An uncorrectable error in a computer program can cause the program to crash, and if a disc containing such errors is used as a master for factory replication, the equipment at the mastering facility will abort when it sees the uncorrectable error. The mastering must then be redone, resulting in additional costs and delays in the replication job. Compact discs are composed of pits and lands that a CD-ROM drive or CD audio player reads and interprets to retrieve data or play audio. Many people believe, incorrectly, that the pits and lands represent the 1s and 0s that are ultimately interpreted as data or music. In reality, it is the transition between a pit and a land that represents a 0 or a 1.
Pits have different lengths and an ideal shape.
Variations in the shape of the pits and variation in the lengths of the pits can cause physical errors. Variations in the lengths and shapes of the pits on a CD are called pit length deviation and pit geometry, respectively. Pit length deviation means what it says. A pits on a CD needs to be one of nine different lengths. When a pit is not of the specified length for its class, errors can occur on the disc.