Fortran Standards Documents
Draft (unofficial) versions of the various recent Fortran standards and corrigenda are available from the J3 website, the WG5 website, and/or the WG5 file server, in various formats. In addition, some older Fortran standards are available from www.fortran.com. The official standards can be bought from the International Organization for Standardization (ISO) or from your national standardization organization.
Note that, of these standards, GNU Fortran currently only supports the base Fortran 95 standard (not parts 2 or 3) as amended in the two corrigenda, the Fortran 95 TR 15581 extension, the Fortran 77 standard with the MIL-STD 1753 extensions, and some portions of the Fortran 2003 standard; these standards have been highlighted in bold. The other documents are linked here for reference, but should not be taken as documentation of GNU Fortran features.
Fortran - Automatic Coding System for the IBM 704
The oldest version; dated October 15, 1956, first presented in February 1957 and first delivered in April 1957. Fortran - Programmer's Reference Manual (PDF)
(ISO Varying strings are not implemented in GNU Fortran, but Fortran 95 module exists which implements this is Fortran.)
(Conditional Compilation is not supported directly by GNU Fortran but you can preprocess the files using COCO.)
Fortran 95 Corrigendum 1, draft: (pdf)
Fortran 95 Corrigendum 2, draft: (pdf)
Fortran 2003 Corrigendum 4: PDF
Fortran 2003 Corrigendum 5: PDF
Fortran 2003 Corrigenda 1 to 5: combination of the corrigenda about - PDF
Fortran 2003 update pages (consists of corrigenda 1 and 2)
The new features of Fortran 2008 by John Reid (non normative)
TR 29113 Further Interoperability of Fortran with C
TR on further coarray features
Other Relevant Standards
OpenMP (Open Multi-Processing)
OpenMP specifications - for gfortran relevant and supported are 2.5 and 3.0.
The IEEE standard covering Fortran 77 POSIX bindings is available online, though unfortunately only from locations with appropriate subscriptions to the IEEE server (e.g., many university networks). For those who do have such access, the link is:
POSIX Fortran 77 Language Interfaces (IEEE Std 1003.9-1992) (pdf)
Note IEEE 1003.9-1992 was withdrawn 6 February 2003. Some vendors provide their own way to access POSIX functions and make those available as module; for instance the IFPORT module of Intel or the f90_* modules of NAG. There also some compiler-independent efforts to make them accessible, e.g. Posix90 (doc), flibs' platform/files and directories, fortranposix.
ISO/IEC Project 22.24772: Guidance for Avoiding Vulnerabilities through Language Selection and Use
"The OWGV project is preparing comparative guidance spanning multiple programming languages, so that application developers will be better able to avoid the programming errors that lead to vulnerabilities in these languages and their attendant consequences. This guidance can also be used by developers to select source code evaluation tools that can discover and eliminate coding errors that lead to vulnerabilities."
Draft N0138 (2008-08-18)
The IEEE Standard for Binary Floating-Point Arithmetic (IEEE 754) is the most widely-used standard for floating-point computation. Unfortunately, they are not freely available.
IEEE 754-1985 Standard for Binary Floating-Point Arithmetic
IEEE 854-1987 Standard for Radix-Independent Floating-Point Arithmetic
Latest publicly available draft of IEEE 754-2008 (4 October 2006)
ISO/IEC 9899 Programming languages -- C
The C standard is relevant for two parts: (a) the interoperability features of Fortran 2003/2008/interop TR and (b) for the C Preprocessor (CPP; "Preprocessing directives"), which gfortran supports as vendor extension.
'''JTC1/SC22/WG14''' - C (C drafts are also available there)