Technological trends are extrapolated to the end of this century. Problems of utilizing high levels of integration are noted, and the capabilities of technology are viewed in the perspective of the problems to provide a forecast of the levels of integration that will be found in large computing systems. A physical model and some more speculative system assumptions are used to estimate the performance of the systems. The physical characteristics forecast for the system are summarized. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.