Wikijunior:How Things Work/DVD

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 compact discs but they store much more information in a different way.

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.

How does it get power?
A DVD player is powered by electricity. DVD players can either be powered by electricity or batteries.

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 cm if desired.

How DVDs are read
DVDs are read by a laser. The laser senses the pits and bumps and tells the DVD player what to play. The DVD player or computer often knows when the DVD is in or not. If the DVD is very scratched or is breaking or broken, it cannot be read by the laser.

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. The laser in the DVD player can also hurt your eyes.

What does it do?
It stores digital information that can be used by a DVD player or computer.

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.

How is it used?
DVDs can be used for:


 * Storing information, like pictures or video
 * Storing video games
 * Storing computer programs
 * And lots more!

How has it changed the world?
The DVD has modernized the current generations of video playing devices into the digital age.

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.