Although the CD and DVD media the same size and shape, the similarity ends there. A number of points difference between the two is as follows:
Data pits and lasers
microscopic grooves on a disc to move in a spiral around the disc. Both CDs and DVDs these grooves. A laser beam is used to scan these grooves. As you may know, information is represented in digital ones and zeros. In these discs, very tiny reflective bumps (called & # 145; lands & # 146;) and non-reflective holes (called & # 145; pits & # 146;), grooves located along which reflect the ones and zeroes of digital information.
There is a difference & # 150; reducing the wavelength of the laser (the 780mm infrared light used in CD) to 625mm or more infrared light, DVD technology has been a smaller letter & # 145; pits & # 146; than a standard CD. This allows a greater amount of data per track. The minimum pit length of a single-layer DVD-RAM [http://computer-information.info] 0.4 microns, compared to 0.834 microns with a CD.
In addition, the DVD tracks are narrower, allowing for more tracks on one disc, which is again reversed more capacity than a CD.
as explained above, DVDs, small & # 145; & # 146 pits; and lasers need to focus on them. This is done by a plastic substrate thinner than the CD, which means that the laser to pass through a thinner layer of less depth to reach the pits. This is the reduction in thickness, which was responsible for the plates, which are only 0.6 mm thick & # 150; half that of a CD.
The data access speed
DVD access data much faster to do CDs. Here is a comparison of & # 150; a 32X CD-ROM drive reads data of 4M bytes per second while a 1X DVD drive reads 1.38 bytes per second. That & # 146; and even faster than an 8x CD drive!
UDF (Universal Data Format)
Recording formats of CDs and DVDs is quite different. The DVD's UDF (Universal Data Format [http://pda-devices.info]). This allows the data, video, audio or a combination of all three, to be stored in a single file structure. This has the advantage that any file can be accessed for any drive, computer or consumer video. CDs, however, are not compatible with this format.