A multi-language programming environment, which includes the languages Pop-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)].