IMAGINE holding the entire maintenance manual for a Boeing 757 aircraft - 7 feet of heavy books, weighing 140 pounds in total - in one hand. Now imagine being able to find every paragraph in the manual's 13,600 pages that contains the words ``auto pilot'' and ``flaps.'' Imagine finding the paragraphs in less than a minute. High-speed access to massive amounts of information is what the CD-ROM (compact-disc read-only memory) is all about. Compact discs, used mostly for music today, are beginning to be used to store information for computers. The entire 757 manual fits comfortably on one CD-ROM, with room to spare for another four copies.
One 4.7-inch disc can store 150,000 to 250,000 pages of information, depending on how it is arranged. That's 1,500 times as much as a conventional floppy disk, enough space to store the complete Oxford English Dictionary, 12 English-to-foreign-language dictionaries, or the 300 phone books listing everyone living in New York and New England.
CD-ROMs containing these data bases, as well as many others, were on display last month at the second CD-ROM Expo in Chicago. Nearly 1,400 people gathered here to discuss the growing uses of this new technology. While 1,400 people may not seem like a lot, it's four times last year's attendance of 316.
The United States market for CD-ROM goods and services is growing nearly as fast. It is expected to reach $197.3 million this year, up from $83.3 million in 1987, according to Link Resources, a New York-based research and consulting firm.
Next to business, libraries and education have been the largest CD-ROM markets. ``Six hundred megabytes is a vast amount of material to supplement textbooks and address the needs of advanced students,'' says Carolyn J. Kuhn, president of the Software Mart, an Austin, Texas-based producer of educational CD-ROM products for major publishers.
``That can all reside on a desktop. You don't need to have access to huge university libraries or forums of experts on a subject,'' she says.
One high school that has made CD-ROMs available to its students is the Illinois Mathematics and Science Academy, a state-sponsored boarding school for 510 of the state's ``gifted'' sophomores, juniors, and seniors.
Students ``use [CD-ROM] a lot for searching academic indexes,'' says Martha C. Guarin, the school's head librarian. Using a CD-ROM journal index, a student can locate in seconds all of the articles published in recent years on any topic in science, medicine, art, or general interest.
Students use the CD-ROMs ``because its so quick,'' Ms. Guarin says. ``Nobody's search lasts more than five minutes. The kids love it, they lap it up. It's easy to learn, and it's so fast that if they make a mistake they can just ask again.''
``The faculty use Books in Print for figuring out what to buy,'' she adds, referring to a CD-ROM version of the standard directory of all available books. With it, a teacher can type a few words and pull up a list of every book that has those words in its title.
CD-ROM players, which are normally used in conjunction with a personal computer, are popping up in libraries, universities, and businesses across the country. There are some 50,000 players in the US today. Nine hundred sixty CD-ROM titles were published in 1987 and 195,000 discs were replicated, according to Link Resources, which estimates that the market will reach 10,500 titles, 35 million discs, and $2.25 billion by 1992.
Scientists are using CD-ROMs to replace magnetic tapes for distributing geophysical data. The US Geological Survey is distributing sonar pictures of the sea floor on CD-ROM, as well as the last seven years of world seismic data from the National Earthquake Information Center, says Jerry McFaul, a computer scientist with the bureau. Each CD-ROM replaces 20 to 40 computer tapes: They're faster to read and cheaper to mail.
Because CD-ROMs hold so much, information that was too expensive to distribute just a few years ago is now becoming available. Space-Time Research, an Australian firm, has produced five CD-ROMs containing census data from the United States, Australia, New Zealand, Hong Kong, and Sweden.
``You can use it to produce maps'' containing information from the census, says Samantha Harvey, a consultant with the company. ``A table of numbers is really difficult to read, especially for people in an educational setting.'' One of Space-Time's discs is being used at the John Gardinar High School in Hawthorn, Australia, by students who produce maps for businesses and government departments.
``Someone comes to them and he wants to know where his potential clients are located,'' Ms. Harvey says, giving the example of a news distributor who is interested in carrying an Italian-language newspaper and wants to know where Italian-speaking residents are. Using the CD-ROM, students can make the businessman a map showing the concentration of Italian-speakers, accurate to within 200 households.
``When I was in school, if we wanted to do this we had to ring up the Bureau of Statistics. They would give us a whole stack of data. We had to sit with our calculators and do everything by hand, then we had to draw the map manually,'' she says. The computer, by contrast, automatically draws the map after reading the disc.
``You can spend more time actually analyzing the data rather than putting it together in the first place,'' she adds.
CD-ROM applications can combine information with CD-quality sound for exciting possibilities. There can be, for example, ``several language versions of the same material on the same disc,'' Kuhn says.
``You can have multilingual materials and particularly sound. Not synthesized sound - digitized sound,'' that sounds just as good as music off the very best CDs. Kuhn says sound is important, ``because inflection and pronunciation are critical to understanding and conveying meanings in foreign language.''
Nevertheless, CD-ROM comes a high price tag. Most discs cost more than $500 - the NYNEX phone book costs $10,000 a year - and the players cost between $600 and $1,000. Because of this, the largest number of CD-ROM users today are businesses.
Nearly one-quarter of all CD-ROM revenues generated last year came from one product, Lotus One Source, a data base of current financial information that features new discs weekly shipped via Federal Express at a price of $7,000 to $50,0000 a year, depending on the number of data bases subscribed to.
Large corporations are using the discs internally to distribute large data bases such as phone books, customer lists, or parts catalogs to branches. CD-ROMs let companies ``start providing access to information they couldn't get to before because of the cost'' of distributing the data, says John C. Ryan, who manages CD-ROM sales for Discovery Systems, a CD-ROM manufacturer.
``I don't think it's ready for the masses,'' says Barry Cinnamon, president of the Bureau of Electronic Publishing, which markets CD-ROMs and applications to consumers. ``But we're getting there. The `Constitution Papers' and the Bible together cost $80. But [consumers] still have to spend $600 on the drive'' required to read the discs.
A narrow track of 552 million letters
How does a CD-ROM (compact-disc read-only memory) hold so much?
CD-ROMs store information the same way musical CDs do: Information is converted to a stream of 1's and 0's, which is then converted to a series of pits and flat spots on a reflective surface inside the disc. The pits are very small: 0.6 microns in width, less than a quarter-millionth of an inch. Indeed, the pits are only slightly larger than the rays of light used to scan them.
The pits on a CD-ROM are arranged in one narrow, spiraling track. There are 16,000 tracks per inch on a CD-ROM, compared with 96 tracks per inch on a magnetic floppy disk. If the CD-ROM track could be unwound, it would be more than 3.5 miles long.
The disc spins at 200 to 500 revolutions per minute, spinning more slowly on the outside. The CD-ROM drive follows the track with a laser beam. When the laser hits a flat spot, the beam is reflected back and counted as a 1. When the laser hits a pit, it is scattered away and counted as a 0.
In total, the disc holds 552 million letters - enough to allow Northern Telecom to use one 4.7-inch disc to replace 40 feet of manuals for its DMS-100 and SL-100 telephone switches.
Saving paper saves money: Northern Telecom sells the paper version of its manuals for $21,000, but the CD-ROM version costs only $4,000, according to Edward J. Deveau, the company's director of strategic marketing for customer information services.
CD-ROMs also save trees.