Optical disc

Flat, usually circular disc that encodes binary data

An optical disc is a flat, usually disc-shaped object that stores information in the form of physical variations on its surface that can be read with a beam of light. Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to be detected on the other side. They may contain analog or digital information, or a mixture of the two.

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