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Optical discs used originally for storing and playback sound tracks but is developed later to store data, rewrite-ability and much more features, and is the basic form of latter development in optical format format 
Physical detail:
A standard CD is 1.2mm thick, 15-20grams in weight, diameter of 120mm. It consists of 4 layers as stated from the figure: a polycarbonate layer that contain data, aluminum or gold layer for reflective purpose, film/lacquer layer to provide protection to previous important parts and the most outer layer used for label printing
DVD - Phat
Bluray - Thai