Wikijunior:How Things Work/DVD
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DVD stands for "Digital Versatile Disc". A DVD is used to hold information that can be read by a computer using a laser. DVDs are used mainly for movies, television programs and computer programs like games. DVDs are the same shape and size as a compact discs but they store much more information in a different way.
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[edit] Who invented it?
The DVD was invented by a group of companies including most of the world's largest makers of home video equipment including Toshiba, Philips, Sony and Matsushita Electric.
[edit] How does it get power?
A DVD player is powered by electricity. DVD players can either be powered by mains electricity or batteries.
[edit] How does it work?
DVDs are of the same shape and thickness as CDs, and they are made using some of the same materials and manufacturing methods. Like a CD, the data on a DVD is held in the form of small pits and bumps on the disc. A DVD is made up of several layers of plastic that is 1.2 mm thick. Each layer is made by injection moulding plastic. This forms a disc that has tiny bumps (often called pits) arranged as a single very long spiral track of data. These bumps are where all the data is stored. The bumps and pits on a DVD are coded information.
Each writeable layer of a DVD has a spiral track of data. On single-layer DVDs, the track always circles from the inside of the disc to the outside. That the spiral track starts at the center means that a single-layer DVD can be smaller than 12 centimeters if desired.
[edit] How dangerous is it?
The DVD is not dangerous by itself unless it is broken. Then the pieces are very sharp and could cut your fingers - or your feet if you step on them.
[edit] What does it do?
It stores digital information that can be used by a DVD player or computer.
[edit] How does it vary?
The first DVDs had a single layer and could store around 4.5 Gigabytes of data. Later on scientists found a way to make more layers so it could store even more data. These multi-layered DVDs are called dual layer DVDs which can store around 8.5 Gigabytes of data. Nowadays there are two more types of DVDs which are called Blu-ray and HD-DVD that can store even more. The single layer Blu-ray disc can store 25 Gigabytes of data while the dual layer Blu-ray disc's can store 50 Gigabytes of data. The HD-DVDs can store around 15 Gigabytes of data per layer. The HD-DVDs are no longer available.
[edit] How has it changed the world?
The DVD has modernized the current generations of video playing devices into the digital age.
[edit] What idea(s) and/or inventions had to be developed before it could be created?
The DVD was seen as the next step from the video cassette. There are many inventions involved to make a DVD possible. First of all, the computer had to be invented. You'll realize this when you try to understand how DVD works. On a DVD disk there is coded in a binary form all the information one needs to record a picture.
