to read/write to an read/write to an optical disk.optical disk.


Types of Optical Storage Media

The various types of optical storage The various types of optical storage media include:media include:

• Read-onlyRead-only• Write-once/read-manyWrite-once/read-many• Magneto-opticalMagneto-optical• CD-ROMCD-ROM• DVD-ROMDVD-ROM


Read-Only

These disks can These disks can only be read only be read from, not from, not written to.written to.

The information stored on dozens of The information stored on dozens of diskettes can be stored on one diskettes can be stored on one optical disk.optical disk.

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Write-once/Read-many

Often referred to as WORM, after Often referred to as WORM, after data is written on them, these data is written on them, these disks become a read-only medium.disks become a read-only medium.

WORM disks are ideal for securing WORM disks are ideal for securing original versions of valuable original versions of valuable documents and data.documents and data.


Magneto-optical

A magneto-optical disk combines A magneto-optical disk combines the the ability to write to diskability to write to disk [magnetic disk feature] with a [magnetic disk feature] with a high volume of storage high volume of storage capacity capacity [optical disk feature].[optical disk feature].


CD-ROM

CD-ROM stands for CD-ROM stands for compact disk, compact disk, read-only memoryread-only memory..

A CD-ROM is identical to audio A CD-ROM is identical to audio compact disks.compact disks.

Up to 660 MB of storage space is Up to 660 MB of storage space is available per disk.available per disk.


DVD-ROM

DVD stands for digital video disk.DVD stands for digital video disk.

A DVD-ROM can store from 4.7 GB A DVD-ROM can store from 4.7 GB (more than seven times that of a (more than seven times that of a CD-ROM) to 17 GB.CD-ROM) to 17 GB.

Such storage capacity is needed for Such storage capacity is needed for files containing both text, audio, files containing both text, audio, graphics, and video—in other graphics, and video—in other words, words, multimediamultimedia..


Multimedia

Multimedia is any combination of:Multimedia is any combination of:

• musicmusic• animationanimation• videovideo

• texttext• illustrationsillustrations• photosphotos• narrationnarration


Additional Multimedia Requirements

• CD-ROM drive, sound card, and CD-ROM drive, sound card, and speakersspeakers

• MPEG, if video will be usedMPEG, if video will be used• increased RAM capacityincreased RAM capacity• high-grade color monitorhigh-grade color monitor• vast amounts of secondary storage vast amounts of secondary storage

capacitycapacity


Popular Multimedia Titles

With which With which multimedia titles multimedia titles are you already are you already familiar?familiar?

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Magnetic Tape

Tape density refers to the stored number Tape density refers to the stored number of characters (or bytes) per inch.of characters (or bytes) per inch.

In businesses, magnetic tape is usually In businesses, magnetic tape is usually reserved for reserved for backupbackup purposes. purposes.


Organizing Stored Data

A lot of planning goes A lot of planning goes into determining into determining how user data will how user data will be received, be received, organized, stored, organized, stored, and later, and later, processed by the processed by the computer.computer.


Data: Getting Organized

To be processed by the computer, To be processed by the computer, data is organized into:data is organized into:– CharactersCharacters– FieldsFields– RecordsRecords– FilesFiles– DatabasesDatabases


File Organization

There are three major methods of There are three major methods of storing files in secondary storage:storing files in secondary storage:

• SequentialSequential• DirectDirect• IndexedIndexed


Sequential File Organization

In this method, if a particular record is In this method, if a particular record is wanted, all prior records must be read wanted, all prior records must be read before the desired one is reached. before the desired one is reached.

Tape storage is sequential file storage.Tape storage is sequential file storage.


Direct File Organization

In this method of In this method of organization, the organization, the computer does not computer does not have to read all have to read all preceding records.preceding records.

Disk storage is an Disk storage is an example of direct file example of direct file organization.organization.


Indexed File Organization

A compromise between sequential A compromise between sequential and direct file organization is the and direct file organization is the indexed method.indexed method.

In this example, records are stored In this example, records are stored in sequential manner; and the file in sequential manner; and the file also contains an also contains an indexindex—a —a directory which speeds up access directory which speeds up access to desired record.to desired record.


Accessing Stored Data

The time needed to The time needed to access stored data access stored data is determined by :is determined by :

• Seek timeSeek time• Head switchingHead switching• Rotational delayRotational delay


Seek Time

This is the time it This is the time it takes the access takes the access arm to get into arm to get into position over a position over a particular track.particular track.

access arm


Head Switching

Head switching is the Head switching is the activation of a activation of a particular read/write particular read/write head over a head over a particular track on a particular track on a particular surface.particular surface.


Rotational Delay

This is the delay This is the delay encountered from the encountered from the time when the access time when the access arms and read/write arms and read/write heads are in position heads are in position until the desired data until the desired data on the track moves on the track moves under it.under it.


Processing Stored Data

There are several There are several techniques for techniques for processing stored processing stored data:data:

• BatchBatch• TransactionalTransactional


Batch Processing

In this technique, transactions are In this technique, transactions are collected into batches and collected into batches and processed at a time when the processed at a time when the computer is more accessible.computer is more accessible.


Transaction Processing

In this method, transactions are In this method, transactions are handled immediately—fast enough handled immediately—fast enough for the result to come back and be for the result to come back and be acted upon right away.acted upon right away.


Conclusion

In the future, storage capabilities will In the future, storage capabilities will be even greater.be even greater.

This increased storage will benefit This increased storage will benefit law, medicine, science, education, law, medicine, science, education, transportation, businesses, the transportation, businesses, the government, and other groups that government, and other groups that rely on massive storage of data rely on massive storage of data and quick retrieval.and quick retrieval.

1Copyright © Prentice Hall 2000 Storage and Multimedia Chapter 5 The Facts and More.

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