Beyond desire: Pascal implementations of direct-executing simulation languages

Two new simulation languages, DESIRE P and DESCTOP, combine interpretation of the experiment protocol with fast compilation of the model differential equations and thus execute directly on a typed RUN command. Simulations run at about FORTRAN 77 speed. While earlier languages of this type (MICRODARE and DESIRE V3) were implemented in assembly language, both new systems are written in PASCAL except for FORTRAN integration routines and a small machine-language interface, so that the code was readily ported from the PDP-11 to the VAX. DESIRE P incorporates a new one-pass compiler and some precompiler syntax checking. DESCTOP is a general-purpose workstation language with complex arithmetic, matrix transformations, fast Fourier transforms, true procedures, and structured programming with automatic prettyprinting. Like DESIRE V3, both new languages permit convenient screen editing and contain operating-system commands and command procedures as a language subset. On the VAX, both languages support simulation with 100 or more state variables and Tektronix color graphics. An IBM PC/XT/AT version also exists.