The compact disk ROM: How it works: An offshoot of the compact digital audio disk, this multimegabyte storage technique is revolutionizing database technology

A description is given of the CD-ROM, or compact-disk read-only memory, which is an offshoot of the highly successful digital compact disk (CD) used for audio recording. It is a permanent optical digital storage device that, in conjunction with an associated drive, becomes a powerful peripheral for the personal computer. The disk puts multimegabyte permanently stored databases at the user's fingertips. Compared with traditional mass-storage media, like magnetic tape, the CD-ROM has many advantages, the most important being high capacity and relatively low cost. A 120-mm-diameter CD-ROM can hold as much data as 1400 to 1700 standard 360-kilobyte diskettes for an IBM personal computer, or up to 120 magnetic disks 133 mm in diameter, bringing the cost of a system to 0.0001 cent per bit. The formatting of data to correct errors and the way in which lasers read the data are explained.