Compiling Fortran 90 or Fortran 95 programs

The f90, xlf90, xlf90_r, and xlf90_r7 commands make your programs conform more closely to the Fortran 90 standard than do the other invocation commands. The f95, xlf95, xlf95_r, and xlf95_r7 commands make your programs conform more closely to the Fortran 95 standard than do the other invocation commands. f90, xlf90, xlf90_r, xlf90_r7, f95, xlf95, xlf95_r, and xlf95_r7 are the preferred commands for compiling any new programs. They all accept Fortran 90 free source form by default; to use them for fixed source form, you must use the -qfixed option. I/O formats are slightly different between these commands and the other commands. I/O formats also differ between the set of f90, xlf90, xlf90_r, and xlf90_r7 commands and the set of f95, xlf95, xlf95_r, and xlf95_r7 commands. We recommend that you switch to the Fortran 95 formats for data files whenever possible.

By default, the f90, xlf90, xlf90_r, and xlf90_r7 commands do not conform completely to the Fortran 90 standard. Also, by default, the f95, xlf95, xlf95_r, and xlf95_r7 commands do not conform completely to the Fortran 95 standard. If you need full Fortran 90 or Fortran 95 compliance, compile with any of the following additional compiler options (and suboptions):

-qnodirective -qnoescape -qfloat=nomaf:rndsngl:nofold -qnoswapomp
-qlanglvl=90std
-qlanglvl=95std

Also, specify the following runtime options before running the program, with a command similar to one of the following:

export XLFRTEOPTS="err_recovery=no:langlvl=90std"
export XLFRTEOPTS="err_recovery=no:langlvl=95std"

The default settings are intended to provide the best combination of performance and usability. Therefore, it is usually a good idea to change them only when required. Some of the options above are only required for compliance in very specific situations.

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