Seagate Technology PLC is an American data storage company that was incorporated in 1979 as Shugart Technology. It is currently incorporated in Dublin, Ireland and has its principal executive office in Cupertino, California, USA.Seagate developed the first 5.25-inch hard disk drive (HDD) in 1980, the 5-megabyte ST-506. Major supplier in the microcomputer market during the 1980s.