| CRC CRC is
a mathematical technique used to check for errors when sending data by
modem. Because some phone lines are notoriously crackly and can cause
breaks in transmission, this is a crucial step. If the CRC fails to add
up, the receiving end of a data transmission sends a NAK (negative
acknowledgement or "say that again") signal until it does add up. CRCs are
also used in tape backups and other streaming communications. |