The differences between CD, and DVD discs can be confusing as far as terminology goes anyway. Both the CD as well as the DVD, has the same media size and shape. This is where their similarities end. There are many differences between the two disks such as what they will hold as well as how much they will hold. So how do you know the differences? They are quit simple.
A disc has microscopic grooves, which move along in a spiral around the disc. Both CD’s as well as DVD’s have these grooves. Laser beams scan these grooves. All digital information is represented with the use of ones and zeros. Inside these discs are very tiny reflective bumps. These bumps are known as “lands”. On the other hand, non-reflective bumps are known as “pits”. These non-reflective pits are found on the disc beside the grooves. These in return reflect both ones and zeros, of digital information.
DVDs have smaller pits than that of the CD. By reducing the wavelength of the laser to 625mm or more infrared light, these smaller pits are formed. With these smaller pits, discs are able to hold greater data per track than that of a CD.
Tracks on a DVD are narrower as well which in return allows for more tracks on the disc. This means there is more capacity on the DVD than the CD. The average DVD will hold 4.5 GB of data, while the CD will hold only 700MB.
Because the DVD has smaller pits the laser needs to focus on them. To achieve this, manufacturers use a thinner plastic substrate than the CD. This allows the laser to pass through a thin layer in order to reach the pits. This is the reason why DVD’s are thinner than CD’s
DVD’s are able to access data much faster than that of the CD’s. An example would be, the average 32xCD-ROM drive reads data at 4MB a second. The 1X DVD drive read at a rate of 1.38MB a second.
Another difference in DVD’s and CD’s is their formats. DVD’s use a UDF, (Universal Data Format). This type of format allows data, video, as well as audio to be stored in a single structure. This type of format can be accessed from not only a DVD player, but by any drive, computer, or consumer video. CD’s are not compatible with this type of format.