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Table Of Contents  CertiGuide to A+ (Core Hardware)
 9  Chapter 0110:  Removable Media

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V  DVD

The Digital Versatile (Video) Disk, or DVD, is yet another example of the IT industry's ability to make one technology operate on an ever increasing scale.

A DVD drive is written, constructed and read in an almost identical fashion to that of a standard CD-ROM. The main difference is that the DVD drive uses a single frequency red laser to read and write data.

Because a laser light has a shorter wavelength than red light, data bits can be packed tighter on the same media.

This subtle change in technology allows a DVD to store an amazing 2.6GB of data per side. I say per side because DVDs are also capable of holding data on both sides of the disk.

DVD technology also employs a specific form of data compression that requires them to be read in a DVD drive only. CD-ROM drives are not capable of reading DVDs, but any DVD drive is capable of reading CD-ROM media.

[spacer]Blue Laser CD-ROMs / DVDs

For those of you who are intrigued, a DVD drive is capable of handling so much data simply because of a slightly smaller wavelength of laser light. If you remember back from your physics classes (I'm sorry to have to do this) you will remember that as you shorten the wavelength of light, you pass through the visible spectrum from red to yellow, to green, to blue. Going beyond that you get away from visible light in to ultraviolet radiation and so on.

Technology is being developed today that will use a blue light laser to read and write to CD ROM like disks. It is estimated that because of the vastly smaller wavelength of blue light compared to red light, a CD-ROM like disk may be able to hold 15GB of data, per side.



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