Due to external influences and the imperfection of physical devices, errors can occur in data representation and data transmission. This chapter examines some methods of limiting the effect of errors in data representation and transmission. Error control coding should protect digital data against errors which occur during transmission over a noisy communication channel or during storage in an unreliable memory. The last decade has been characterized not only by an exceptional increase in data transmission and storage requirements, but also by rapid developments in microelectronics providing us with both a need for, and the possibility to, implement sophisticated algorithms for error control.