CD-ROM is the offspring of video disc technology developed in the 1960s and early 1970s, before the advent of the home VCR. The goal was to store movies on the disc. Different companies have a number of methods for storing video signals, including the use of a needle to respond mechanically to grooves in a disc, much like vinyl LP record does. the consumer products industry spent a great deal of money developing the different technologies, including several approaches to optical storage. Then they spent years fighting over which approach should become standard. The surviving format is one called laser vision. By the time laser vision emerged as the winner, the competing developers had not only spent enormous sums of money but had also lost important market opportunities. These hard lessons were put to use in the subsequent development of CD audio and CD-ROM.
From the outset, there was an interest in using a laser vision discs to do more than just a record movies. The laser vision format supports recording in both a constant linear velocity (CLV) space format that maximizes storage capacity and a constant angular velocity (CAV) format that enables fast seek performance. By using the CAV format to access individual video frames quickly, a number of organizations, including MIT media lab, produced at a prototype interactive video discs that could used to teach and entertain.
In the early 1980s, a number of firms began looking at the possibility of storing digital, textual information all laser vision discs. Laser vision stores data in an analog form; it is, after all, storing an analog video signal. Different firms came up with different ways of encoding digital information in analog form so it could be stored on the disc. The capabilities demonstrated in the prototypes and early, narrowly distributed products were impressive. The videodisc has a number of performance characteristics that make it a technically more desirable media than the CD-ROM; in particular, one can build drives that seek quickly and deliver information from the disc at a high rate of speed. But, reminiscent of earlier disputes over the physical format of the videodisc, each of these pioneers in the use of laser vision discs as computer peripheral had incompatible encoding schemes and error correction techniques. There was no standard format, and none of the firms was large enough to impose its format over the others true sheer marketing muscle. Potential buyers were frightened by the lack of a standard; consequently the market never grew.
During this same period Phillips and Sony began work on its way to store music on optical discs. Rather than storing the music in the kind of analog form used on video discs, they developed a digital data format. Philips and Sony had learned hard lessons from the expensive standards battles over video discs. This time they worked with other players in the consumer products industry to develop a licensing system that resulted in. the emergence of CD audio as a broadly accepted, standard format as soon as the first discs and players were introduced. CD audio appeared in the United States in early 1984. CD-ROM, which is a digital data format built on top of the CD audio standard, emerged shortly thereafter. The first commercially available CD-ROM drives appeared in 1985.
Not surprisingly, the firms that were delivering digital data on laser vision discs saw CD-ROM as it a threat to their existence. They also recognized, however, that CD-ROM promised to provide what had always eluded them in the past; standard a standard physical format. Anyone with a CD-ROM drive was guaranteed that he or she could find and three sector off of any disc manufactured by any firm. For a storage medium to be used in publishing, standardization at such a fundamental level is essential.
What happened next is remarkable considering the history of standards and cooperation within industry. The firms that had been working on products to deliver computer data from videodiscs recognized that a standard physical format, such as that provided by CD-ROM, was not enough. A standard physical format meant that everyone would be able to read sectors off of any disc. .but computer applications to not more in terms of sectors; they store data in files. Having an agreement about finding sectors, without further agreement about how to organize the sectors into files, is like everyone agreeing on an alphabet without having settled on how letters are to be organized into words on a page. In late 1985 the firms emerging from videodiscs/digital data industry, all of which were relatively small, called together many of the much larger firms moving into the CD-ROM industry to begin work on a standard file system that would be built on top of the CD-ROM format. In a rare display co-operation, the different firms, large and small, worked out the main feature of a file system standard by early summer of 1986; that work has become an official international standard for organizing files on CD-ROM.
The CD-ROM industry is still young, though in the past years it has begun to show signs of maturity: it is moving away from concentration on such matters as disc formats were concerned with CD-ROM applications. Rather than focusing on the new medium in isolation, venders are seeing it is an enabling mechanism for new systems. As it finds more uses in a broader array of applications, CD-ROM looks like an optical publishing technology that will be with us over the long term.
Recordable CD drives make it possible for users to store information on CD. The price of the drives and the price of the blank recordable CDs make this technology very appealing for backup. Unfortunately, while the speed of CD readers has increased substantially, with 52X (52 times CD audio speed) as the current standard, CD recorders work on the same speed.
The latest technology for CDs is the DVD, which stands for digital video disc or Digital versatile disc. The Sony Corporation has developed DVD for the video market, especially for new high-definition TVs, but DVD is also available for storing files. The density of both tracks and bits has been increased to yield a sevenfold increase in storage capacity. DVD is also available in two sided medium that yields nearly 10 GB per disc.
