Secondary storage devices.

Secondary storage devices
 Since Primary storage has a limited storage
and is not permanent ,We use secondary
storage devices.
 Secondary storage devices are used to store
large amount of data Permanently.

Types of Secondary storage devices
Types include:
 Hard disks.
 Floppy disks.
 CD ROMs.
 DVDs.
 Pen drives.
 Blue Ray Disks.

Floppy Disks-History
 The first floppy disks were 8 Inches in diameter.They hold
upto 256 KB.
 The next generation were 5.25 inches in diameter.It Could
hold up to 1.44 MB.It is a standard one.
 The next generation were 3.5 inches in diameter.
 These disks are held within a hard plastic case
 A spring loaded flap protects the disk from dust and
greasy fingers.
 Could hold up to 2.88 MB

Floppy Disks(Diskette)
 It is one of the oldest type of portable storage devices
still in use.
 It is used to transfer small files between computers.
 It is also used to store data as backup.
 Floppy disks are made of a flexible substances called
Mylar.
 A standard floppy disk can store 1.44Mb of data(300
A4 pages).

Floppy Disks(Diskette)
 The Floppy disks can take more space for
graphics/pictures than texts.
 All disks are formatted before data can be written to
disks.
Formatting:
 Formatting means Marking and dividing the disk into
tracks and sectors.
 Disks are divided into concentric circles called tracks.
 Each track is subdivided into sectors.

Floppy Disks (Diskette)
Parts of disks
 Read write head in the disks

Internal parts of floppy disk.
 Internal parts of a 3 1⁄2-inch floppy disk.
1) A hole that indicates a high-capacity
disk.
2) The hub that engages with the drive
motor.
3) A shutter that protects the surface when
removed from the drive.
4) The plastic housing.
5) A polyester sheet reducing friction
against the disk media as it rotates within
the housing.
6) The magnetic coated plastic disk.
7) A schematic representation of one
sector of data on the disk; the tracks and
sectors are not visible on actual disks.

Hard Disks
 A hard disk drive (HDD) is a data storage device used
for storing and retrieving digital information using rapidly
rotating discs (platter) coated with magnetic material.
 A HDD memories store information on one or more
circular platters which are continually spinning.
 Information is recorded on the surface of rotating data by
magnetic heads as tiny magnetic spots.
 These heads are mounted on arms.

Hard Disks
 Information is recorded in bands.
 Each band of information in a given disk is called a
track.
 The tracks are commonly subdivided into pie-shaped
sections called sectors.
 A motor rotates the disk at a rapid speed.
 Data are recorded on the tracks and read by using
read/write heads.

Compact Discs
 The Compact Disc or CDs are optical media.
 The CDs are relatively cheap and have a storage
capacity of up to 700Mb.
 The Compact Disc-Read Only Memory:
This is used only to store information ,not to
store data.
 Manufacturers use CD-ROMs to record information
including text ,graphics or audio on CD distribution.

CD-ROMs
 CD Roms use the same technology as audio Compact Discs.
 A master disc is created.
 Copies of the disc are created through a pressing
process
 The discs are aluminum sandwiched between plastic
 CDs are single sided.
Label
Acrylic
Aluminum
Plastic

CD-R(Recordable)
 Datas are recorded on these discs only once.
 The CD-Rs allow you to write on one part of the disc
on one time another part at a later time.
 Each part of CD-Rs allow you to write on only once and
can’t be erased.
Label
Acrylic
Aluminum
Plastic
Dye

CD-R(Recordable)
 CD Rs are made out of aluminum and plastic, but
also contain a dye layer
 This dye is modified by a laser when the disc is
being written.
 The laser heats up the dye and it becomes non-
reflective.

CD-RW(Rewritable)
 The CD-RW is an erasable disc.
 We can write it on multiple times like floppy or hard
disks.
 This is the main advantage in this.
 Too much of erasing fades the dye.
Label
Acrylic
Aluminum
Plastic
Dye

DVDs
 DVD is an optical storage device that looks like the
same as a CD.
 But,it ables to hold about 15 times as much
information and transfer it to the computer about 20
times as fast as CD-ROMs.
 Also called super density disk.
 It can hold 17 gigabytes of data.

DVD-ROM
 The DVD-ROM is high capacity optical disc capable of
storing 4.7 GB to 17GB.
 DVDs were originally developed for the movie
industry.
 It can read audio CDs,CD-ROMs,CD-Rs,CD-RWs

DVD-R
 It is similar to CD-Rs which allows user to write on
the disc once but read it many times.
 Dye layer is used for data writing.

DVD-RW
 Most writable DVD drives are DVD-RW.
 We can erase and read many times on them.
 DVD –R and DVD-RW have two additional formats
which are + and -.

Pen-Drive
 A pen drive, or a USB flash drive, is a portable data-
storage device.
 Pen drives have replaced the floppy drives of old and
have become the most popular data-storage devices
among consumers.
 Micro, lightweight and handy, a pen drive can be easily
carried from place to place by students, professionals,
academicians and independent tech consultants

Pen-Drive
 Currently available pen drives with storage capacities
ranging from 4GB and 32GB can be used to store
graphics-heavy documents, photos, music files and
video clips.

Design and implementation
1.USB standard male-A plug
2.USB mass storage control
device.
3.Test points.
4.Flash memory chip.
5.Crystal oscillator
6.LED(optional).
7.Write protect switch(option).
8.Space for second flash
memory.

Advantages Of Pen Drive
 Resistant to scratches, dust and magnetic fields.
 Consumes less power compared to other devices.
 Pen Drives are Universal
 Small Size for Easy Transport
 Affordability

Disadvantages of pen drives
 Due it’s small size, pen drives can be easily misplaced
or lost.
 Improperly wired USB ports can destroy the circuitry
of pen drives.
 Virus attack.

Blu-Ray Disc
 Blu-ray Disc (BD) is an Optical disc storage
medium designed to supersede the DVD format.
 The plastic disc is 120 mm in diameter and 1.2 mm
thick, the same size as DVDs and CDs.
 Developed by blu-ray disc association (which
includes Apple, Hitachi, HP, LG, Panasonic, Pioneer,
Philips, Samsung, Sharp, Sony).
 Wavelength of laser which reads data: 405 nm

Blu-Ray Disc-Name
 The blu-ray name is a combination of “blue”, for the
color of the laser that is used and “ray” for optical ray.
 The “e” in “blue” was purposefully left off, according to
the manufacturers, because an everyday word cannot
be a trademark.

Blu-Ray Disc -Formats
 It comes in four different formats:
BD-ROM (read only) : for reading recorded content.
BD-R (recordable) : for PC data storage.
BD-RW (rewritable) : for PC data storage.
BD-RE (rewritable) : for HDTV (high definition
television) recording.

Types Of Blu-Ray Disc
SINGLE LAYER :
- Can hold data up to 25/27 GB that means 2 hrs of HD
video or about 13 hrs of standard video.
DOUBLE LAYER :
- Can hold data up to 50 GB that means 4.5 hrs of HD video
or more than 20 hrs of standard video.

FEATURES of BD
With BD we can:
 Record HDTV without any quality loss
 Instantly skip to any spot on disc.
 Record one program while watching other on the
disc
 Create playlists
 Edit or reorder programs recorded on disc
 Automatically search for an empty space on the
disc to avoid recording over a program
 Access to web to download subtitles and other
extra features
 And many more…

Secondary storage devices.

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