Birtwistle, Graham2008-02-272008-02-271981-11-01http://hdl.handle.net/1880/45703This paper covers the design and implementation of the latest Simula based package for discrete event simulation modelling. Demos inherits Simula's process approach and provides additional features for handling process synchronisations and interrupts, (unobtrusive) data collection, automatic tracing and reporting, and for the automatic generation of well-separated seeds in the random number routines. This paper outlines the implementation of these facilities and gives examples of how they can be used. It is written in five parts: part 1 introduces Simula; part 2 describes the process approach to discrete event modelling; part 3 compares that approach with the transaction, event and activity styles and gives implementation outlines of GPSS, Simscript, and ECSL in Simula; part 4 goes through the facilities contained in Demos and motivates them via examples; and part 5 is concerned with the implementation techniques involved.EngComputer Scienceunknown1981-72-2410.11575/PRISM/30370