Data on the Disc

O Data is written to an optical disc in one of two ways: O With read-only optical discs, the surface of the disc is moulded or stamped appropriately to represent the data. O With recordable or rewritable optical discs, the reflectivity of the disc is changed using a laser to represent the data. O In either case, the disc is read with a laser and the computer interprets the reflection of the laser off the disc surface as 1s and 0s.
Data on the Disc O With moulded or stamped optical discs, tiny depressions or bumps are created on the disc’s surface called pits. O The areas on the disc that are not changed are called lands. O The transition between a pit and land represents a 1. O When the disc is read, the amount of laser light reflected back from the disc changes when the laser reaches a transition between a pit and a land.
Data on the Disc O In Recordable disc, the recording laser beam changes the reflectivity of the appropriate areas on the disc to represent the data stored there. O Dark, non-reflective areas are pits; reflective areas are lands. O The transition between a pit and a land still represents a 1 and no transition represents a 0.