Effort of a NASA-sponsored, computer-based pro gram on "Modeling and analysis of Power Processing Systems" is reported. The overall program objec tive is to provide an engineering tool to reduce the design, analysis,and development time, and thus the cost, in achieving the required perform ance for power processing equipment and systems. Program philosophy, structures, and design and analysis examples are given to illustrate the program's utility in power and control circuit design, analysis, and optimization.