| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- Copyright (C) 1999-2014 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being "Funding Free Software", the Front-Cover |
| Texts being (a) (see below), and with the Back-Cover Texts being (b) |
| (see below). A copy of the license is included in the section entitled |
| "GNU Free Documentation License". |
| |
| (a) The FSF's Front-Cover Text is: |
| |
| A GNU Manual |
| |
| (b) The FSF's Back-Cover Text is: |
| |
| You have freedom to copy and modify this GNU Manual, like GNU |
| software. Copies published by the Free Software Foundation raise |
| funds for GNU development. --> |
| <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>The GNU Fortran Compiler: About GNU Fortran</title> |
| |
| <meta name="description" content="The GNU Fortran Compiler: About GNU Fortran"> |
| <meta name="keywords" content="The GNU Fortran Compiler: About GNU Fortran"> |
| <meta name="resource-type" content="document"> |
| <meta name="distribution" content="global"> |
| <meta name="Generator" content="makeinfo"> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <link href="index.html#Top" rel="start" title="Top"> |
| <link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="Introduction.html#Introduction" rel="up" title="Introduction"> |
| <link href="GNU-Fortran-and-GCC.html#GNU-Fortran-and-GCC" rel="next" title="GNU Fortran and GCC"> |
| <link href="Introduction.html#Introduction" rel="prev" title="Introduction"> |
| <style type="text/css"> |
| <!-- |
| a.summary-letter {text-decoration: none} |
| blockquote.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| div.smalllisp {margin-left: 3.2em} |
| kbd {font-style:oblique} |
| pre.display {font-family: inherit} |
| pre.format {font-family: inherit} |
| pre.menu-comment {font-family: serif} |
| pre.menu-preformatted {font-family: serif} |
| pre.smalldisplay {font-family: inherit; font-size: smaller} |
| pre.smallexample {font-size: smaller} |
| pre.smallformat {font-family: inherit; font-size: smaller} |
| pre.smalllisp {font-size: smaller} |
| span.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <a name="About-GNU-Fortran"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="GNU-Fortran-and-GCC.html#GNU-Fortran-and-GCC" accesskey="n" rel="next">GNU Fortran and GCC</a>, Up: <a href="Introduction.html#Introduction" accesskey="u" rel="up">Introduction</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| <hr> |
| <a name="About-GNU-Fortran-1"></a> |
| <h3 class="section">1.1 About GNU Fortran</h3> |
| |
| <p>The GNU Fortran compiler supports the Fortran 77, 90 and 95 standards |
| completely, parts of the Fortran 2003 and Fortran 2008 standards, and |
| several vendor extensions. The development goal is to provide the |
| following features: |
| </p> |
| <ul> |
| <li> Read a user’s program, |
| stored in a file and containing instructions written |
| in Fortran 77, Fortran 90, Fortran 95, Fortran 2003 or Fortran 2008. |
| This file contains <em>source code</em>. |
| |
| </li><li> Translate the user’s program into instructions a computer |
| can carry out more quickly than it takes to translate the |
| instructions in the first |
| place. The result after compilation of a program is |
| <em>machine code</em>, |
| code designed to be efficiently translated and processed |
| by a machine such as your computer. |
| Humans usually are not as good writing machine code |
| as they are at writing Fortran (or C++, Ada, or Java), |
| because it is easy to make tiny mistakes writing machine code. |
| |
| </li><li> Provide the user with information about the reasons why |
| the compiler is unable to create a binary from the source code. |
| Usually this will be the case if the source code is flawed. |
| The Fortran 90 standard requires that the compiler can point out |
| mistakes to the user. |
| An incorrect usage of the language causes an <em>error message</em>. |
| |
| <p>The compiler will also attempt to diagnose cases where the |
| user’s program contains a correct usage of the language, |
| but instructs the computer to do something questionable. |
| This kind of diagnostics message is called a <em>warning message</em>. |
| </p> |
| </li><li> Provide optional information about the translation passes |
| from the source code to machine code. |
| This can help a user of the compiler to find the cause of |
| certain bugs which may not be obvious in the source code, |
| but may be more easily found at a lower level compiler output. |
| It also helps developers to find bugs in the compiler itself. |
| |
| </li><li> Provide information in the generated machine code that can |
| make it easier to find bugs in the program (using a debugging tool, |
| called a <em>debugger</em>, such as the GNU Debugger <code>gdb</code>). |
| |
| </li><li> Locate and gather machine code already generated to |
| perform actions requested by statements in the user’s program. |
| This machine code is organized into <em>modules</em> and is located |
| and <em>linked</em> to the user program. |
| </li></ul> |
| |
| <p>The GNU Fortran compiler consists of several components: |
| </p> |
| <ul> |
| <li> A version of the <code>gcc</code> command |
| (which also might be installed as the system’s <code>cc</code> command) |
| that also understands and accepts Fortran source code. |
| The <code>gcc</code> command is the <em>driver</em> program for |
| all the languages in the GNU Compiler Collection (GCC); |
| With <code>gcc</code>, |
| you can compile the source code of any language for |
| which a front end is available in GCC. |
| |
| </li><li> The <code>gfortran</code> command itself, |
| which also might be installed as the |
| system’s <code>f95</code> command. |
| <code>gfortran</code> is just another driver program, |
| but specifically for the Fortran compiler only. |
| The difference with <code>gcc</code> is that <code>gfortran</code> |
| will automatically link the correct libraries to your program. |
| |
| </li><li> A collection of run-time libraries. |
| These libraries contain the machine code needed to support |
| capabilities of the Fortran language that are not directly |
| provided by the machine code generated by the |
| <code>gfortran</code> compilation phase, |
| such as intrinsic functions and subroutines, |
| and routines for interaction with files and the operating system. |
| |
| </li><li> The Fortran compiler itself, (<code>f951</code>). |
| This is the GNU Fortran parser and code generator, |
| linked to and interfaced with the GCC backend library. |
| <code>f951</code> “translates” the source code to |
| assembler code. You would typically not use this |
| program directly; |
| instead, the <code>gcc</code> or <code>gfortran</code> driver |
| programs will call it for you. |
| </li></ul> |
| |
| |
| |
| <hr> |
| <div class="header"> |
| <p> |
| Next: <a href="GNU-Fortran-and-GCC.html#GNU-Fortran-and-GCC" accesskey="n" rel="next">GNU Fortran and GCC</a>, Up: <a href="Introduction.html#Introduction" accesskey="u" rel="up">Introduction</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| |
| |
| |
| </body> |
| </html> |
