What is the purpose of a Cyclic Redundancy Check (CRC)?

A Cyclic Redundancy Check (CRC) is a mathematical algorithm used extensively in digital communications to verify data integrity. Before transmission, the sender calculates a short, fixed-length binary sequence based on the data packet and appends it to the end. Upon receiving the packet, the receiving station performs the exact same mathematical calculation. If the receiver's result matches the appended CRC, the data is considered valid. If it does not match, the receiver knows the data was corrupted during transit. It is crucial to differentiate between detection and correction. A CRC alerts the system that an error has occurred, but it lacks the information necessary to repair the corrupted bits. Therefore, it is strictly an error detection tool, not an error correction or compression technique.