Standard music CDs. CD-DA became CD-ROMs when people realized that you could store 650 Mb of computer data on a 12-cm optical disc. CD-ROM drives are simply another kind of digital storage media for computers, albeit read-only. They are peripherals just like hard disks and floppy drives. (Incidentally, the convention is that when referring to magnetic media, it is spelled disk. Optical media like CDs, laserdisc, and all the other formats are spelled disc.) CDDI (Copper Data Distributed Interface)