Letter D

DECIBEL: A unit of a logarithmic scale of power or intensity called the power level or intensity level. The decibel is defined as one tenth of a bel where one bel represents a difference in level between two intensities I1, I0 where one is ten times greater than the other.

DVD (Digital Versatile Disc): DVD is a high density media, which looks like a CD-ROM. It can have one or two sides containing data, and each side can be single or double layer. Each layer has a 4.7giga bytes maximum capacity, so the total maximum capacity of a DVD is 18.8giga bytes. It uses the EFM storing scheme in order to increase reliability of data stored on it.