Computer disks known as CD-ROMs store vast amounts of data and often come with equally big price tags: Since there has been no way to track how much data will be used, CD-ROM publishers have charged for everything on a disk. But not for much longer. Cryptologics Inc. in New York City has developed a meter that gauges data use just as an electric meter tracks power demand.
The system depends on a decryption program, installed on the disk, that keeps track of how much data is decoded, then subtracts its cost from a prepaid credit. Cryptologics head Peter J. Sprague, who is also chairman of National Semiconductor Corp., is working initially with Mead Data Central Inc., which owns the Lexis legal data base. Cryptologics proposes to store the Lexis data that's most often used on CD-ROMs, thus easing the strain on Mead's mainframes. It will charge as little as $10 per disk, keep 30% of the usage fee, and pay Mead the rest. The first product may arrive early next year.