Note that DBL_DIG is the number of decimal digits that can be a 9. If the max integral value storable in a double is 4,000,000, DBL_DIG would only be 6. It is a

Note that DBL_DIG is the number of decimal digits that can be a 9. If the max integral value storable in a double is 4,000,000, DBL_DIG would only be 6. It is a conservative limit.