This report gives complete documentation for a working implementation of a discrete, event driven Smalltalk-80 modelling context described in Goldberg and Robson "Smalltalk-80: The Language and its Implementation". It also documents DEMOS-derived enhancements to this simulation system and methods for improved presentation of results. The system is running under Apple's level0 image on a Macintosh plus computer. It uses only standard Smalltalk-80 and will be portable to any other standard Smalltalk system. An extremely brief introduction to Smalltalk, source code and example programs are given as appendices.