How do rewritable CDs work?

A normal CD has a surface covered in microscopic bumps; a bump will signify a ‘0’ and a flat will signify a ‘1’ in the binary system and this is how data is read. This has to be different for a rewritable disc though. For this a dye is used to coat the surface. When writing on the CD the dye will either be opaque or clear with the two states representing the binary number system. The dye is designed to change between opaque and clear so the disc can be rewritten several times.

Answered by Claire Butler.