depadr

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Depth to which the procedure call stack is to be unwound. The
    depadr argument is the address of a longword value. The value 0
    specifies the call frame of the procedure that was executing when
    the condition occurred (that is, no call frames are unwound); the
    value 1 specifies the caller of that frame; the value 2 specifies
    the caller of the caller of that frame, and so on.

    If depadr specifies the value 0, no unwind occurs and $UNWIND
    returns a successful condition value in R0.

    If you do not specify depadr (or with some languages you specify
    an address of 0), $UNWIND unwinds the stack to the call frame
    of the procedure that called the procedure that established the
    condition handler that is calling the $UNWIND service. This is
    the default and the normal method of unwinding the procedure call
    stack.

 newpc

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    New value for the program counter (PC); this value replaces the
    current value of the PC in the call frame of the procedure that
    receives control when the unwinding operation is complete. The
    newpc argument is a longword value containing the address at
    which execution is to resume.

    Execution resumes at this address when the unwinding operation is
    complete.

    If you do not specify newpc, execution resumes at the location
    specified by the PC in the call frame of the procedure that
    receives control when the unwinding operation is complete.