ITT from Fraser-Nash

Abstract

EARLY DESIRE (Direct Executing SImulation in REal time) is the first of a series of entirely new floating-point equation-language systems for interactive continuous-system simulation. DESIRE systems combine high computing speed (1.3 to 4 times faster that threaded FORTRAN) with immediate direct execution: no external compiler, linker, or loader is needed. DESIRE employs an interpreted job-control language (essentially an advanced BASIC dialect) for slower operations such as interactive program entry, editing, file manipulation, and for programming multi-run simulation studies. The ‘dynamic’ program segment containing differential equations in first-order form is entered just like the BASIC statements and can freely access the same named variables. The relative simplicity of the time-critical dynamic segment permits us to compile it practically instantaneously into efficient machine code, since a simple, super-fast compiler will do. DESIRE utilizes existing, precompiled FORTRAN integration routines; different integration rules can be switched as disk overlays while the program runs. EARLY DESIRE runs on PDP-11 or LSI-11 mini/microcomputers. Future DESIRE systems will download dynamic program segments into a variety of multiple execution processors.Thereafter rose Desire in the beginning; Desire, the primal germ and seed of Spirit.