POPLOG ' sTwo - level Virtuol Mochine Support for lnteroctive Longuoges

Poplog is a portable interactive AI development environment available on a "ur}g" of op""ating systems and machines. It includes incremental compilers for bommon Lisp, Pop-ll, Prolog and Standard ML, along with tools for adding new incremental compilers. All the languages share a common development environment and data structures can be shared between programs written in the different languages. The power and portability of iroptog depend on its two virtual machines, a high level virtual machine tpWf-tne Poplog Virtual Machine) serving as a target for compilers for interactive languages and a low level virtual machine (PIM-the Poplog Implementation Machine) as a base for translation to machine code. A machine-independent and language-independent code generator translates from the PVM to thePIM, enormously simplifyingboththe taskofproducing a new compiler and porting to new machines.