A Digital Versatile Disc is a superior form of disc when compared to CDs. It employs more advanced optical storage techniques, which can record data more densely onto the disc. Moreover, the DVD can be dual-layered and two sided, giving a maximum storage capacity of 17 gigabytes. That amount is more than some entire hard discs. However, the cost is also that much greater, which explains why CDs still dominate the market. DVDs are not far behind, though. Being 120 mm in diameter (4.7 inches) and 1.2 mm thick (0.05 inch), it is the same size as the CD. Like the CD, the DVD also stores the data on a spiral track and has pits and lands to store the data. However, these pits and lands are shallower and smaller, thus allowing for greater compression. The wavelength of the laser beam, which reads the DVD, is also shorter.
Once, DVDs were once said to be called Digital Video Disc, as it was first designed and used to hold video data only. As time passed, the number of DVD applications grew and the variety of data that can be stored on DVD is reflected in its present name, Digital Versatile Disc. Now, the DVD can hold audio, video and computer data, much like a CD.
