Computers: From Mozart to Megabytes

Millions of music lovers have become addicted to the crisp, clear sound of the compact disc, which is rapidly replacing the records and cassette tapes in their collections. Now the CD seems destined to win the affection of computer buffs too. Inserted into a special disk drive connected to a personal computer, a single CD can deliver to the screen as much information as can be stored on 1,500 floppy disks. That is music to the ears of software manufacturers. Says Microsoft Chairman Bill Gates, who has spearheaded U.S. research in CD technology for computers: "The key is that the CD enables individuals to use a lot of information fast."

Microsoft underscored that point last week at an international CD conference in Seattle, where it introduced a $295 compact disc called Bookshelf. The title is most appropriate. The disc contains digitized versions of ten popular reference volumes, including Bartlett's Familiar Quotations, Roget's Thesaurus, the World Almanac and the U.S. Zip Code Directory. Equipped with a copy of Bookshelf, the special disk drive and a personal computer, a writer can have instant access to a wealth of reference material without interrupting word processing. With the push of a button, an individual can call up synonyms and quotations -- which pop up in "windows" on the screen -- and then, with another tap on the keyboard, insert them into the text.

The disc that stores music and data with equal ease is a technological marvel. Molded out of the same durable plastic used in bulletproof windows, the discs are engraved by laser beam, leaving microscopic "pits" and "lands" (flat areas) representing streams of binary digits. Each pit is no larger than a bacterium; some 2 billion fit on a 4.72-in. disc, laid down in a continuous spiral nearly three miles long. With this capacity, a single 4.72-in. disc can store up to 250,000 pages of text. And a CD surface area 6 ft. long and 6 ft. wide would be sufficient to store the words in every book ever written.

Book publishers were among the first to tap the CD's vast capacity. Two years ago, Grolier fit all 9 million words of its 20-volume Academic American Encyclopedia onto one-fifth of the surface of a single disc. Now some 130 different discs are available, including CD editions of such voluminous tomes as the Oxford English Dictionary, Books in Print and the Reader's Guide to Periodical Literature. The CD version of Census Bureau data enables anyone with a properly equipped personal computer to conduct demographic searches that once required a mainframe computer.

Despite their enormous potential, compact discs have some drawbacks. Unlike floppy disks, which can be erased and rerecorded at will, the compact discs now generally available are "read only" and cannot be altered outside the factory. Thus computer owners are unable to use the CDs to store their own data and programs or to alter those prerecorded on the disc. The same limitation affects software producers. Instead of updating its One Source disc of Wall Street data electronically, for example, Lotus must mail subscribers a new CD every week.