ABSTRACT
Simulation programs are accepted as flexible and powerful tools for analyzing dynamical systems. The price to be paid is that simulation is mainly used for analysis and for design. Simulation can be considered as making several experiments with results that depend only on the model but also on the simulation experiment itself. A major change in simulation software, and so for PSI, has posed by the introduction of the IBM PC in the beginning of the eighties. Compared with other simulation programs, PSI always has offered an attractive graphics environment. Many simulation programs first calculate the responses and display, afterward, the responses on the screen. The program has been adapted to new developments, both in hardware and software. Although PSI is called a block-oriented simulation program, it exhibits nearly all the characteristics of an equation-oriented simulation language. Block names are used both to define the topology of the model and the value of the output of a block.
