FILTER is the name of a logical function that is called for each workstation name in the list and can be used to select or reject workstations on criteria such as workstation class. It should return the value .TRUE. if the name is to be included in the list and .FALSE. if it should not. FILTER has one integer argument; the GKS workstation type.
The GNS library contains a suitable function called GNS_FILTG which rejects any workstations that are not supported by the copy of GKS being run (if GKS is open; if it is not all workstation types are selected).
GNS [2.5exrkstation