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what is  the difference between cd & dvd ?
 Question Submitted By :: Core-Java
I also faced this Question!!     Answer Posted By  
# 1
cd stores 700 MB of data.DVD stroes 3-4 Gb of data. now new
DVD can store 40 GB of DVD
Is This Answer Correct ?    121 Yes 38 No
# 2
cd means compaq disk where as dvd means digital volatile
cd has 700 MB of memory where as dvd has 4.7 GB of memory.
Is This Answer Correct ?    99 Yes 33 No
B Naresh Kumar
# 3
1) cd allows only half part of cinema.
2) cd thiner than dvd
3) cd less price then dvd.(lowest Rs-7)
4) cd means compaq disk.
5) cd has 700 MB of memory.

1) dvd allows four cinema.
2) dvd thiker than cd.
3) dvd high price.(Rs-17)
4) dvd means digital volatile disk.
5) dvd has 4.7 GB of memory.
Is This Answer Correct ?    102 Yes 38 No
# 4
A cd can be played by a dvd player but a dvd cant be played by a cd player.. 
Is This Answer Correct ?    74 Yes 14 No
# 5
The wavelength of the laser is reduced(from the 780mm
infrared light used in the CD) to 625mm cos of which DVD
technology has managed to write in smaller ‘pits’ as
compared to the standard CD. This allows for a greater
amount of data per track.The tracks of DVDs are narrower
which allows more tracks per disc this again translates into
more capacity than a CD.
Is This Answer Correct ?    59 Yes 8 No
# 6
Although both CD and DVD have the same media size and
shape, the similarity ends there. There are numerous points
of difference between the two, as listed below:

Data pits and lasers

A disc has microscopic grooves that move along in a spiral
around the disc. Both CDs and DVDs have these grooves.
Laser beams are applied to scan these grooves. As you may
be aware, digital information is represented in ones and
zeroes. In these discs, very tiny reflective bumps
(called ‘lands’) and non-reflective holes (called ‘pits’),
which are found alongside the grooves, reflect the ones and
zeros of digital information.

Here lies the difference – by reducing the wavelength of
the laser (from the 780mm infrared light used in the CD) to
625mm or more infrared light, DVD technology has managed to
write in smaller ‘pits’ as compared to the standard CD.
This allows for a greater amount of data per track. The
minimum length of a pit in a single layer DVD-RAM
[] is 0.4 micron, as
compared to 0.834 micron for a CD.

Also, the tracks of DVDs are narrower, allowing for more
tracks per disc, which again translates into more capacity
than a CD.


As explained above, DVDs have smaller ‘pits’ and the lasers
have to focus on them. This is done by using a thinner
plastic substrate than in a CD, which means that the laser
has to pass through a thinner layer, with less depth to
reach the pits. It was this reduction in thickness which
was responsible for discs that were only 0.6mm thick – half
that of a CD.

Data access speeds

DVDs access data at a much faster rate that do CDs. Here is
a comparison – a 32X CD-ROM drive reads data at 4M bytes
per second while a 1X DVD drive reads at 1.38M bytes per
second. That’s even faster than an 8x CD drive!

UDF (Universal Data Format)

Recording formats of CDs and DVDs are quite different. DVDs
use UDF (Universal Data Format []).
This allows data, video, audio or a combination of all
three, to be stored in a single file structure. The
advantage of this is that any file can be accessed by any
drive, computer or consumer video. CDs, however, are not
compatible with this format.
Is This Answer Correct ?    44 Yes 3 No
# 7
dvd is advanced device when compare to cd. 
Is This Answer Correct ?    64 Yes 27 No
# 8

Diameter 12cm 12cm
Thickness 1.2mm 1.2mm
Numerical Aperture 0.60 0.38 to 0.45
traise pitch 1.6mm 0.75Um
capasity 700mb 4.7gb
ratation speed 200-500 rpm 570-1600 rpm
modulation 8/14 8/16
user data rate 1.41mbps 11.08mbps
Is This Answer Correct ?    28 Yes 2 No
Arvind Kumar
# 9
On the basis of Storage capacity cd only stores 700 MB
whereas a dvd stores 3-4GB.And cost is different with both
of them.Now a days dvd increases its storage capacity.
Is This Answer Correct ?    27 Yes 5 No
Abnish Kumar Rajput
# 10
cd has only one layer but for dvd has two layers 
Is This Answer Correct ?    50 Yes 29 No

Other Core Java Interview Questions
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Integer.parse Int(bf.readLine(System.out.println("enter value for n["+m+"]:"))); can it run under this   1
what is the need to set path in java? how many ways to set path in java? Explain breif?   5
What do u mean by wrapper Class? What do u mean by Jvm... How do u change JVM for other OS? Or No need to Change ...? its like tricky EDS 6
What is an anonymous class? IBM 1
In how many ways we can the thread? in java   3
define System.out.println(); what is the meaning!   19
"We cannot create an object of interface but we can create a variable of it". Discuss the statement with the help of an example. (Plz help us to provide immediately.)   3
Are nested try statements are possible?   2
For more Core Java Interview Questions Click Here 

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