pasteboard-id
    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Specifies the pasteboard for which unsolicited input is being
    enabled. The pasteboard-id argument is the address of an unsigned
    longword that contains the pasteboard identifier.
    The pasteboard identifier is returned by SMG$CREATE_VIRTUAL_
    PASTEBOARD.
 AST-routine
    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       read only
    mechanism:    by value
    AST routine to be called upon receipt of unsolicited input at
    the terminal. The AST-routine argument contains the routine's
    procedure value. SMG$ENABLE_UNSOLICITED_INPUT detects the
    presence of unsolicited input and calls the AST routine with
    six arguments: the pasteboard-id, the AST-argument, R0, R1, PC,
    and PSL (on VAX systems) or PS (on Alpha systems).
 AST-argument
    OpenVMS usage:user_arg
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    A value to be passed to the AST routine. The AST-argument
    argument contains the value to be passed to the AST routine.