Open reel refers to magnetic tape coiled in a reel. The drives have two spindles; one for the supply reel and another for the take-up reel. Open reels gave way to self-threading tape cartridges, which contain both reels (see Magstar
Starting in the 1950s
The 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 open reel tapes, but they were quarter inch and for analog audio recordings. See half-inch tape
, magnetic tape
The supply reel is manually mounted on one spindle, and the loose end of the supply tape is threaded around a magnetic head and onto the empty take-up reel on the other spindle.
There Were Millions of Them
For more than 50 years, open reel tapes were used for data storage. For a short time after the turn of the century, half-inch open reel tape drives were still manufactured. Widely used computer standards hang around longer than one might think. (Bottom image courtesy of The Computer History Museum, www.computerhistory.org)