Group coded recording was first used for magnetic tape data storage on 9-track reel-to-reel tape. The term was coined during the development of the IBM 3420 Model 4/6/8 Magnetic Tape Unit and the corresponding 3803 Model 2 Tape Control Unit, both introduced in 1973. IBM referred to the error correcting code itself as "group coded recording". However, GCR has come to refer to the recording format of  bpi (250 bits/mm) tape as a whole, and later to formats which use similar RLL codes without the error correction code.