Data on Tape
The UNIVAC I (1951) started a new trend in data storage: magnetic tape. IBM soon began using reels of magnetic tape (similar to the audio tape of the time) for computer data storage, and the rest of the industry followed suit. Computer tape, usually stored in open reels, generally consisted of thin strips of plastic coated with a magnetically sensitive substance that computers wrote to and read from by means of electronic heads embedded in a special tape drive.
Numerous production computer models (especially mainframes and minicomputers) used open-reel tape as a mass storage medium until the 1970s and 1980s, when designers switched in increasing numbers to tape cartridges.
(Want to experience the UNIVAC for yourself? Try this simulator.)