DVD has become a normal part of our digitized realities. DVD stands for “digital versatile discs” and are storage devices that use optical or laser technology to store video or data. A DVD is the same size as a CD and has the unique capability of holding large amounts of data. DVD starts getting more complicated when you specific functionality to them, so today we are here to set you straight!

DVD-ROM: ROM stands for “read-only memory”. It is capable of storing data that can be read later, but can only be written on once.

DVD-R: R stands for “readable” and can be written to one time, after which they become read-only devices.

DVD-RW: RW stands for “re-writable” and can both save and erase data repeatedly.

DVD-DL: Let commonly recognized, with the DL standing for “double layers”, can typically store up to 8GB. (Most DVDs are single-layered (DVD-SLs) and only hold around 4GB.)

How do DVDs store data?

DVD’s have microscopic grooves called “pits”. If you turn a DVD upside down you will notice the “pits” by their colored reflective surface. Lasers in DVD-burning drives burn the data into the pits at specific angles.

How does the data get read?

It is quite a fascinating process and much like our eyes. A DVD-ROM is equipped with two servomechanisms with a purpose to hold the DVD properly in place. One holds the lens and disc, while the second moves the drive head along the DVD. The laser’s light beam reflects off the pits on the disc into the lens. The reflection of data is translated by the device as needed.

Note: Hold a DVD with your fingers on the side of the disk. If the pits of the disc become dirty or scratched the data will be corrupted. Although there are machines that can fill in scratches on a disk it is only filling in the empty space, and you have still lost that small chunk of data. This type of fix is most noticeable when you are watching a movie on a repaired DVD.

Tim Grier
Computer Magician
CET Computer Magic
704-677-3035