Abstract
This thesis analyzes the performance improvements achieved by distributing text editing software between a dedicated microprocessor and a timeshared host computer. Theoretical analysis of the problem coupled with detailed simulations of possible architectures, using data collected from over 15,000 actual editing sessions, provide strong evidence that simple, easily implemented schemes produce significant improvements of response time to user commands, communications bandwidth requirements, and host CPU utilization. Consisting of an editor server program running on a host and a local editor running on a microprocessor, a distributed editor would a) provide general, flexible editing capabilities that are functionally indistinguishable from those of conventional video editors, b) provide the same average response on 1200 baud communications lines as conventional editors running at 9600 baud, c) isolate the user from most delays due to host timesharing pauses and communications network slowdowns, and d) reduce considerably the number of program activations and CPU cycles at the host, making distributed video editors consume fewer host resources than conventional line editors. The implementation of a prototype distributed editor based on the conclusions of the study demonstrates the practicality of implementing the required software on existing, inexpensive microprocessors such as those found in conventional terminals.