g95 – Fortran 95 compiler

g95 is a free, portable, open source Fortran 95 compiler.

It implements the Fortran 95 standard, part of the Fortran 2003 standard and some old and new extensions including proposed features for the Fortran 2008 standard like Co-array Fortran.

Parts of the F2003 and F2008 standards have been implemented in g95.

Features include:

  • Operation of compiled programs can be modified by a large list of environment variables, documented in the compiled program itself.
  • TR15581– Allocatable dummy arguments, derived type components.
  • F2003 style procedure pointers, structure constructors, interoperability.
  • F2003 intrinsic procedures and modules.
  • Dummy arguments of type VALUE in subroutine are passed by value.
  • Comma option in OPEN, READ, and WRITE for denoting decimal point.
  • Square brackets [ and ] may be used for array constructors.
  • IMPORT statement, used in an interface body to enable access to entities of the host scoping unit.
  • MIN() and MAX() for character as well as numeric types.
  • OPEN for “Transparent” or stream I/O.
  • Backwards compatibility with g77’s Application Binary Interface (ABI).
  • Default integers of 32 bits or 64 bits available.
  • Invoke SYSTEM() command.
  • Tabbed source allowed.
  • Symbolic names with $ option.
  • Hollerith data.
  • DOUBLE COMPLEX extension.
  • Varying length for named COMMON.
  • Mix numeric and character in COMMON and EQUIVALENCE.
  • INTEGER kinds: 1, 2, 4, 8.
  • LOGICAL kinds: 1, 2, 4, 8.
  • REAL kinds : 4, 8, (16 is experimental).
  • REAL(KIND=10) for x86-compatible systems. 19 digits of precision, value range 10±4931.
  • List-formatted floating point output prints the minimal number of digits necessary to uniquely distinguish the number.
  • VAX style debug (D) lines.
  • C style string constants option (e.g. ’hello\nworld’).
  • \ and $ edit descriptors.
  • VAX style system intrinsics (SECNDS etc).
  • Unix system extensions library (getenv, etime, stat, etc).
  • Detect non-conformant or non-allocated arrays at run-time.
  • Detection of memory leaks.
  • Traceback of runtime errors.
  • Smart compile feature prevents module compile cascades.
  • F compatibility option. G95 can be built as an F compiler.
  • Program suspend/resume feature.
  • Obsolete real loop index requires compiling with -freal-loops.
  • Quick response by developer on bug reports is typical.
  • Builds with GCC 4.0.3 to 4.1.2 release versions.
  • Supports the CONVERT= specifier in OPEN statements to specify endian conversion. Legal values are ’big endian’, ’little endian’, ’native’ and ’swap’.

Website: www.g95.org
Support: Documentation
Developer: Steven Bosscher, Paul Brook, Arnaud Desitter, Katherine Holcomb, Niels Kristian Bech Jensen, Steven G. Johnson, Tobi Schleuter, Andy Vaught
License: GNU GPL v2

g95 is written in C. Learn C with our recommended free books and free tutorials.

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