Fortran 90 definition
(Previously "Fortran 8x" and "Fortran Extended") An extensive enlargement of Fortran 77
. Fortran 90 has derived types, assumed shape arrays, array sections, functions returning arrays, case statement, module
subprograms and internal subprograms, optional and keyword subprogram arguments, recursion
, and dynamic allocation. It is defined in ISO 1539:1991, soon to be adopted by ANSI
["Fortran 90 Explained", M. Metcalf et al, Oxford University Press 1990].