The Free On-line Dictionary of Computing (30 December 2018):

Fortran 90

   (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].

   (1994-12-16)