Open reel refers to magnetic tape coiled in a reel. The drives have two spindles; one for the supply reel and another for take-up. Open reels gave way to self-threading tape cartridges, which contain both reels (see magnetic tape).Starting in the 1950sThe first computers used open reel half-inch digital tapes with seven parallel tracks that stored a 6-bit character plus parity. Starting in the 1960s, 9-track tapes supported the 8-bit byte and parity. Also in the 1950s, consumers began using quarter-inch open reel tapes for recording analog audio. See half-inch tape, magnetic tape and byte.