Hardware components of the PC
Storage devices
How information is stored on the compact disc

Information is stored in a spiral track contained on the top surface of the disc. The spiral track contains shallow depressions, called pits, in a reflective layer. Binary information is encoded by the lengths of these pits and the lengths of the areas between them, called land. During reading, a low power laser beam from the optical head is focussed on the spiral layer and is reflected back into the head. The ones bit is represented as the transition from pit to land or land to pit and the zeros bit as either constant pit or constant land.