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The Fortran Automatic Coding System for the IBM 704 (October 15, 1956), the first Programmer's Reference Manual for FORTRAN
"In the beginning, there was FORTRAN." (Jim Gray)

FORTRAN[1] is a general-purpose[2], procedural[3], imperative programming language that is especially suited to numeric computation and scientific computing. Originally developed by International Business Machines Corporation (IBM) in the 1950s for scientific and engineering applications, FORTRAN came to dominate this area of programming early on and has been in continuous use in specialized applications such as climate modeling (more) and molecular dynamics modeling (more) for half a century.

FORTRAN 25th anniversary film (IBM), 1982, 12.5 minutes, Windows Media Video (12.8 megabytes).

FORTRAN (an acronym derived from The IBM Mathematical Formula Translating System) encompasses a lineage of versions, each of which evolved to add extensions to the language while retaining compatibility with previous versions. Successive versions have added support for processing of character-based data (FORTRAN 77), array programming (Fortran 90), module-based programming (Fortran 90), object-based programming (Fortran 90), and object-oriented and generic programming (Fortran 2003)

There is now a vast body of Fortran in daily use throughout the scientific and engineering communities. It is the primary language for some of the most intensive supercomputing tasks, such as weather/climate modeling, computational chemistry, quantum chromodynamics (QCD), and simulation of automobile crash dynamics. Indeed, one finds that even today, half a century later, floating-point benchmarks to gauge the performance of new computer processors are still written in Fortran (e.g., CFP2000, the floating-point component of the SPEC CPU2000 benchmarks), an eloquent tribute to the longevity of the language.

History

An IBM 704 mainframe (image courtesy of LLNL)

In late 1953, John W. Backus submitted a proposal to his superiors at IBM to develop a more efficient alternative to assembly language for programming their IBM 704 mainframe computer. A draft specification, "Preliminary Report : Specifications for the IBM Mathematical FORmula TRANslating System, FORTRAN" (PDF). November 10, 1954. {{cite journal}}: Cite journal requires |journal= (help), was prepared. Although originally intended for internal use[4] only on the IBM 704 computer, the language was eventually made available to any customer purchasing an IBM 704. The first "official" manual for FORTRAN appeared in October 1956, with the first FORTRAN compiler delivered in April 1957. This was an optimizing compiler, because customers were reluctant to use a high-level programming language unless its compiler could generate code whose performance was comparable to that of hand-coded assembly language.

The language was widely adopted by scientists for writing numerically intensive programs, which encouraged compiler writers to produce compilers that could generate faster and more efficient code. The inclusion of a complex number data type in the language made Fortran especially suited to technical applications such as electrical engineering.

By 1960, versions of FORTRAN were available for the IBM 709, 650, 1620, and 7090 computers. Significantly, the increasing popularity of FORTRAN spurred competing computer manufacturers to provide FORTRAN compilers for their machines, so that by 1963 over 40 FORTRAN compilers existed. For these reasons, FORTRAN is considered to be the first widely used programming language supported by a number of manufacturers across a variety of computer models [citation needed].

The development of FORTRAN paralleled the early evolution of compiler technology; indeed many advances in the theory and design of compilers were specifically motivated by the need to generate efficient code for FORTRAN programs.

Papers, books, ... (items specific to a Fortran release are listed with that release, below)

  • IEEE (January 1984). "FORTRAN's Twenty-Fifth Anniversary. Special issue". Annals of the History of Computing. 6 (1).
  • Hill, I. D. (1980). Programming Language Standardisation. Ellis Horwood Limited. ISBN 0853121885. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Lohr, Steve (2001). Go To: The Story of the Math Majors, Bridge Players, Engineers, Chess Wizards, Maverick Scientists, & Iconoclasts -- The Programmers Who Created the Software Revolution. Basic Books. For online excerpts, Google "Lohr Fortran Backus Gray".
  • Muxworthy, D.T. (1972). "Standard Fortran - A Short History". The Computer Bulletin. 16.
  • Wexelblat, Richard L. (1981). History of Programming Languages. Academic Press. ISBN 0127450408. Includes Backus' 1978 paper above, together with transcripts of the presentation and Q & A sessions.

FORTRAN initial release

The initial release of FORTRAN for the IBM 704 contained 33 statements. Thirty-two are described in the Programmer's Reference Manual (PDF)., including:

  • DIMENSION and EQUIVALENCE statements
  • Assignment statements
  • Three-way arithmetic IF statement. It is interesting to note that this statement, the primary branching construct, corresponds directly to the branch instruction on the IBM 704, which was a three-way branch.
  • IF statements for checking exceptions (ACCUMULATOR OVERFLOW, QUOTIENT OVERFLOW, and DIVIDE CHECK); and IF statements for manipulating sense switches and sense lights
  • GOTO, computed GOTO, ASSIGN, and assigned GOTO
  • DO loops
  • Formatted I/O: FORMAT, READ, READ INPUT TAPE, WRITE, WRITE OUTPUT TAPE, PRINT, and PUNCH
  • Unformatted I/O: READ TAPE, READ DRUM, WRITE TAPE, and WRITE DRUM
  • Other I/O: END FILE, REWIND, and BACKSPACE
  • PAUSE, STOP, and CONTINUE
  • FREQUENCY statement (for providing optimization hints to the compiler)

The function-statement "was added to the system after the manual was written and before the system was distributed" Backus (1978). "The History of Fortran I, II, and III". {{cite journal}}: Cite journal requires |journal= (help).

IBM Manuals

Papers, books, videos, ...

FOR TRANSIT

The second IBM implementation of FORTRAN, also completed in 1957, was a language translator, translating a subset of IBM 704 FORTRAN to Alan Perlis' IT language.

IBM Manuals

Papers, books, ...

  • Perlis, Alan J. "Internal Translator (IT) A Compiler for the 650". Computation Center, Carnegie Institute of Technology. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help) (document reference is from the IBM FOR TRANSIT manual, above)

FORTRAN II

IBM's FORTRAN II appeared in 1958. The main enhancement was to support procedural programming by allowing user-written subroutines and functions. Six new statements were introduced:

  • SUBROUTINE, FUNCTION, and END
  • CALL and RETURN
  • COMMON

Over the next few years, FORTRAN II would also add support for the DOUBLE PRECISION and COMPLEX data types.

The increasing popularity of FORTRAN led to the publication of the first book written by an independent author[citation needed] about a programming language, Daniel D. McCracken's A Guide to Fortran Programming (Wiley, 1961).

IBM Manuals

Papers, books, ...

  • McCracken, Daniel D. (1961). A Guide to Fortran Programming. Wiley. {{cite book}}: External link in |last= (help)
  • Organick, Elliot (1961). A PRIMER for Programming with the FORTRAN Language.
  • Organick, Elliot (1961). Drill Exercises and Example Problems for A PRIMER for Programming with the FORTRAN Language. Computing and Data Processing Center, University of Houston.

FORTRAN III

IBM also developed a FORTRAN III in 1958 that allowed for inline assembler code among other features; however, this version was never released as a product. Like the 704 FORTRAN and FORTRAN II, FORTRAN III included machine-dependent features that made code written in it unportable from machine to machine. Early versions of FORTRAN provided by other vendors suffered from the same disadvantage.

A pad of Fortran coding forms

Fortran Monitor System

UNDER DEVELOPMENT (well, everything is -- just more so here)

FORTRAN Assembly Program (FAP) was a macro assembler for the IBM 709, 7090, and 7094.

IBM Manuals

Papers, Books, ...

  • Jack Harper's FAP page
  • Weizer, N. A. (Jan. 1981). "History of Operating Systems". Datamation: 119–126. {{cite journal}}: Check date values in: |date= (help)
  • Bashe, C.J. (1986). IBM’s Early Computers. MIT Press. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

FORTRAN IV

Starting in 1961, as a result of customer demands, IBM began development of a FORTRAN IV that removed the machine-dependent features of FORTRAN II (such as READ INPUT TAPE), while adding new features such as a LOGICAL data type, logical Boolean expressions and the logical IF statement as an alternative to the arithmetic IF statement. FORTRAN IV was eventually released in 1962, first for the IBM 7030 ("Stretch") computer, followed by versions for the IBM 7090 and 7094.

IBM Manuals

Textbooks, tutorials

WATFOR, WATFIV, FORGO, PUFFT

See WATFIV programming language. From that page: In the summer of 1965, four undergraduate students of the University of Waterloo, Gus German, Jim Mitchell, Richard Shirley and Robert Zarnke, led by Peter Shantz, developed a FORTRAN compiler for the IBM® 7040 computer and called it WATFOR®. Its objectives were fast compilation speed and effective error diagnostics at both compile and execution time. It eliminated the need for a separate linking procedure and, as a result, FORTRAN programs which contained no syntax errors were placed into immediate execution. Similar experiments were carried on at the University of Wisconsin (FORGO on the IBM 1620) and at Purdue University (PUFFT on the IBM 7090).

Books, tutorials, ...

  • Cress, Paul (April 1970). Fortran IV With Watfor and Watfiv. Prentice-Hall.

FORTRAN 66

Perhaps the most significant development in the early history of FORTRAN was the decision by the American Standards Association (now ANSI) to form a committee to develop an "American Standard Fortran." The resulting two standards, ratified in March 1966, defined two languages, FORTRAN (based on FORTRAN IV, which had served as a de facto standard), and Basic FORTRAN (based on FORTRAN II, but stripped of its machine-dependent features). The FORTRAN defined by the first standard became known as FORTRAN 66 (although many continued to refer to it as FORTRAN IV, the language upon which the standard was largely based). FORTRAN 66 effectively became the first "industry-standard" version of FORTRAN. FORTRAN 66 included:

  • Main program, SUBROUTINE, FUNCTION, and BLOCK DATA program units
  • INTEGER, REAL, DOUBLE PRECISION, COMPLEX, and LOGICAL data types
  • COMMON, DIMENSION, and EQUIVALENCE statements
  • DATA statement for specifying initial values
  • Intrinsic and EXTERNAL (e.g., library) functions
  • Assignment statement
  • GOTO, assigned GOTO, and computed GOTO statements
  • Logical IF and arithmetic (three-way) IF statements
  • DO loops
  • READ, WRITE, BACKSPACE, REWIND, and ENDFILE statements for sequential I/O
  • FORMAT statement
  • CALL, RETURN, PAUSE, and STOP statements
  • Hollerith constants in DATA and FORMAT statements, and as actual arguments to procedures
  • Identifiers of up to six characters in length
  • Comment lines

In 1968 Edsger W. Dijkstra wrote a classic paper on the GOTO statement, "GoTo Considered Harmful". 11 (3). CACM. March 1968. {{cite journal}}: Cite journal requires |journal= (help).

In 1975-1976 Will Crowther and Don Woods using Fortran create the first computer adventure game, Colossal Cave Adventure (also known as ADVENT or Colossal Cave).

Standards

  • ECMA 1965. ECMA Standard on FORTRAN (ECMA-9). European Computer Manufacturers Association.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ASA X3.9-1966. American Standard FORTRAN (PDF). American Standards Association.{{cite book}}: CS1 maint: numeric names: authors list (link) Informally known as FORTRAN 66.
  • ASA X3.10-1966. American Standard Basic FORTRAN. American Standards Association.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ISO 1539-1972. Recommendation: Programming Language FORTRAN. International Organization for Standardization.{{cite book}}: CS1 maint: numeric names: authors list (link)

Textbooks, tutorials

  • Kaufman, Roger Emanuel (1978). A FORTRAN Coloring Book. MIT. ISBN 0262610264. {{cite book}}: External link in |last= (help)CS1 maint: numeric names: authors list (link) "The FORTRAN Coloring Book gave rise to a flood of other books done in the style it created." Kaufman

QUIKTRAN

FORTRAN 77

After the release of the FORTRAN 66 standard, compiler vendors introduced a number of extensions to "Standard Fortran," prompting ANSI in 1969 to begin work on revising the 1966 standard. Final drafts of this revised standard circulated in 1977, leading to formal approval of the new Standard FORTRAN in April 1978. The new standard, known as FORTRAN 77, added a number of significant features to address many of the shortcomings of FORTRAN 66:

  • CHARACTER data type, with vastly expanded facilities for character input and output and processing of character-based data
  • IMPLICIT statement
  • Block IF statement, with optional ELSE and ELSE IF clauses, to provide improved language support for structured programming
  • OPEN, CLOSE, and INQUIRE statements for improved I/O capability
  • Direct-access file I/O
  • PARAMETER statement for specifying constants
  • SAVE statement for persistent local variables
  • Generic names for intrinsic functions

An important practical extension to FORTRAN 77 was the release of MIL-STD-1753 in 1978. This specification, developed by the U. S. Department of Defense, standardized a number of features implemented by most FORTRAN 77 compilers but not included in the ANSI FORTRAN 77 standard. These features would eventually be incorporated into the Fortran 90 standard.

  • DO WHILE and END DO statements
  • INCLUDE statement
  • IMPLICIT NONE variant of the IMPLICIT statement
  • Bit manipulation intrinsics, based on the Industrial Real-Time Fortran (IRTF) Standard

The development of a revised standard to succeed FORTRAN 77 would be repeatedly delayed as the standardization process struggled to keep up with rapid changes in computing and programming practice. In the meantime, as the "Standard FORTRAN" for nearly fifteen years, FORTRAN 77 would become the historically most important dialect.

Standards

Textbooks, tutorials, ...

  • Fortran 77 — FORTRAN 77 documentation
  • Nyhoff, Larry (1995). FORTRAN 77 for Engineers and Scientists with an Introduction to Fortran 90 (4th ed. ed.). Prentice Hall. ISBN 013363003X. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Page, Clive G. (January 1988). The Professional Programmer's Guide to FORTRAN 77 (1st ed. ed.). Hyperion Books. ISBN 0273028561. {{cite book}}: |edition= has extra text (help)CS1 maint: year (link) Out of print and now online.
  • Unit 7.1 FORTRAN 77 — Part of ASPIRE's "Computational Science Textbook" project

Fortran 90

The much delayed (see: Meek, Brian (October 1990). "The Fortran (not the foresight) saga: the light and the dark". Fortran Forum. 9 (2).) successor to FORTRAN 77, informally known as Fortran 90, was finally released as an ANSI Standard in 1992. This major revision added many new features to reflect the significant changes in programming practice that had evolved since the 1978 standard:

  • Free-form source input, also with lowercase Fortran keywords
  • Modules, to group related procedures and data together
  • RECURSIVE procedures
  • A vastly improved argument-passing mechanism, allowing interfaces to be checked at compile time
  • User-written interfaces for generic procedures
  • Operator overloading
  • Derived/abstract data types
  • New data type declaration syntax, to specify the data type and other attributes of variables
  • Ability to operate on arrays as a whole in expressions and assignment statements, thus greatly simplifying math and engineering computations
  • Dynamic memory allocation by means of the ALLOCATABLE attribute and the ALLOCATE and DEALLOCATE statements
  • POINTER attribute, pointer assignment, and NULLIFY statement to facilitate the creation and manipulation of dynamic data structures
  • CASE construct for multi-way selection
  • EXIT and CYCLE statements for "breaking out" of normal DO loop iterations in an orderly way
  • Identifiers up to 31 characters in length
  • Inline comments
  • Portable specification of numerical precision under the user's control

Standards

  • ANSI X3.198-1992 (R1997). American National Standard — Programming Language Fortran Extended. American National Standards Institute.{{cite book}}: CS1 maint: numeric names: authors list (link) Informally known as Fortran 90.
  • ISO/IEC 1539-2-1994. Information Technology - Programming Languages - FORTRAN - Part 2: Varying Length Character Strings.{{cite book}}: CS1 maint: numeric names: authors list (link)

Textbooks, tutorials, ...

  • Ellis, T. M. R. (1994). Fortran 90 Programming (1st ed. ed.). Addison-Wesley. ISBN 0201544466. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • Unit 7.2 Fortran 90 — Part of ASPIRE's "Computational Science Textbook" project

High Performance Fortran (HPF)

About 1993 the High Performance Fortran Forum (HPFF) was organized. HPFF is a coalition of industry, academic and laboratory representatives that works to define the HPF language specification. HPF is a set of extensions to Fortran 90 that provide access to high-performance architecture features while maintaining portability across platforms. HPF uses a SIMD model of computation to support spreading the work of a single array computation over multiple processors. HPFF produced a version 1 document in 1993-94, a version 2 in 1997. Current status ???

Fortran 95

Fortran 95 was a minor revision, mostly to resolve some outstanding issues from the Fortran 90 standard. Nevertheless, Fortran 95 also added a number of extensions, notably from the High Performance Fortran specification:

  • FOR ALL and nested WHERE constructs to aid vectorization
  • User-defined PURE and ELEMENTAL procedures

An important supplement to Fortran 95 was the ISO technical report TR-15581: Enhanced Data Type Facilities, informally known as the Allocatable TR. This specification defined enhanced use of ALLOCATABLE arrays, prior to the availability of fully Fortran 2003-compliant Fortran compilers. Such uses include ALLOCATABLE arrays as derived type components, in procedure dummy argument lists, and as function return values. (ALLOCATABLE arrays are preferable to POINTER-based arrays because ALLOCATABLE arrays are guaranteed by Fortran 95 to be deallocated automatically when they go out of scope, eliminating the possibility of memory leakage. In addition, aliasing is not an issue for optimization of array references, allowing compilers to generate faster code than in the case of pointers.)

Standards

  • ISO/IEC 1539-1-1997 (R2003). Information technology — Programming languages — Fortran — Part 1: Base language.{{cite book}}: CS1 maint: numeric names: authors list (link) Informally known as Fortran 95.
  • ISO/IEC 1539-2:2000. Information technology -- Programming languages -- Fortran -- Part 2: Varying length character strings.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ISO/IEC 1539-3:1999. Information technology - Programming languages - Fortran - Part 3: Conditional compilation.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ISO/IEC TR 15580:2001. Information technology -- Programming languages -- Fortran -- Floating-point exception handling.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ISO/IEC TR 15581:2001. Information technology -- Programming languages -- Fortran -- Enhanced data type facilities.{{cite book}}: CS1 maint: numeric names: authors list (link) Informally known as the Allocatable TR.

Textbooks, tutorials, ...

Fortran 2003

The most recent standard, Fortran 2003, is a major revision introducing a number of extensions:

A comprehensive summary of the new features of Fortran 2003 is available for download as a PDF file or gzipped PostScript file.

Standards

  • ISO/IEC 1539-1:2004. Information technology — Programming languages — Fortran — Part 1: Base language.{{cite book}}: CS1 maint: numeric names: authors list (link) Informally known as Fortran 2003.
  • ISO/IEC 1539-1/Cor1:2006. Information technology - Programming languages - Fortran - Part 1: Base language - Corrigendum.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • ISO/IEC TR 19767:2005. Information technology - Programming languages - Fortran - Enhanced Module Facilities.{{cite book}}: CS1 maint: numeric names: authors list (link)

Textbooks, tutorials

Current Fortran activities

See the ISO Fortran Working Group (WG5) web site for, as described there, "... a summary of the present state of standardization of Fortran and of current developments which will, in due course, lead to further extensions to the language, as well as a brief history of the standardization of the Fortran language and the names of the key individuals and organisations involved:

  • Overview of WG5 and the Standardization Process
  • WG5 Officers and Project Editors
  • WG5 Projects
  • WG5 Electronic Document Archive
  • WG5 Email List
  • Future WG5 Meetings"

Also see: Co-array Fortran.

There is a Fortran newsgroup, comp.lang.fortran on Usenet.

A mailing list for Fortran 90, COMP-FORTRAN-90 Discussion Group and Archives.

The Association for Computing Machinery (ACM) Special Interest Group for Programming Languages (SIGPLAN) publishes the Fortran Forum (subscription required). From their website "SIGPLAN FORTRAN Forum (not included in membership) Addresses the FORTRAN language, its uses, profitability, standardization, further evolution, and the implementation of FORTRAN processors. Published 3 times per year." For a COMPLETE BibTeX bibliography for the journal ACM ForTec Forum (ISSN 0735-3731), and its renamed successor, ACM Fortran Forum (ISSN 1061-7264), for 1982--date, see http://www.math.utah.edu/pub/tex/bib/fortran-forum.bib.

A number of national standards organizations have an active Fortran committee. For some of those committes, neither nationality nor residency are requirements for active, working, participation, but may be required for specific committee votes on national positions.

Variants of Fortran

Specific variants

Vendors of high-performance scientific computers (e.g., Burroughs, CDC, Cray, Honeywell, IBM, Texas Instruments, and UNIVAC) added extensions to Fortran to take advantage of special hardware features such as instruction cache, CPU pipelines, and vector arrays. For example, one of IBM's Fortran compilers (H Extended IUP) had a level of optimization which reordered the machine language instructions to keep multiple internal arithmetic units busy simultaneously. Another example is CFD, a variant of Fortran designed specifically for the ILLIAC IV supercomputer, running at NASA's Ames Research Center.

Object-Oriented Fortran is an object-oriented extension of Fortran, in which data items can be grouped into objects, which can be instantiated and executed in parallel. It was available for Sun, Iris, iPSC, and nCUBE, but is no longer supported.

Such machine-specific extensions have either disappeared over time or have had elements incorporated into the main standards; the major remaining extension is OpenMP, which is a cross-platform extension for shared memory programming. One new extension, CoArray Fortran, is intended to support parallel programming.

Fortran-based languages

Prior to FORTRAN 77, a number of preprocessors were commonly used to provide a friendlier language, while retaining the advantage that the preprocessed code could still be compiled on any machine with a standard FORTRAN compiler. Popular preprocessors included FLECS, MORTRAN, Ratfor, and Ratfiv. (Ratfor and Ratfiv, for example, implemented a remarkably C-like language, outputting preprocessed code in standard FORTRAN 66.[5])

Among the more popular specialized Fortran-based languages that evolved over time are SAS, for generating statistical reports, and SIMSCRIPT, for modeling and simulating large discrete systems.

F was designed to be a clean subset of Fortran 95 that attempted to remove the redundant, unstructured, and deprecated features of Fortran, such as the EQUIVALENCE statement.

Language features

Wikibooks has a book on the topic of: Fortran

The Fortran language features described are not intended to be a comprehensive overview of the Fortran language; that role properly belongs to any of the excellent Fortran textbooks that are available. Rather, they describe some of the more salient features of the language, particularly those peculiar to Fortran. Although both old and new features are described, few of the historic features are used in modern programs. Still, most have been retained in the language to maintain backward compatibility.

Further information: Fortran language features

Code examples

The sample programs can be compiled and run with any standard Fortran compiler (see the end of this article for lists of open-source and proprietary compilers). Most modern Fortran compilers expect a file with a .f extension (for FORTRAN 66 or FORTRAN 77 source, although the FORTRAN 66 dialect may have to be selected specifically with a command-line option) or .f90/.f95 extension (for Fortran 90/95 source, respectively).

Further information: Fortran code examples

Criticisms and rebuttals

Arcane syntax

As what was essentially a first attempt at designing a high-level language, Fortran's syntax is sometimes regarded as archaic by programmers familiar with subsequently developed languages such as C. Fortran has stayed abreast of such advances, however, and contemporary versions have attempted to supersede and deprecate such syntax in favor of more robust and transparent syntax.

Early FORTRAN syntax (prior to Fortran 90) did not in general treat blanks as significant, which made writing robust and efficient lexical analyzers for Fortran very difficult. Subsequent developments such as free-form source have largely resolved these issues.

A language tailored to "specialists"

Historical versions of Fortran could rightly be criticized for arbitrary conventions such as implicit typing and fixed-form source input, which together with a paucity of block structures could allow careless or obfuscated programming practices. However, modern Fortran has overcome such issues. Since its introduction, Fortran has been tuned to scientific and numerical work. Fortran 95 provides concise statements for applying mathematical operations directly to entire arrays, which not only improves program readability but also assists the compiler in vectorizing operations. As another example, from its earliest days Fortran provided full support for complex numbers (used, e.g., in the computation of Fourier transforms and in power engineering calculations), a feature not supported by ANSI C until the advent of the ISO/IEC 9899:1999 ("C99") standard.

For these reasons, while Fortran is seldom used outside of scientific and engineering numerical work, it remains the language of choice for high-performance numerical computing. It is also simple for non-programmers, particularly those with a mathematical or technical background, to learn how to write efficient, numerically robust code in Fortran.

C/C++ is 'just as fast'

Fortran was designed to create fast executable code for scientific programming. One reason for this is that compiled Fortran programs were intended to be comparable in performance to hand-written assembly language from the start. In scientific computing, this means that efficient array processing is of critical concern. Few other languages treat arrays, especially multi-dimensional arrays, as cleanly and simply as Fortran does.

In particular, Fortran data items are not allowed to alias one another, except in very well-defined and explicit situations. This assists Fortran compilers in generating very efficient code, by default, compared to pointer-intensive languages. On the other hand, explicit use of certain C features, such as the register attribute and the C99 restrict attribute can mitigate some of the performance problems of C.

Fortran 95 is slower than FORTRAN 77

Most programs in FORTRAN 77 are valid in Fortran 95, or require only minor changes. The new Fortran features often allow the programmer to express his or her intentions more precisely and explicitly, affording the compiler greater opportunity for optimization. Any observed slowdown resulting from rewriting a FORTRAN 77 program in Fortran 95 is usually caused by improper usage of Fortran 95 features.

Fortran programs require static storage allocation

It is a common misconception that Fortran requires static storage allocation for all local variables. Both the FORTRAN 66 and FORTRAN 77 Standards allowed, but did not require, a fully static implementation. FORTRAN 77 introduced the SAVE statement to allow a programmer to state explicitly which variables are required to retain their values when they go out of scope. Likewise, Fortran 90 introduced RECURSIVE procedures. In a recursive procedure, non-SAVEd local variables must be unique for each active instance of the procedure.


FORTRAN amusements

For a programming language with a half-century legacy, FORTRAN not surprisingly has accumulated its share of jokes and folklore.

  • "GOD is REAL unless declared INTEGER."
  • Joke, circa 1980 (following the standardization of FORTRAN 77): "Q: What will the scientific programming language of the year 2000 look like? ... A: Nobody knows, but its name will be FORTRAN."
  • A good FORTRAN programmer can write FORTRAN code in any language.
  • "The primary purpose of the DATA statement is to give names to constants; instead of referring to pi as 3.141592653589793 at every appearance, the variable PI can be given that value with a DATA statement and used instead of the longer form of the constant. This also simplifies modifying the program, should the value of pi change." —Early FORTRAN manual for Xerox Computers[6]
  • "Consistently separating words by spaces became a general custom about the tenth century A. D., and lasted until about 1957, when FORTRAN abandoned the practice." —Sun FORTRAN Reference Manual
  • "People are very flexible and learn to adjust to strange surroundings — they can become accustomed to read Lisp and Fortran programs, for example." —Art of PROLOG, Leon Sterling and Ehud Shapiro, MIT Press
  • in San Jose, California, there are streets named Fortran Drive and Fortran Court, located near another street, Disk Drive.
  • in the early 1990's a UK pop band, Fortran 5, was formed.

See also Wikiquote/Programming/Programming languages/Fortran.

References

Notes

  1. ^ The names of earlier versions of the language through FORTRAN 77 were conventionally spelled in all-caps (FORTRAN 77 was the last version in which the use of lowercase letters in keywords was strictly nonstandard). The capitalization has been dropped in referring to newer versions beginning with Fortran 90. The official language standards now refer to the language as "Fortran." Because the capitalization (or lack thereof) of the word FORTRAN was never 100% consistent in actual usage, and because many hold impassioned beliefs on the issue, this article, rather than attempt to be normative, adopts the convention of using the all-caps FORTRAN in referring to versions of FORTRAN through FORTRAN 77 and the title-caps Fortran in referring to versions of Fortran from Fortran 90 onward. This convention is reflected in the capitalization of FORTRAN in the ANSI X3.9-1966 (FORTRAN 66) and ANSI X3.9-1978 (FORTRAN 77) standards and the title caps Fortran in the ANSI X3.198-1992 (Fortran 90) standard.
  2. ^ Since FORTRAN 77, which introduced the CHARACTER data type.
  3. ^ Since FORTRAN II (1958).
  4. ^ "The [FORTRAN] project was initially intended purely for use by IBM on a single computer." Ellis, T. M. R. (1982). A Structured Approach to FORTRAN 77 Programming. Addison-Wesley. Page 8.
  5. ^ This is not altogether surprising, as Brian Kernighan, one of the co-creators of Ratfor, is also co-author of The C Programming Language.
  6. ^ Prior to FORTRAN 77, which introduced the PARAMETER statement (the preferred method of defining constants), the DATA statement was the conventional way to define constants, although this statement merely specified initial values and did not prevent the corresponding variables from being modified (as by regular assignment statements).

History

Tutorials

References

Wikibooks has a book on the topic of: Fortran

Code repositories

Free (open-source) compilers

  • g77: "g77 is a free Fortran 77 compiler...now integrated into the GNU Compiler Collection (GCC)." Note: GCC, as of version 4.0, now includes GFortran as the default Fortran compiler in lieu of g77.
  • g95: "The goal of the g95 project is to create a free, open source Fortran 95 compiler and runtime libraries." Note: Once an open, collaborative effort, the project has now reverted to the exclusive control of the original g95 project creator.
  • GFortran: "The GNU Fortran 95 compiler, part of GCC." Distributed as part of GCC as of GCC 4.0, GFortran is likely to become the de facto "standard" Fortran compiler (much as g77 was through GCC 3.4.6).
  • High Performance Computing for Mac OS X — Fortran compilers for Mac OS X.
  • Open Watcom: "A joint effort between SciTech Software Inc, Sybase and the Open Source development community to maintain and enhance the Watcom C/C++ and Fortran cross compilers and tools."

Proprietary compilers

Free graphical libraries/GUI

Proprietary/non-free graphical libraries/GUI

  • DISLIN: "DISLIN is a high-level plotting library for displaying data as curves, polar plots, bar graphs, pie charts, 3D-color plots, surfaces, contours and maps." For DOS, Linux, Mac OS X, OpenVMS, UNIX, Windows. "Free for non-commercial use" (but not free).
  • SansGUI: Requires Microsoft Visual C/C++ 6.0+ or Compaq Visual Fortran 6.1+. For Windows.
  • Winteracter: "The Fortran 9x GUI Toolset." For Linux, Mac OS X, Windows.
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