The width of the digital magnetic tape that became popular in the 1950s. More convenient as well as holding more data, half-inch self-threading tape cartridges began to replace open reels in the mid-1980s (see tape cartridge
Although storage capacity was limited to little more than a couple hundred megabytes per reel, a few legacy information systems using open reel tapes survived into the 21st century. See open reel
, magnetic tape
The Half-Inch Open Reel
Practically extinct today, half-inch open reels were the common means of computer storage from the 1950s to the 1980s.