Object-oriented Scientific Programming with Fortran 90

Fortran 90 is a modern language that introduces many important new features beneficial for scientific programming. While the array-syntax notation has received the most attention, we have found that many modern softaware development techniques can be supported by this language, including object-oriented concepts. While Fortran 90 is not a full object-oriented language it can directly support many of the important features of such languages. Features not directly supported can he emulated by software constructs. It is backward compatible with Fortran 77, and a subset of HPF, so new concepts can be introduced into existing programs in a controlled manner. This allows experienced Fortran 77 programmers to modernize their software, making it easier to understand, modify , share, explain, and extend. We discuss our experiences in plasma particle simulation and unstructured adaptive mesh refinement on supercomputers, illustrating the features of For-tran 90 that support the object-oriented methodology. All of our Fortran 90 programs achieve high performance with the benefits of modern abstraction modeling capabilities.