Direct-Executing Languages for Interactive Simulation and Computer-Aided Experiments

Summary

EARLY DESIRE (DirectExecutingSImulation inREal time) is a new floatingpoint equation-language Tor interactive continuous-system simulation on DEC PDP-11 or LSI-11 workstations. Programs run 1.3 to 5 times faster than threaded FORTRAN and execute directly on a typed RUN command; there is no visible compiler or linker. An interpreted job-control language provides interactive program entry, editing, and file operations and programs multi-run simulation studies. The “dynamic” program segment determining the simulation model is entered just like the job-control program and accesses the same named variables A small, very fast compiler translates the “dynamic” segment practically instantaneously before the first simulation run. Different precompiled integration rules may be overlaid from mass storage.

EARLY DESIRE can handle up to 40 state variables and provides a true CRT screen editor with cursor-control keys, a macro facility, and run-time graphics even on inexpensive alphanumeric terminals. The language admits subscripted variables and permits especially efficient simulation of sampled-data control systems. Future DESIRE systems will be written in standard PASCAL for machine independence and will run on 32-bit superminicomputers.