Compact Disks: A StorehouseFor Text, Sound, Video Images
The compact disks used in the cd\rom format are essentially the same as those that largely have replaced phonograph records.
The surfaces of the disks are embedded with thousands of microscopic pits from which sound, text, data, and still and video images are retrieved by a scanning laser beam.
As a storage medium, the disks also have a number of advantages over the conventional floppy disks that currently are standard on nearly all microcomputers.
For example, one 4.75-inch compact disk is capable of storing as much information as 825 floppy disks.
And, while conventional hard drives in many computers are capable of storing equivalent amounts of information, they are not, like compact disks, readily portable.
Floppy disks are by nature susceptible to wear during use and are easily contaminated by dust and dirt.
But because the information stored on the cd is protected by a plastic coating and retrieved by a light beam, the likelihood of wear and damage is minimal.
The disks also are far more flexible in the types of data they are capable of storing.
A single disk can hold a computer-software program as well as film segments.
The disks do, however, have their own limitations.
"Full-motion video" images, for example, require large amounts of memory.
And the way the disks are manufactured makes it impossible for users to record their own data.
Some of the features of compact disks make them competitive with videodisks, which work on similar principles to store video programming, and which are also becoming popular with educators.
Some experts, such as Mary Budd Rowe, a professor at the University of Florida, argue that as the techniques for storing video on compact disks improve they eventually may replace videodisks.
Others, however, maintain that separate niches for both products exist in the market.
James Mecklenburger, executive director of the National School Boards Association's Institute for the Transfer of Technology to Education, says that just as several distinct types of magnetic recording tape are available for specific needs, so too will different optical storage devices be used for different purposes.
Meanwhile, at least one company, Pioneer Communications--the nation's largest producer of videodisk players--recently introduced a hybrid of the two media, called ld\rom.--pw