The XL Fortran compiler helps you to port or to migrate source code among Fortran compilers by providing full Fortran 90 and Fortran 95 language support and selected language extensions (intrinsic functions, data types, and so on) from many different compiler vendors. Throughout this document, we will refer to these extensions as "industry extensions".
To protect your investment in FORTRAN 77 source code, you can easily invoke
the compiler with a set of defaults that provide backward compatibility with
earlier versions of XL Fortran. The xlf, xlf_r, f77, and fort77 commands provide maximum
compatibility with existing FORTRAN 77 programs. The default options
provided with the xlf90 and xlf90_r commands give access to the full range of Fortran 90 language
features. The default options provided with the xlf95 and xlf95_r commands give access to the full range of Fortran 95 language
features.