Maintaining FORTRAN software by enforcing abstract data types

The principles of data abstraction facilitate maintenance and enhance software reliability. However, FORTRAN includes features that undermine data abstraction. A FORTRAN preprocessor called FAD enforces data abstraction when reusing FORTRAN-callable subprograms. Using FAD, reusable software is organized as the implementation of abstract data types (ADTs). FAD users access the reusable software by declarations and subprogram invocations based on the ADTs. The FAD preprocessor translates ADT references into FORTRAN code and prohibits inappropriate manipulation of ADT instances. With the FAD system, ADT implementations can be changed without changing FORTRAN code that uses the ADTs. A maintenance strategy using FAD facilitates detailed control of reusable software