Storage Devices

Storage

• Store information• Storage involve two processes:• Writing or recording the data so it can be

found later for use,• Reading the store data, then transferring it

into the computers memory.

Storage

• The physical materials on which data is stored are called storage media. E.g., diskette.

• The hardware components that write data to, and read data from, storage media are called storage devices. e.g., diskette drive.

Store Information

• A storage device is a hardware device designed to store information. There are two types of storage devices used in computers; a 'primary storage' device and a 'secondary storage' device.

Primary storage Secondary storage

Storage Devices

p. 354 Fig. 7-1 Next

Storage devices are used to data and programs permanently These devices are used to store large volume of data and program Also called backing storage devices ,secondary storage devices,

or auxiliary devices

Storage Medium(floppy disks,

hard disks, CDs)

Storage• How does volatility compare?

p. 356 Next

No

nvo

lati

le

Storage medium is nonvolatile—contents retained when power is off

Contents Contents retainedretained

Contents Contents available to useravailable to user

Memory(most RAM)

Screen Display

ON OFF

Vo

lati

le Display Display disappearsdisappears

Data andData andinstructions instructions

available to useravailable to user

Display Display appearsappears

Data and Data and instructions erasedinstructions erased

Memory is volatile—holds data and instructions temporarily

Types of Storage Media

Magnetic DiskOptical DiskSolid State Storage

Magnetic Disk It is most widely used storage media. A magnetic disk is a thin, circular metallic plate coated with

magnetic material. Information can be recorded on or read from the magnetic

surfaceFollowing are the types of Magnetic Disks:1. Floppy Disk2. Hard Disk

Magnetic Disks• What is a floppy disk?

Portable, inexpensive storage medium (also called diskette)

Thin, circular, flexible film enclosedin 3.5” wide plastic shell

shutter

shell

liner

magneticcoating

flexible thin film

metal hub

Magnetic Disks• What is a floppy disk drive?

Next

Floppy disk drive built intoa desktop computer

External floppy disk drive attaches toa computer with a cable

Also called secondary storage

One floppy drive, named drive A

Device that reads from andwrites to floppy disk

Magnetic Disks• What is a write-protect notch?

Next

Small opening with a cover that you slide Protects floppy disk from being erased accidentally

write-protected

not write-protected

notch closedmeans you

can write onthe disk

notch closedmeans you

can write onthe disk

notch openmeans you

cannot writeon the disk

notch openmeans you

cannot writeon the disk

Magnetic Disks• What is a hard disk?

Next

hard disk installedin system unit

High-capacity storage Consists of several

inflexible, circular plate that store items electronically

Components enclosed in airtight, sealed case for protection

Magnetic Disks

• Characteristics of Hard Disk:• Some important characteristics of Hard Disk are as follows: It provides large storage capacity The capacity of computer hard disk is from 2 to 80 GB and

more It is much faster than Floppy Disks It is used for storing data and programs It is more reliable than floppy disk Data stored on hard disk is safer than floppy disk

Push the same buttonto close the tray.

Optical Discs• What are optical discs?

Next

Most PCs include an optical disc drive

Flat, round, portable metal discs made of metal, plastic

Optical disk uses laser technology to read and write data

Can be read only or read/write

Optical disk storage

capacity is from 600 MB to over 1 GB with 14,500 tracks per inch (tpi).

It is much safer than magnetic media

Insert the disc,label side up.

Push the button toslide out the tray.

Optical Discs

• How should you care for an optical disc?

p. 368 Fig. 7-22 Next

Do store thedisc in a jewelbox whennot in use

Do hold a discby its edges

Do noteat, smoke, ordrink neara disc

Do not stack discs

Do not exposethe disc to excessiveheat or sunlight

Do not touchthe undersideof the disc

Optical Discs• Categories of Optical disks:1. CD2. DVD

• CD: Stands for Compact Disk It is most widely used media today A single CD can store from 650 MB to 1 GB The contents of CD can be read by CD driveDifferent types of CDs are as follows:1. CD-ROM2. CD-R3. CD-RW

Optical Discs• What is a CD-ROM?

Next

Compact disc read-only memory Cannot erase or modify contents Typically holds 650 MB to 1 GB Commonly used to distribute multimedia and complex software

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

Next

Must haveCD recorder

or 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 Discs•Digital Video Disk (DVD)It is similar to CD-ROMIt uses laser beamsIts storage capacity is much greater than CD-ROMIt can store up to 17 GB of data

Next

High capacity disc capable of storing 4.7 GB to 17 GB

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

Stores databases, music, complex software, and movies

Optical Discs

1. DVD-R– Stands for Digital Video Disk Recordable– It is similar to CD-R– The user write data on DVD-R only once but can read many

times– The data written on it cannot be erased

2.DVD-RW– it stands for Digital Video Disk rewritable– The user can write data on it many times by erasing the existing

contents