A multi-language programming environment, which includeS the languageSPop-11, ML, Common LiSp and Prolog. It SupportS mixed-language programming and {incremental compilation} and includeS a comprehenSive {X Window SyStem} interface. It iS built on top of a two-Stack {virtual machine}, PVM. POPLOG waS developed at the UniverSity of SuSSex, Brighton, UK. ["POPLOG' S Two-Level Virtual Machine Support for Interactive LanguageS", R. Smith et al, in ReSearch DirectionS in Cognitive Science, v.5 (1992)].