PVM (Parallel Virtual Machine) is a portable message-passing programming
system, designed to link separate host machines to form a virtual machine
which is a single, manageable computing resource.

The virtual machine can be composed of hosts of different architectures,
located in physically remote locations.  PVM applications can be composed
of any number of separate processes, or components, written in a mixture
of C, C++, and Fortran.  The system is portable to a wide variety of
architectures, including workstations, multiprocessors, supercomputers,
and PCs.