[Pie]

Originally Posted by richlevy

I thought about that, but on Wiki they don't make the distinction and I'm not sure from my reading if that has always held true. Of course, most optical media is referred to by name (CD, DVD), so it's hard to judge. I'm a big fan of Terry Pratchett's Discworld series, so I've always wondered if it's a British variant thing, like colour instead of color.

Well, here's another wiki source [em is mine]:

By the 20th century, the c-spelling was more popular in British English, while the k-spelling was preferred in American English. In the 1950s, when the American company IBM pioneered the first hard disk drive storage devices, the k-spelling was used. Consequently, in computer jargon today it is common for the k-spelling to refer mainly to magnetic storage devices (particularly in British English, where the term disk is sometimes regarded as a contraction of diskette, a much later word and actually a diminutive of disk). Disc may also be spelt disque in certain regions (notably those with another minority language such as Wales, France or Ireland).
Some latter-day storage device manufacturers prefer the c-spelling. In 1979 the Dutch company Philips, along with Sony, developed the compact disc medium; here, the c-spelling was chosen. The c-spelling is now used consistently for optical media such as the compact disc and similar technologies.[3]