The Beeb in school in the 80s had a 5¼-inch floppy disc drive. The BBC Domesday project, 84-86, was on Lazer Disc. But as Compact Discs took flight in the domestic market we'd moved to 3½-inch floppy disks; which by the 90s were labelled "diskette" IIRC and so were called disks. Then hard drives were called hard disk drives I think because they came from the global/USA market, so the only "discs" that remained in common use were optical discs, and the split - for me at least - was kinda-retconned in that optical discs were always 'discs' and magnetic were always 'disks'.
I think it's both, in the UK at least.
The Beeb in school in the 80s had a 5¼-inch floppy disc drive. The BBC Domesday project, 84-86, was on Lazer Disc. But as Compact Discs took flight in the domestic market we'd moved to 3½-inch floppy disks; which by the 90s were labelled "diskette" IIRC and so were called disks. Then hard drives were called hard disk drives I think because they came from the global/USA market, so the only "discs" that remained in common use were optical discs, and the split - for me at least - was kinda-retconned in that optical discs were always 'discs' and magnetic were always 'disks'.
The early UK made hard disk drives were [sometimes?] called "disc drives", http://www.computinghistory.org.uk/det/22567/%20Acorn%20BBC%... this one from Cumana, Guildford, UK, http://www.computinghistory.org.uk/det/36026/Cumana%205.25-i... says "disk drive" though, and I'm shocked ;o) ...