Optical discs are the state of the art in computer memory and storage, using lasers to record and retrieve information. Like magnetic discs, they can store many different kinds of information--sound, text, and pictures (both still and animated)--on the same disc. However, optical discs are far superior to their magnetic counterparts because they hold more data and, because the laser cannot damage the disc, they are more durable.

IBM began the first experiments with optical technology in the mid-1960s but made little progress until the semiconductor was developed. Sony and Philips saw the potential that the technology offered, and the two joined forces later in the decade, hoping to find a viable application for it. The result, in the 1970s, was the videodisc, which use a laser stylus to play back analog (as opposed to digital) information recorded in spiral tracks on a plastic...