Despite the fact that both CD and DVD disks have the same
news shape and size, the things they have in
common ends here. There are lots of
things between the two, such as for example what they hold
and how much they hold.
Information pits and lasers
a disk has microscopic grooves that will go
along in a spiral round the disc. CDs and
DVDs both have these grooves, with laser breams
applied to scan these very grooves.
Since you may understand, electronic information is represented
in people and zeroes. Inside of these discs, very
tiny reflective bumps known as lands and non
reflective holes known as pits, that can easily be
found near the grooves, reflect both the people
plus the zeroes of electronic information.
By reducing the revolution amount of the laser to 625mm
or maybe more infrared light, DVD technology has
was able to write in smaller pits in comparison
to the standard technology of CD. This will
enable a larger quantity of information per track
regarding the DVD. The minimal length allowed for a
pit in one single layer DVD-R is .4 micron, which
is obviously more than the .0834 micron that a
CD offers.
The tracks of a DVD are narrower too, which
permits more songs per disk, that also
translates into more capacity than a CD. The
avaerage single layer DVD holds 4.5 GB of data,
while a CD holds a simple 700 MB.
Layers
As stated above, a DVD has smaller pits and the
lasers need certainly to consider them. This is actually
achieved by utilizing a thinner plastic substrate
than in a CD, meaning that the laser requirements
to pass through a slimmer layer, with less
level to reach the pits. It is this decrease in
thickness that’s responsible for the discs
that have been only 0.6mm thickness – which is half
that of a CD.
Information access speed
DVDs will access data at an even faster rate than
a CD can. The common 32X CD-ROM drive reads
data at 4MB an extra, while a 1X DVD drive reads
at 1.38MB a second. This might be even faster than
an 8X CD drive.
Universal information format
The recording formats of CDs and DVDs are quite
different, as DVDs use UDF, or the Universal
Information Structure. This format allows data, video,
audio, and even a variety of all three to
be saved in a single file structure. The
advantage to this is any file can be accessed
by any drive, computer, or even consumer video clip.
CDs having said that are not compatible with
this structure.
