The use of computers was challenged, until recently, by a simple yet seemingly insurmountable problem: the transmission of data between one fixed hard drive and another. Traditional methods, such as floppy and ZIP disks, have extremely limited capacity. These are appropriate only for smaller documents and files. They are also fragile and prone to data corruption, notably I/O (input-output) errors. These flaws make them inappropriate for the transfer of large--or important--files. Removable memory drives have the opposite problem--they, in a sense, are `overkill.' That is, they can hold massive amounts of data, but are large, expensive, and very fragile. Both disks and memory drives must be formatted to a specific computer manufacturer's specifications: a 3.5in floppy disk, formatted to IBM standards, is unreadable to an Apple machine. The development of the compact disc solved the problems of storage capacity and transferability of...