Fortran-90 array expressions and assignments. Array intrinsics defined in Fortran-90. Array library functions defined in the HPF library. There are other directives, including dynamic versions of the above. In the message passing model, parallel processes do not have direct access to each others' local memory.
Collective communication involves every process in a specified group .
PVM supports heterogeneity at the application, machine, and network level. PVM has libraries that contain routines for initiating processes on other machines, for communicating between processes, and changing the configuration of the virtual machine. PVM provides interfaces to programs in C and Fortran. Multiple users can configure overlapping virtual machines. However, recent versions e.g. Cray T3D avoid this.