DVD-ROM

The DVD (alternatively, Digital Video Disc or Digital Versatile Disc) is similar to a CD, but uses laser light with a shorter wavelength. This means that the size of the pits and lands will be considerably smaller, which in turns means that much more data can be stored on the same size disk. A DVD disk typically stores up to 4.7 GB of data, equivalent to about six CDs. This capacity can be doubled by using both sides of the disk. The high capacity of DVD-ROMs (and their recordable equivalent, DVD-RAMs) makes them useful for storing feature-length movies or videos, very large games and multimedia programs, or large illustrated encyclopedias.

The development of high-definition television (HDTV) standards spurred the introduction of higher capacity DVD formats. The competition between Sony’s Blu-Ray and HD-DVD (backed by Toshiba and Microsoft, among others) was resolved by 2008 in favor of the former. Blu-Ray offers high capacity (25GB for single layer discs, 50GB for dual layer).