Storage Devices Powered by DeSiaMore1. Contents Storage Primary Secondary Access Method Floppy disk...

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Storage Devices

Powered by DeSiaMore 1

Contents

• Storage

• Primary

• Secondary

• Access Method

• Floppy disk

• Hard disk

• Optical disks

• Magnetic media

Overview

Information storage For future To share To modify

Permanent Storage secondary

storage, nonvolatile

Temporary storage RAM volatile

Secondary Storage

1. Secondary storage provides permanent or non-volatile storage:

2. This is accomplished by writing files to and reading from the secondary storage device.

• Writing- Is the process of serving information to the secondary storage device.

• Reading- Is the process of accessing information from secondary storage.

Characteristics of Secondary Storage devices

• Media or medium which is the actual physical material that holds the data and programs

• Capacity measures how much a particular storage medium can hold

• Storage device are hardware that reads data and programs from storage media. Most also write to storage medium

• Access speed or access time measures the amount of time required by the storage devices to retrieve data and program.

Storage devices can be categorized as magnetic or optical

Magnetic storage are such as diskettes, hard disk, high capacity floppy disks, and magnetic tapes

Optical storage are compact disks CD-ROM, DVD-ROM, CD-R, CD-RW etc

Categories of Storage Devices

Floppy Disks

• Floppy disks are often called diskettes or simply disks.

• They are portable and removable storage media

• They use flat circular pieces of Mylar plastic that have been coated with magnetic material.

Traditional Floppy Disk

Traditional floppy disks:

1.44MB

3.5 inch

2HD-two side high density

How a Disk Drive Works

Metal shutter

Hard plastic jacket

Write protection notch in the open position

Hard Disks

Metallic disks Composed of metallic rather than plastic disks Fast information storage and retrieval (write and

read) Read-write heads

Materials that can cause a Materials that can cause a head crashhead crash

Internal Hard Disk Inside system unit for storing the

operating system, other programs and large data files.

Motor with access arm and read-write heads.

Many advantages over floppy disks. Capacity (up to thousands

times a single floppy) Speed (twenty times the

speed)

Hard-Disk Packs

Removable, massive storage capacity

Common in mainframes Resembles stack of record albums

Optical disks use laser technology. CD and DVD are optical disk formats.

Compact, high capacity form of permanent storage

Laser beam writes by creating a pattern of pits (holes) and lands (flat areas) to encode data bits

Laser beams reflect off the pits and lands to read the data

Optical Disks

CD-ROM

Compact disc-read-only memory

Not written to

650 MB capacity

CD-R & CD-RW

CD-Recordable or WORM

(write once, read many)

CD-RW or rewritable optical discs

Digital Versatile Disk or Digital Video Disk

Up to 4.7 gigabytes a capacity, seven times CD DVD-ROM- provide high quality, movie length videos

DVD-R- consumer recordable version

DVD-RAM or DVD-RW- rewritable version of 2.6 to 5.2 GB storage capacity

Magnetic Tape

Disks offer fast, direct access to data programs Tapes offer sequential access (fast forwarded or rewound)

Storage and backup Forms of tape storage are:

Magnetic tape streamers Magnetic tape reels

Backup tape cartridge units used with

microcomputer systems

Capacities range from 120 MB to 5 GB

Magnetic Tape Streamers

Magnetic Tape Reels

Used with minicomputer and mainframe

computers

Often 1/2 inch wide and 1/2 mile long

Stores 1600 to 6400 characters per inch

Tapes are run on magnetic tape drives or

magnetic tape units

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