Disk versus disc
Both spellings are correct, but are used for different types of media. The spelling "disk" is used for magnetic media such as hard drives. The spelling "disc" is used for optical media such as CDs and DVDs. IBM invented the hard disk drive and went with the spelling of "disk". When Philips invented the Audio Compact Disc they choose the spelling "disc".
IBM introduced the IBM 350, the first hard disk storage system, to the public on September 13, 1956. In March 1973 IBM introduced the 3340 Direct Access Storage Facility disk system for their IBM System/370 computer. The initial design had two 30 megabyte spindles. Kenneth E. Haughton, the leader of the 3340 development team, reportedly said, "If it's a 30-30, then it must be a 'Winchester'."