ISO/IEC 1539 is a multipart International Standard; the parts are published separately. This publication, ISO/IEC 1539-1, which is the first part, specifies the form and establishes the interpretation of programs expressed in the base Fortran language. The purpose of this part of ISO/IEC 1539 is to promote portability, liability, maintainability, and efficient execution of Fortran programs for use on a variety of computing systems.