Most parameters are associated with values of one type or another, e.g. primitive data types, or data-system objects. These are known as normal parameters.
However, there is a class of parameters which are intimately associated with some type of device (e.g. a magnetic tape drive, or a graphics terminal). These are known as device parameters. Device parameters are typically used in calls such as GKS_ASSOC. A parameter is defined as a device parameter by the PTYPE field.
where parameter-type is a character string which can currently only be DEVICE.PTYPE parameter-type
The precise type of the device can be indicated by the TYPE field. The specification for parameter DISPLAY in our example above would then be:
The value of a device parameter is a name which can be translated to define the device to be used. For details of possible values, see the appropriate facility description, SGS, GKS, FIO etc.PARAMETER DISPLAY . PTYPE DEVICE TYPE GRAPHICS . ENDPARAMETER
Currently PTYPE is not used by the system - only the TYPE is of significance and there anything other than a standard HDS type will have the same effect.
ADAM Interface Module Reference Manual