A type of error-correction scheme named for its inventor, Richard Hamming, who worked at Bell Labs in the 1940s on the Model V relay-based computer. He developed his error-correction ideas in 1949 and first published them in 1950. Hamming codes are commonly used in telecommunications and in computer RAM. They are binary–linear codes that use seven bits to represent four bits of data; the additional three bits are for parity checking. Hamming codes can detect two errors, but can only fix a single error.