Interactive simulation on minicomputers : Part 1- ISIS , a CSSL language

Continuous System Simulation Languages (CSSLs) are used to program the simulation of dynamic systems that are described by differential equations. Mini computer-based languages are particularly attractive because they generally provide good man-machine interaction. This paper describes an interactive simulation language, ISIS, which provides many of the facilities hitherto restricted to large computers. ISIS is written in FORTRAN and can easily be imple mented on any computer that accepts FORTRAN IV pro grams (the original version runs on a PDP-8). ISIS is designed to offer the user high-level language facilities in the simplest possible form. Line-by- line syntax checking and the built-in editor allow fast interactive development of programs. The execu tion of a simulation can be interrupted by using special commands that allow the user to change the values of variables, modify or introduce OUTPUT and incremental PLOT statements, and produce 'post-mortem' graphs before continuing the simulation. With these and other interactive features, ISIS provides com prehensive facilities for the study of dynamic sys tems on modest minicomputer configurations.