Chapter 7

Storage

Storage• What is storage?

Holds data, instructions, and information for future use Storage medium is physical material used for storage

Also called secondary storage What is a storage device?

It is the computer hardware that records and/or retrieves items to and from storage media.

What is reading? It is the process of transferring information from a storage medium into

memory.

Magnetic Disks• Magnetic Disks: they use magnetic particles to store items

such as data, instructions and information on a disk’s surface.

• Formatting: it is the process of dividing the disk into tracks and sectors so the operating system can store and locate data and information on the disk.

• Track: it is a narrow recording band that forms a full circle on the surface of the disk.

• Sectors: the disk storage locations consist of pie-shaped sections which break the tracks into small arcs. A sector stores 512 bytes of data.

• Clusters: for reading and writing purposes, sectors are grouped into clusters. It is the smallest unit of disk space that stores data and information. Also called allocation unit.

Magnetic Disks

•What are tracks and sectors?

Formatting prepares disk for use and marks bad sectors as unusable

Trackis narrow

recording bandthat forms fullcircle on disk

Sector stores up to512 bytes

of data

Magnetic Disks• What is a hard disk?

Also called the hard disk drive It is a storage device that contains

one or more inflexible circular platters that magnetically store data, instructions and information.

It is inside an airtight, sealed case inside the system unit.

Hard disks record in two patters:Longitudinal recordingPerpendicular recording

hard disk installedin system unit

Magnetic Disks• What is a head crash? Occurs when read/write head touches platter surface Spinning creates cushion of air that floats read/write head above platter Clearance between head and platter is approximately two-millionths of an inch A smoke particle, dust particle, or human hair could render drive unusable

clearance

read/write head

platter

hair

dustsmoke

Online Storage

• What is online storage?

– It is a service on the web that provides hard disk storage to computer users for a monthly fee.

– Files can be accessed from any computer with Web access

– Large files can be downloaded instantaneously– Others can be authorized to access your data

Floppy Disks Floppy disks are also called

a diskette. It is Portable, inexpensive

storage medium. Thin, circular, flexible film

enclosed in 3.5” wide plastic shell.

Floppy disk drive is a device that reads from and writes on a floppy disk. It is also called a secondary

storage. It is assigned to as DRIVE A:/

shutter

shell

liner

magneticcoating

flexible thin film

metal hub

Push the same buttonto close the tray.

Optical DiscsWhat are optical discs?

It is a type of storage media that consists of a Flat, round, portable metal discs made of metal, plastic, and lacquer

Can be read only or read/write

Most PCs include an optical disc drive

Insert the disc,label side up.

Push the button toslide out the tray.

Optical Discs• How is data stored on an optical disc?

Typically stored in single track

Track divided into evenly sized sectors that store items

single trackspirals to edgeof disc

disc sectors

Types of Optical Discs

• CD-ROM• CD-R• CD-RW• DVD-ROM• DVD-R• DVD+R• DVD-RW• DVD+RW• DVD+RAM

Optical Discs

• What is a CD-ROM?

Compact disc read-only memory

It is a type of optical disc that users can read but not write or erase.

Typically holds 650 MB to 1 GB Commonly used to distribute

multimedia and complex software

Optical Discs• What is a Picture CD?

Film developers offer

Picture CD service

Can be modified

using photo editing software

Stores digital versions of roll of film

Optical Discs• What are CD-Rs and CD-RWs? Must have

CD recorderor CD-R drive

Cannot erasedisc’s contents

CD-R (compact disc-recordable)—cdisc you can write on once

CD-RW (compact disc-rewritable)—ceerasable disc you can write on

multiple times

Must haveCD-RW softwareand CD-RW drive

Optical DiscsWhat is a DVD-ROM (digital versatile disc-ROM or digital video disc-ROM)?

Must have DVD-ROM drive or DVD player to read DVD-ROM

Stores databases, music, complex software, and movies

Blu-ray discs have storage capacity of up to 27 GB

HD-DVD discs have storage capacity of up to 45 GB

UMD can store up to 1.8 GB

PC Cards• What is a PC Card?

Adds capabilities to computer

Credit-card-sized device commonlyused in notebook computers

Miniature Mobile Storage Media

It allows mobile users easily to transport digital images, music, or documents to and from computers and other devices.

Storage for small mobile devices

Miniature Mobile Storage Media

• What is a USB Flash Drive?

Also called as a pen device Plugs in a USB port on a computer or

mobile device It is convenient for mobile users

because they are small and lightweight enough to be transported on a key chain or in a pocket.

Storage capacities up to 4 GB May eventually make the floppy disk

obsolete

Miniature Mobile Storage Media

• What is a smart card?

It is similar in size to a credit card.

Stores data on microprocessor embedded in small card

It contains: Processor Input, Process, Output, and Storage capabilities