The Language Reference is part of a documentation suite that offers information on installing and using the IBM(R) XL Fortran compiler on Linux(R). This document defines the syntax, semantics, and restrictions you must follow to write valid XL Fortran programs.
Fortran (FORmula TRANslation) is a high-level programming language primarily useful for engineering, mathematical, and scientific applications involving numeric computations.
XL Fortran implements many Fortran 95, Fortran 2003, and other language specifications maintained by the ISO standards for the Fortran programming language, and also incorporates many extensions to the core language. These extensions have been implemented with the aims of enhancing usability in specific operating environments, assuring compatibility with other compilers, and supporting new hardware capabilities. In theory, a program that compiles correctly on one standards-conforming compiler will compile and execute correctly under all other conforming compilers, insofar as hardware differences permit.
The compiler detects most non-conformities to the XL Fortran language rules, but may not detect some syntactic and semantic combinations. The compiler cannot detect all combinations for performance reasons, or because the nonconformance is only detectable at run time. XL Fortran programs that contain these undiagnosed combinations are not valid, whether or not the programs run as expected.