is set to the current advisory message unit number.
Note that Fortran unit numbers must be positive or zero. If
nadv is set
, output of advisory messages is totally suppressed. It is important to note that if you supply an illegal value for
nadv (such as a unit number associated with a file opened for reading instead of writing) then
x04abf cannot detect that fact, but any output sent to the unit by later calls of NAG routines may have undesirable consequences, such as program crashes.