What is Optical Disk ?
OPTICAL DISK
Originally developed in the late 1960s , the
first optical disc , created by " James T.
Russell " , stored data as micron - wide
dots of light and dark . Russell's optical
storage system used a powerful backlight
to read the dots through a transparent
sheet of material on which the dots were
encoded. In later optical disc systems, a
laser read the dots and the data was
converted to an electrical signal. Then the
data was converted to audio or visual
TYPES OF OPTICAL DISK
- CD(Compact Disk)
- DVD(Digital Versatile Disc)
- BRD(Blu Ray Disk)
- HVD
■ CD (Compact Disk)
Compact Disk is a special type of disc, on
which data is usually written only once
and then it can be read any number of
times. Laser (Light Amplification by
Stimulated Emission of Radiation)
technology is used to write and read data
on them. Hence they are also called optical
discs. It is a disc made of plastic, on which there is an aluminum plate on both sides.
A thin layer is covered. The storage
capacity of a CD ranges from 680
megabytes to 800 megabytes, it is often
read at a speed of 1200 kilobits per second.
These are called CD-ROM drives. There are
also compact discs available these days
that can read and write data like a normal
floppy, but require a CD-writer. Being
relatively expensive Because of this, their
use is still limited. Compact discs are used
only, because all types of programs are
available on these days.
It can be mainly divided into three parts
1. CD ROM (Read Only Memory)
2. CD-R (recordable)
3. CD-RW (re-writable)
2. CD - R(Recordable):- It can be written
once, after that it is read only. Writing
data in CD - R is also addressed with burn
content. In the typical multisession burn
situation, data can be written to CD-R more
than once. In this, a special device CD
Writer is used to write data.
3.CD - RW :- CD - RW In addition to reading
data, there is also a facility to write many
times. CD - Writer is also used in this to
write data. Unlike floppy and hard disks,
CDs have a spiral-shaped track similar to a
clock spring, but not a track. These tracks
are divided into small sectors. CD rotates
at a varying speed. The ever-changing
speed of the disc is adjusted in such a way
that it passes through a constant Line
Velocity.
■ DVD(Digital Versatile Disc)
DVD stands for Digital Versatile Disc . A
DVD is a type of option media used for
storing digital data. It is the same size as a
CD , but has a larger storage capacity
Some DVDs are formatted specifically for
video playback , while others may contain
different types of data , such as software
programs and computer les. The original
DVD - Video format were developed in
1995. DVDs can be watched repeatedly
without reducing the quality of the video .
A standard video DVD can store 4.7 GB of
data which is enough to hold over 2 hours
of video . Some variations of DVD have
greater capacities . A dual - layer DVD ,
which has two layers of data on a single
side of the disc , can store & 8.5 GB of data .
A dual - sided DVD can store 9.4 GB of
data .
A dual - layer , dual - sided DVD can store
17.1GB of data . DVDs are also used to
distribute software programs. Since some
applications and other software (such as
clip art collections) are too large to fit on
a single 700 MB CD, DVDs provide a way to
distribute large programs on a single disc.
way to store a large number of files and
back up data.
There are four types of DVD
DVD RAM (Random Access Memory)
DVD ROM(Read Only Memory)
DVD R(Recordable)
DVD RW(Re-Writable)
□ DVD- RAM :- DVD-RAM (Random Access
Memory) can record and erase data
multiple times.
□ DVD -ROM :- Data in DVD-ROM (Read
Only Memory) can only be read, not
written.
□ DVD-R :- DVD-R (Recordable) can record
data only once and then act as a DVD-ROM.
□ DVD RW :- DVD-RW (Re-Writable) can
record and erase data multiple time.
■ BRD(BLU - RAY DISK)
Blu - ray is an optical disc format similar
to CD and DVD . It was developed for
recording and playing back high -
definition ( HD ) video and for storing
large amounts of data . A single Blu - ray
disc can hold up to 25 GB of data . Even a
double sided , dual layer DVD can only
hold 17 GB of data . Dual - layer Blu - ray
discs can store up to 50 GB of data . That
is equivalent to 4 hours of HDTV . Blu - ray
discs can hold more information than
other optical media because of the blue
lasers . The blue - violet laser has a
shorter wavelength than the red lasers
used for CDs and DVDs. This allow me
laser to focus on a smaller area , which
makes it possible to store more data on a
dise the same seas a CD or DVD.
■ HVD (Hosted Virtual Desktop)
A hosted virtual desktop ( HVD ) is a user
interface that connects to applications and
data that are stored on a cloud provider's
servers rather than on the user's computer
or the corporate network. An HVD is
sometimes referred to as a cloud - hosted
virtual desktop .
HVD is an optical disc technology
developed between April 2004 and mid -
2008 that can store up to several terabytes
of data on an optical disc 10 cm or 12 cm
in diameter .
The company responsible for HVD went
bankrupt in 2010 , and the product was
not launched.
Read More
What is ROM (Read Only Memory) ? & Types of ROM.
Output device and his types define and pictures.
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