Fortran 90 I/O Considerations

Fortran 90 2.0 and FORTRAN 77 5.0 are I/O compatible. Executables containing intermixed f77 and f90 compilations can do I/O to the same unit from both the f77 and f90 parts of the program.

However, Fortran 90 provides some additional features:

• A file opened with FORM='BINARY' enables nonstandard I/O of raw data without record marks. This has nearly the same effect as FORM='UNFORMATTED', except that no record lengths are embedded in the file. As a result, it is not possible to backspace a FORM='BINARY' file. A READ statement on such a 'BINARY' file reads as much data as needed to fill all the variables on the input list.

• ADVANCE='NO' enables nonadvancing I/O, as in:

  ---

         write(*,'(a)',ADVANCE='NO')  'Enter size= '
         read(*,*) n

  ---

• NAMELIST input features:

  • f90 allows the group name to be preceded by $ or & on input. The Fortran 90 standard accepts only & and this is what a NAMELIST write outputs.

  • f90 accepts $ as the symbol terminating an input group unless the last data item in the group is CHARACTER, in which case the $ is treated as input data.

  • f90 allows NAMELIST input to start in the first column of a record.

• ENCODE and DECODE are recognized and implemented by f90 just as they are by f77.