A) Binary polynomial. Used to generate cheque information on blocks of data. Similar to a checksum, but is harder to generate and more reliable. b) Used in data transfer to cheque if the data has been corrupted. It is a cheque value calculated for a data stream by feeding it through a shifter with feedback terms “EXORed” back in. A CRC can detect errors but not repair them, unlike an ECC, which is attached to almost any burst of data that might possibly be corrupted.

CRCs are used on disks, ITU-R 601 data, Ethernet packets, etc.