Like Vensim and Stella, Powersim is a visual software to help you conceptualize, build and test system dynamics models. Powersim is provided by the Powersim Corporation (1175 Herndon Parkway, Herndon, VA 20170) and is documented in the corporation's promotional and tutorial materials and their Reference Manual (Powersim Corp. 1996). The software is available at low cost for student use. If you wish to put your models to commercial use, Powersim Corporation provides a professional version with a wide array of supporting tools. You may also purchase the "Solver," a companion product to provide the "high end" analytical features of optimization and risk analysis. And Powersim provides "metro server," the application that allows simulation models to run remotely via an Internet or Intranet.

Unlike Vensim or Stella, Powersim does not provide "platform independence." If you want your models to be used on both Macintosh and IBM compatible computers, Stella or Vensim would be more suitable. Powersim is designed for IBM compatible computers and is normally used with the Windows operating system. For Windows users, Powersim is an excellent software for model building and testing. It is especially valued by Windows users in large organizations because of its connectivity tools:

DDE, Dynamic Data Exchange for both server and client exchange of data using standard Windows protocol,

OLE, Object Linking and Embedding to link objects (such as flow diagrams) across applications, and

API, Application Programmers Interface to allow programmers to connect Powersim simulations to Visual Basic and other applications.

The purpose of this appendix is to introduce Powersim using the sales force model shown previously. The example will reveal the fundamental similarity between Powersim and the previous visual stock and flow programs.