Check that the ID is not NIL and that it pertains to a primitive item.
Repeat
{
Read the modified count for this item.
Copy as many dimensions as there is room for in the user's buffer from the noticeboard and
return the actual number of dimensions in the item.
Read the modified count for this item once more.
}
Until time out or the two modified counts are equal and even
(which means that the values were not updated whilst they were being read).
If CHECK_MODIFY is FALSE, the item's modified count is not checked at all and a timeout cannot occur.
Note also that the MAXDIMS parameter to this routine is a MODIFIED parameter.
NBS__NILID NIL ID
NBS__NOTPRIMITIVE Item is not primitive
NBS__TIMEOUT Timeout awaiting valid data
NBS The Noticeboard System