What is the difference between a DVD and CD?
A DVD is a disc containing video data, whereas a CD contains audio data. Both discs are read using a laser beam. The main difference between them is that DVDs contain both sound and video, whereas CDs only contain music. DVDs are usually larger than CDs because they contain more data. They also play back at higher speeds. In addition, DVDs are much more durable than CDs.
With all the new mediums for computer, music and entertainment, the ordinary consumer can quickly become confused by the terminology. CD drives as well as CD/RW drives and CD/DVD drives are all types of optical drives that can be found in desktop PCs. These optical drives tend to vary greatly depending on which computer system you are dealing with and what manufacturer it is. The most common and most basic forms of optical storage to be found in computers today are compact discs (CD) and digital versatile discs (DVD).
A CD drive houses a compact disc (or compact disk) which is defined as a “single layer, single track optical storage media that can be used for music or other data storage.” Computer discs that are used for computer usage generally have a capacity of 700 MB of data storage.
A CD/RW is a compact disc rewritable, which means it is a “rewritable optical disc format.” The CD/RW came into existence in 1997 and was first called the CD-Erasable (CD-E) until the name was changed to what it is today. A pre-recorded CD has the information on it permanently encoded on it it, however a CD/RW is made up of a phase-alloy recording layer that contains an alloy of silver, indium, antimony and tellurium (AgInSbTe). An infra-red laser beam is made use of to both heat and then melt the recording layer which becomes crystallized to the state it needs to be to be used for the proper function of recording material. The reflectance of the CD/RW gives it the appearance of a pre-recorded CD but they are different in their construction.
The CD/RW has never gained the popularity of CDs or DVDs or a combination therefore in the consumer market. It is important to note that the CD/RW recorder is capable of rewriting 700 MB of data to a CD/RW and it can be written to approximately 1000 times. CD/RW discs have to be completely blank before they are used again. The two methods of blanking a disc include “full” blanking and “fast” blanking. Full blanking is when the complete surface of the CD/RW disc is cleared or “blanked.” Fast blanking on the other hand is when only parts of the disc are cleared but it is generally enough to rewrite the disc. The parts that will be cleared are the meta data areas such as TOC PMA and pregap.
A DVD originally was meant only for videos and movies. Today DVDs are also readily used not just for movies but for computer as well. A DVD resembles a CD although DVDs have a much greater capacity for storing data than do CDs. DVDs are sometimes double sided but most are single sided. A single layer DVD disc can hold up to 4.7GB whereas a dual layer disc can hold up to 8.5 GB. DVDs are sometimes double sided but the great majority are single sided. A single layer double sided DVD can store up to 9.4 GB of information while a dual layer double sided DVD can store approximately 17 GB of information. A dual layer DVDS has only one surface layer that can be read from and written to and another second layer that is deeper and this one can also be read from and written, much like a CD/RW can be.
By far the CD/DVD drive is the most popular of all three types of drives. A CD drive enables you to do many things but it is often not enough, especially as computer users become more sophisticated and demand more and more from their computer systems. CD/RW drives also have their place but research studies are showing that the CD/DVD drive is coming out ahead of all other drives for consumers.
