An alphanumeric filing system uses both numbers and alphabetic letters to express a notion within an organisation. The classification system of the Library of Congress is one of the most common examples.
The Library of Congress classification system employs letters to identify certain classes of material and adds second letters, which denote subclasses, to further specify the subject matter. These subclasses are numbered and organised hierarchically from broad concepts to more particular circumstances.
Whether an alphanumeric filing system is suitable for the task relies on how the information is defined and whether the files must be organised in a particular way. For instance, the Library of Congress system is built to display subject linkages.