open reel - Computer Definition
A reel of magnetic tape. It typically refers to half-inch open reels that still remain in the archives of many data libraries. In the 1950s, before the 8-bit byte, 7-track tapes (seven parallel tracks) were used to accommodate a 6-bit character plus parity. Starting in the 1960s, 9-track tapes were used to support the byte. See half-inch tape and magnetic tape.