The primary computer storage media. The choice depends on accessing requirements. Disk is direct; tape is sequential. Locating a program or data on disk takes a fraction of a second. On tape, it can take several seconds or even minutes. Tapes have traditionally been used for backup and archival storage, and tape libraries with robotic mechanisms are common in large enterprises. In the 1980s and 1990s, small tape drives were sometimes used for desktop computer backup but were eclipsed by Zip disks and other magnetic media. After the turn of the century, CD-Rs, DVD-Rs and USB drives became the backup media for personal computers. The Future - Obsolete In time, magnetic media will be as obsolete as punch cards, when a solid state technology with no moving parts supersedes them. Considering the magical technology within the chip, hunks of metal and plastic whirling around a read/write head are rather archaic by comparison. See magnetic disk, magnetic tape, optical disc, HSM and early direct access devices.