Digital versatile disk-recordable

Read Only media include the CD (Compact Disk), both Audio and CD-ROM (Read Only Memory) formats, and the more recently introduced DVD (Digital Versatile Disk) and DVD-ROM formats. DVD formats have a much higher data capacity than a CD-ROM, with the capacity depending on whether one or two recording layers are used. These read-only (i.e., prerecorded) media are largely the domain of entertainment and software distribution and publishing.196... 

Optical memory devices such as compact disks (CDs) and digital versatile disks (DVDs) are becoming essential items of audio and visual media as well as of external computer memory media. In these devices, a laser beamis used to record and read information. Because the laser spot can be focused to within a 1 fxm scale, optical memory can access higher density and capacity than conventional magnetic memories can. 

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