The compact disk (or cd) is a donut shaped disc and acts like a memory. But once files are placed into a compact disk, they cannot be removed, copied or edited unless if special programs (such as cd burners) are used. This makes them different to a usb device. PSP's also use cd's, however, their cd's are different to a normal cd, and are known as a umd.

The computer reads a cd by shining a laser over the silver side (That is the side opposite to the one which has writing/pictures). Information is placed inside this side of the cd and the computer picks it up with its laser and displays in the moniter. This also explains the reason the cd spins around while it is in the cd rom, because the laser only shines on a certain part of the disc so the disc must be spun in order to collect the information from the other side. Not to mention, if the silver side of the cd has been touched by fingers or has been soaked in water etc. then the cd will show corrupt on the computer because the information has been ruined.

The laser reflects in grooves that make 1's and 0's of Binary. Also the UMD is more like a DVD which stores more information than a normal cd.



psp888 - How come when I search cd or CD in the wiki search engine, it just says "Sorry, no results found for your query." even though the page is right here?

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