Fortran 90 offers significant enhancements to FORTRAN 77. Some of the features of Fortran 90 were implemented as language extensions in earlier versions of Compaq (formerly DIGITAL) Fortran.
Certain features of FORTRAN 77 have been replaced by more efficient statements and routines in Fortran 90. These features are listed in Obsolescent Features.
Although most FORTRAN 77 functionality remains unchanged in Fortran 90, some features need special handling. For more information on building Fortran programs, refer to Compatibility Information.
Fortran 90 features are described in the following sections: