The PVM system is composed of two parts. The first part is a daemon, called pvmd3, that resides on all the computers making up the virtual computer. (An example of a daemon program is sendmail, which handles all the incoming and outgoing electronic mail on a Unix system.) pvmd3 is designed so that any user with a valid login can install this daemon on a machine. When a user wishes to run a PVM application, he executes pvmd3 on one of the computers which in turn starts up pvmd3 on each of the computers making up the user-defined virtual machine. A PVM application can then be started from a Unix prompt on any of these computers.
The second part of the system is a library of PVM interface routines. This library contains user-callable routines for passing messages, spawning processes, coordinating tasks, and modifying the virtual machine. Application programs must be linked with this library to use PVM.