New memory technologies.

Computers today use a hierarchy of large-capacity, relatively slow mechanically accessed memories in conjunction with fast electronically accessed memories of relatively small capacity. While the gap between these is spanned by ingenious organizations and programming, it would be highly desirable to fill it instead by some device of sufficient capacity and speed. Candidates for gap-filling memories include metal oxide semiconductor (MOS) random-access memories (RAM's) made by large-scale integration (LSI); charge-coupled devices; magnetic bubble devices based on cylindrical domains of magnetization; electron beam-addressed memories; and optical memories based on lasers, holography, and electrooptical effects. At present, the MOS RAM is the prime contender. Its natural evolution and the evolution of magnetic-recording techniques on which mass storage is based are likely to continue to shape the future as they have for more than a decade. On the other hand, radically new technologies, still at an early laboratory stage, are aimed at a more ideal solution than today's hierarchy.