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Fortran
The Fortran Automatic Coding System for the IBM 704 (October 15, 1956), the first Programmer's Reference Manual for Fortran
The Fortran Automatic Coding System for the IBM 704 (October 15, 1956), the first Programmer's Reference Manual for Fortran
Paradigm multi-paradigm: procedural, imperative, structured, object-oriented
Appeared in 1957
Designed by John Backus
Developer John Backus & IBM
Typing discipline strong, static
Major implementations Absoft, GFortran, G95, Intel, Lahey/Fujitsu, Open Watcom, Pathscale, PGI, Silverfrost, Sun, XL Fortran, others
Influenced ALGOL 58, PL/I

Fortran (previously FORTRAN[1]) is a general-purpose,[2] procedural,[3] imperative programming language that is especially suited to numeric computation and scientific computing. The IBM 704, the first mass-produced Computer with Floating point arithmetic hardware was introduced by IBM in April 1954. A programming paradigm is a fundamental style of Computer programming. A multi-paradigm programming language is a Programming language that supports more than one Programming paradigm. Procedural programming can sometimes be used as a synonym for Imperative programming (specifying the steps the program must take to reach the desired state but can also In Computer science, imperative programming is a Programming paradigm that describes computation in terms of statements that change a program state Structured programming can be seen as a subset or subdiscipline of Procedural programming, one of the major Programming paradigms It is most famous for removing or Object-oriented programming (OOP is a Programming paradigm that uses " objects " and their interactions to design applications and computer programs Year 1957 ( MCMLVII) was a Common year starting on Tuesday (link displays the 1957 Gregorian calendar) John Warner Backus ( December 3, 1924 – March 17, 2007) was an American Computer scientist. A software developer is a person or organization concerned with facets of the software development process wider than design and coding a somewhat broader scope of John Warner Backus ( December 3, 1924 – March 17, 2007) was an American Computer scientist. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology In Computer science, a type system defines how a Programming language classifies values and expressions into '''types''', how it can In Computer science and Computer programming, the term strong typing is used to describe those situations where Programming languages specify one or more In Computer science, a type system defines how a Programming language classifies values and expressions into '''types''', how it can Implementation is the realization of an application or execution of a Plan, idea Model, Design, Specification, standard, Algorithm gfortran is the name of the GNU Fortran Compiler, which is part of the GNU Compiler Collection (GCC G95 is a free, portable, Open source Fortran 95 Compiler, with some Fortran 2003 extensions primarily developed by Andy Intel Fortran Compiler - Fortran Compiler developed by Intel. ALGOL 58, originally known as IAL, is one of the family of ALGOL computer Programming languages It was an early compromise design soon superseded by PL/I ("Programming Language One" ˌpiːˌɛlˈwʌn is an imperative computer Programming language designed for scientific engineering The term domain-specific language ( DSL) has become popular in recent years in Software development to indicate a Programming language or Specification Procedural programming can sometimes be used as a synonym for Imperative programming (specifying the steps the program must take to reach the desired state but can also In Computer science, imperative programming is a Programming paradigm that describes computation in terms of statements that change a program state A programming language is an Artificial language that can be used to write programs which control the behavior of a machine particularly a Computer. Numerical analysis is the study of Algorithms for the problems of continuous mathematics (as distinguished from Discrete mathematics) Computational science (or scientific computing) is the field of study concerned with constructing Mathematical models and numerical solution techniques and using computers Originally developed by IBM in the 1950s for scientific and engineering applications, Fortran came to dominate this area of programming early on and has been in continual use for over half a century in computationally intensive areas such as numerical weather prediction, finite element analysis, computational fluid dynamics (CFD), computational physics, and computational chemistry. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology The 1950s Decade refers to the years of 1950 to 1959 inclusive Numerical weather prediction uses current weather conditions as input into Mathematical models of the atmosphere to predict the weather. Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve Computational physics is the study and implementation of numerical Algorithms in order to solve problems in Physics for which a quantitative theory already exists Computational chemistry is a branch of Chemistry that uses computers to assist in solving chemical problems It is one of the most popular languages in the area of High-performance computing and programs to benchmark and rank the worlds fastest supercomputers are written in Fortran[4]. High-performance computing (HPC uses Supercomputers and Computer clusters to solve advanced computing problems The TOP500 project ranks and details the 500 most powerful known Computer systems in the world

Fortran (a blend word derived from The IBM Mathematical Formula Translating System) encompasses a lineage of versions, each of which evolved to add extensions to the language while usually retaining compatibility with previous versions. In Linguistics, a blend is a word formed from parts of two other words Successive versions have added support for processing of character-based data (FORTRAN 77), array programming, module-based programming and object-based programming (Fortran 90 / 95), and object-oriented and generic programming (Fortran 2003). Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to In Computer science, array programming languages (also known as vector or multidimensional languages generalize operations on scalars to apply Modular programming is a software design technique that increases the extent to which software is composed from separate parts called modules Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to Object-oriented programming (OOP is a Programming paradigm that uses " objects " and their interactions to design applications and computer programs Generic programming is a style of Computer programming in which algorithms are written in terms of to-be-specified-later types that are then instantiated

Contents

History

An IBM 704 mainframe (image courtesy of LLNL)
An IBM 704 mainframe (image courtesy of LLNL)
FORTRAN code on a punch card, showing the specialized uses of columns 1-5, 6 and 73-80.
FORTRAN code on a punch card, showing the specialized uses of columns 1-5, 6 and 73-80. The IBM 704, the first mass-produced Computer with Floating point arithmetic hardware was introduced by IBM in April 1954. Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data The Lawrence Livermore National Laboratory ( LLNL) in Livermore California is a scientific research laboratory founded by the University of California in 1952

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. John Warner Backus ( December 3, 1924 – March 17, 2007) was an American Computer scientist. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology The IBM 704, the first mass-produced Computer with Floating point arithmetic hardware was introduced by IBM in April 1954. Backus' historic FORTRAN team consisted of programmers Richard Goldberg, Sheldon F. Best, Harlan Herrick, Peter Sheridan, Roy Nutt, Robert Nelson, Irving Ziller, Lois Haibt and David Sayre. Lois Haibt is perhaps most famous for being a member of the ten person team that invented FORTRAN, the first successful high level Programming language.

A draft specification for The IBM Mathematical Formula Translating System was completed by mid-1954. The first manual for FORTRAN appeared in October 1956, with the first FORTRAN compiler delivered in April 1957. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another 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. Compiler optimization is the process of tuning the output of a Compiler to minimize or maximize some attribute of an Executable computer program In computing a high-level programming language is a Programming language with strong abstraction from the details of the computer See the terminology section below for information regarding inconsistent use of the terms assembly and assembler

While the community was skeptical that this new method could possibly out-perform hand-coding, it reduced the amount of programming statements necessary to operate a machine by a factor of 20, and quickly gained acceptance. Said creator John Backus during a 1979 interview with Think, the IBM employee magazine, "Much of my work has come from being lazy. I didn't like writing programs, and so, when I was working on the IBM 701 (an early computer), writing programs for computing missile trajectories, I started work on a programming system to make it easier to write programs. The IBM 701, known as the Defense Calculator while in development was announced to the public on April 29, "[5]

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. Complex plane In Mathematics, the complex numbers are an extension of the Real numbers obtained by adjoining an Imaginary unit, denoted A data type in Programming languages is an attribute of a datum which tells the computer (and the programmer something about the kind of datum it is

By 1960, versions of FORTRAN were available for the IBM 709, 650, 1620, and 7090 computers. The IBM 709 was an early Computer system introduced by IBM in August 1958. The IBM 650 ( photo was one of IBM ’s early Computers and the world’s first mass-produced ( photo computer The IBM 1620 was announced by IBM on October 21, 1959 and marketed as an inexpensive "scientific computer" The IBM 7090 was a second-generation Transistorized version of the earlier IBM 709 vacuum tube Mainframe computers and was designed for "large-scale 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 across a variety of computer architectures.

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. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another

FORTRAN

The initial release of FORTRAN for the IBM 704 contained 32 statements, including:

FORTRAN II

IBM's FORTRAN II appeared in 1958. A front panel was used on early electronic computers to display and allow the alteration of the state of the machine's internal registers and memory. In Computing, optimization is the process of modifying a system to make some aspect of it work more efficiently or use fewer resources The main enhancement was to support procedural programming by allowing user-written subroutines and functions. Procedural programming can sometimes be used as a synonym for Imperative programming (specifying the steps the program must take to reach the desired state but can also Six new statements were introduced:

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

Simple Fortran II program

This program, for Heron's formula, has one data card input, with simple zero-data edit check. In Geometry, Heron's (or Hero's formula states that the Area (A of a Triangle whose sides have lengths a, b, and If one of the input values is zero or negative, then the program will end with an error code of "STOP 1" in the job control card listing following the execution of the program. Normal output will be one line printed with A, B, C, and AREA on the "report" page following the compilation with no specific units are stated; and with a normal "STOP" in the job card listing. 

C AREA OF A TRIANGLE WITH A STANDARD SQUARE ROOT FUNCTION 
C INPUT - CARD READER UNIT 5, INTEGER INPUT
C OUTPUT - LINE PRINTER UNIT 6, REAL OUTPUT
C INPUT ERROR DISPLAY ERROR OUTPUT CODE 1 IN JOB CONTROL LISTING
      READ INPUT TAPE 5, 501, IA, IB, IC
  501 FORMAT (3I5)
C IA, IB, AND IC MAY NOT BE NEGATIVE
C FURTHERMORE, THE SUM OF TWO SIDES OF A TRIANGLE
C IS GREATER THAN THE THIRD SIDE, SO WE CHECK FOR THAT, TOO
      IF (IA) 777, 777, 701
  701 IF (IB) 777, 777, 702
  702 IF (IC) 777, 777, 703
  703 IF (IA+IB-IC) 777,777,704
  704 IF (IA+IC-IB) 777,777,705
  705 IF (IB+IC-IA) 777,777,799
  777 STOP 1
C USING HERON'S FORMULA WE CALCULATE THE
C AREA OF THE TRIANGLE
  799 S = FLOATF (IA + IB + IC) / 2. 0
      AREA = SQRT( S * (S - FLOATF(IA)) * (S - FLOATF(IB)) *
     +     (S - FLOATF(IC)))
      WRITE OUTPUT TAPE 6, 601, IA, IB, IC, AREA
  601 FORMAT (4H A= ,I5,5H  B= ,I5,5H  C= ,I5,8H  AREA= ,F10. 2, 
     +        13H SQUARE UNITS)
      STOP
      END

FORTRAN III

A FORTRAN coding form, formerly printed on paper and intended to be used by programmers to prepare programs for punching onto cards by card punch operators. Now obsolete.
A FORTRAN coding form, formerly printed on paper and intended to be used by programmers to prepare programs for punching onto cards by card punch operators. A key punch is a device for entering data into Punched cards by precisely punching holes at locations designated by the keys struck by the operator Now obsolete.

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.

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. Year 1961 ( MCMLXI) was a Common year starting on Sunday (link will display full calendar of the Gregorian calendar. A Boolean expression is an Expression that results in a Boolean value, that is TRUE or FALSE FORTRAN IV was eventually released in 1962, first for the IBM 7030 ("Stretch") computer, followed by versions for the IBM 7090 and IBM 7094. The IBM 7030, also known as Stretch, was IBM 's first Transistorized Supercomputer. The IBM 7090 was a second-generation Transistorized version of the earlier IBM 709 vacuum tube Mainframe computers and was designed for "large-scale The IBM 7090 was a second-generation Transistorized version of the earlier IBM 709 vacuum tube Mainframe computers and was designed for "large-scale

By 1965, Fortran IV was supposed to be the "standard" and in compliance with American Standards Association X3. Year 1965 ( MCMLXV) was a Common year starting on Friday (link will display full calendar of the 1965 Gregorian calendar. 4. 3 FORTRAN Working Group. [8]

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, approved 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:

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. Hollerith constants, named in honor of Herman Hollerith, were used in early FORTRAN programs to allow manipulation of character data Final drafts of this revised standard circulated in 1977, leading to formal approval of the new FORTRAN standard 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:

(ASCII functions were demanded by the U. S. Department of Defense, in their conditional approval vote. The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government )

In this revision of the standard, a number of features were removed or altered in a manner that might invalidate previously standard-conforming programs. (Removal was the only allowable alternative to X3J3 at that time, since the concept of "deprecation" was not yet available for ANSI standards. ) While most of the 24 items in the conflict list (see Appendix A2 of X3. 9-1978) addressed loopholes or pathological cases permitted by the previous standard but rarely used, a small number of specific capabilities were deliberately removed, such as:

GREET = 12HHELLO THERE!
DIMENSION A(10,5)
Y= A(11,1)

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. The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government These features would eventually be incorporated into the Fortran 90 standard.

The IEEE 1003. Bit manipulation is the act of algorithmically manipulating Bits or other pieces of data shorter than a Byte. Industrial Real-Time Fortran ( IRTF) was developed during the decade of 1970-1980 to augment the Fortran language with library bindings useful for process and device The Institute of Electrical and Electronics Engineers or IEEE (read eye-triple-e) is an international Non-profit, professional organization 9 POSIX Standard, released in 1991, provided a simple means for Fortran-77 programmers to issue POSIX system calls. POSIX (ˈpɒzɪks or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define Over 100 calls were defined in the document — allowing access to POSIX-compatible process control, signal handling, file system control, device control, procedure pointing, and stream I/O in a portable manner.

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.

Control Data Corporation computers had another version of FORTRAN 77, called Minnesota FORTRAN, with variations in output constructs, special uses of COMMONs and DATA statements, optimizations code levels for compiling, and detailed error listings, extensive warning messages, and debugs. Control Data Corporation (CDC, was one of the pioneering Supercomputer firms [9]

Fortran 90

The much delayed successor to FORTRAN 77, informally known as Fortran 90, was finally released as an ISO standard in 1991 and 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:

Obsolescence & deletions

Unlike the previous revision, Fortran 90 did not delete any features. (Appendix B. 1 says, "The list of deleted features in this standard is empty. ") Any standard-conforming FORTRAN 77 program is also standard-conforming under Fortran 90, and either standard should be usable to define its behavior.

A small set of features were identified as "obsolescent" and expected to be removed in a future standard.

Obsolescent feature Example Status / 95
Arithmetic IF-statement     IF (X) 10, 20, 30
Non-integer DO parameters or control variables     DO 9 X= 1. 7, 1. 6, -0. 1 Deleted
Shared DO-loop termination or
termination with a statement
other than END DO or CONTINUE  		     DO 9 J= 1, 10

        DO 9 K= 1, 10
9   L= J + K
Branching to END IF

from outside a block

 66  GO TO 77 ; . . .

    IF (E) THEN ;     . . .
77  END IF

 Deleted
Alternate return     CALL SUBR( X, Y *100, *200 )
PAUSE statement     PAUSE 600 Deleted
ASSIGN statement
  and assigned GO TO statement		 100  . . .

    ASSIGN 100 TO H
    . . .
    GO TO H . . .

Deleted
Assigned FORMAT specifiers     ASSIGN F TO 606 Deleted
H edit descriptors 606 FORMAT ( 9H1GOODBYE. ) Deleted
Computed GO TO statement     GO TO (10, 20, 30, 40), index (Obso. )
Statement functions     FOIL( X, Y )= X**2 + 2*X*Y + Y**2 (Obso. )
DATA statements
  among executable statements		     X= 27. 3

    DATA A, B, C / 5. 0, 12. 0. 13. 0 /     . . .

(Obso. )
CHARACTER* form of CHARACTER declaration     CHARACTER*8 STRING   ! Use CHARACTER(8) (Obso. )
Assumed character length functions
Fixed form source code * Column 1 contains * or ! or C for comments.
C       Column 6 for continuation.

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:

Several features noted in Fortran 90 to be deprecated were removed from Fortran 95:

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 Computer science, a memory leak is a particular type of unintentional memory consumption by a Computer program where the program fails to release memory In addition, aliasing is not an issue for optimization of array references, allowing compilers to generate faster code than in the case of pointers. In Computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program )

Another important supplement to Fortran 95 was the ISO technical report TR-15580: Floating-point exception handling, informally known as the IEEE TR. This specification defined support for IEEE floating-point arithmetic and floating point exception handling. The IEEE Standard for Binary Floating-Point Arithmetic ( IEEE 754) is the most widely-used standard for floating-point computation and is followed by many In Computing, floating point describes a system for numerical representation in which a string of digits (or Bits represents a Real number. Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of a condition that changes the normal flow of execution

Conditional compilation and varying length strings

In addition to the mandatory "Base language" (defined in ISO/IEC 1539-1 : 1997), the Fortran 95 language also includes two optional modules:

which, together, comprise the multi-part International Standard (ISO/IEC 1539).

According to the standards developers, "the optional parts describe self-contained features which have been requested by a substantial body of users and/or implementors, but which are not deemed to be of sufficient generality for them to be required in all standard-conforming Fortran compilers. " Nevertheless, if a standard-conforming Fortran does provide such options, then they "must be provided in accordance with the description of those facilities in the appropriate Part of the Standard. "

Fortran 2003

The most recent standard, Fortran 2003, is a major revision introducing many new features. A comprehensive summary of the new features of Fortran 2003 is available at the Fortran Working Group (WG5) official Web site. [10]

From that article, the major enhancements for this revision include:

An important supplement to Fortran 2003 was the ISO technical report TR-19767: Enhanced module facilities in Fortran. This report provided submodules, which make Fortran modules more similar to Modula-2 modules. Modula-2 is a computer Programming language invented by Niklaus Wirth at ETH, around 1978 as a successor to his intermediate language Modula They are similar to Ada private child subunits. This allows the specification and implementation of a module to be expressed in separate program units, which improves packaging of large libraries, allows preservation of trade secrets while publishing definitive interfaces, and prevents compilation cascades.

Fortran 2008

Efforts are underway to develop a revision to Fortran 2003, tentatively called Fortran 2008. As with Fortran 95, this is intended to be a minor upgrade, incorporating clarifications and corrections to Fortran 2003, as well as introducing a select few new capabilities. As of February 2007, the proposed new capabilities include[11]

In August 2007, the BIT data type was removed. Co-array Fortran, formerly known as F--, is an extension of Fortran 95/2003 for Parallel processing created by Robert Numrich and John Reid A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication In February 2008, Coarrays were scaled back: Parallel I/O and teams were removed.

The complete original work plan is available at http://j3-fortran.org/doc/year/07/07-010.html.

The legacy of FORTRAN

Since Fortran has been in use for more than fifty years, there is 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 and climate modeling, computational fluid dynamics, computational chemistry, and computational physics. Numerical weather prediction uses current weather conditions as input into Mathematical models of the atmosphere to predict the weather. This article is about the theories and mathematics of climate modeling Computational fluid dynamics (CFD is one of the branches of Fluid mechanics that uses Numerical methods and algorithms to solve and analyze problems that involve Computational chemistry is a branch of Chemistry that uses computers to assist in solving chemical problems Computational physics is the study and implementation of numerical Algorithms in order to solve problems in Physics for which a quantitative theory already exists Even today, half a century later, a lot of the 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). The Standard Performance Evaluation Corporation (SPEC is a Non-profit organization that aims to produce "fair impartial and meaningful benchmarks for computers

Language features

The Fortran language features described are intended to be a fairly comprehensive overview of the Fortran language; full details may be found in any of several Fortran textbooks. Only those features widely used in new programs are described, as few of the historic features are used in modern programs. Still, most have been retained in the language to maintain backward compatibility. In Technology, especially Computing (irrespective of platform a product is said to be backward compatible when it is able to take the place of an older product

For more details on this topic, see Fortran language features. See also Fortran#Language features This is a comprehensive overview of features of the Fortran 95 language, the version supported by almost all existing

Portability

Portability was a problem in the early days because there was no agreed standard—not even IBM's reference manual—and computer companies vied to differentiate their offerings from others by providing incompatible features. Standards have improved portability. The 1966 standard provided a reference syntax and semantics, but vendors continued to provide incompatible extensions. Although careful programmers were coming to realize that use of incompatible extensions caused expensive portability problems, and were therefore using programs such as The PFORT Verifier, it was not until after the 1977 standard, when the National Bureau of Standards (now NIST) published FIPS PUB 69, that processors purchased by the U. S. Government were required to diagnose extensions of the standard. Rather than offer two processors, essentially every compiler eventually had at least an option to diagnose extensions.

Incompatible extensions were not the only portability problem. For numerical calculations, it is important to take account of the characteristics of the arithmetic. This was addressed by Fox et al. in the context of the 1966 standard by the PORT library. The ideas therein became widely used, and were eventually incorporated into the 1990 standard by way of intrinsic inquiry functions. The widespread (now almost universal) adoption of the IEEE 754 standard for binary floating-point arithmetic has essentially removed this problem. The IEEE Standard for Binary Floating-Point Arithmetic ( IEEE 754) is the most widely-used standard for floating-point computation and is followed by many

Access to the computing environment (e. g. the program's command line, environment variables, textual explanation of error conditions) remained a problem until it was addressed by the 2003 standard.

Large collections of "library" software that could be described as being loosely-related to engineering and scientific calculations, such as graphics libraries, have been written in C, and therefore access to them presented a portability problem. This has been addressed by incorporation of C interoperability into the 2003 standard.

It is now possible (and relatively easy) to write an entirely portable program in Fortran, even without recourse to a preprocessor.

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. The Burroughs Corporation began in 1886 as the American Arithmometer Company in St Control Data Corporation (CDC, was one of the pioneering Supercomputer firms Cray Inc ( is a Supercomputer manufacturer based in Seattle Washington. Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology Texas Instruments ( better known in the electronics industry (and popularly as TI, is an American company based in Dallas, Texas, USA UNIVAC serves as the catch-all name for the American manufacturers of the lines of mainframe computers by that name which through mergers and acquisitions underwent In Computer science, a cache (kæʃ like "cash") is a collection of data duplicating original In Computing, a pipeline is a set of data processing elements connected in series so that the output of one element is the input of the next one 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. Machine code or machine language is a system of instructions and data executed directly by a Computer 's Central processing unit. In Computer science, an instruction is a single operation of a processor defined by an Instruction set architecture. Another example is CFD, a special variant of Fortran designed specifically for the ILLIAC IV supercomputer, running at NASA's Ames Research Center. ILLIAC IV was one of the most infamous Supercomputers ever in a series of research machines ILLIACs, from the University of Illinois. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program NASA Ames Research Center (ARC is a NASA facility located at Moffett Federal Airfield, which covers 43 acres at the borders of the cities of Mountain View IBM Research Labs also developed an extended FORTRAN-based language called "VECTRAN" for processing of vectors and matricies.

Object-Oriented Fortran was an object-oriented extension of Fortran, in which data items can be grouped into objects, which can be instantiated and executed in parallel. 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. The OpenMP (Open Multi-Processing is an Application programming interface (API that supports multi-platform Shared memory Multiprocessing programming One new extension, CoArray Fortran, is intended to support parallel programming. Co-array Fortran, formerly known as F--, is an extension of Fortran 95/2003 for Parallel processing created by Robert Numrich and John Reid

FOR TRANSIT for the IBM 650

"FOR TRANSIT" was the name of a reduced version of the IBM 704 FORTRAN language, which was implemented for the IBM 650, using a translator program developed at Carnegie [12] in the late 1950s. The following comment appears in the IBM Reference Manual ("FOR TRANSIT Automatic Coding System" C28-4038, Copyright 1957, 1959 by IBM):

The FORTRAN system was designed for a more complex machine than the 650, and consequently some of the 32 statements found in the FORTRAN Programmer's Reference Manual are not acceptable to the FOR TRANSIT system. In addition, certain restrictions to the FORTRAN language have been added. However, none of these restrictions make a source program written for FOR TRANSIT incompatible with the FORTRAN system for the 704.

The permissible statements were:

Arithmetic assignment statements, e. g. a = b
GO to n
GO TO (n1, n2, . . . , nm), i
IF (a) n1, n2, n3
PAUSE
STOP
DO n i = m1, m2
CONTINUE
END
READ n, list
PUNCH n, list
DIMENSION V, V, V, . . .
EQUIVALENCE (a,b,c), (d,c), . . .

Up to ten subroutines could be used in one program.

FOR TRANSIT statements were limited to columns 7 thru 56, only. Punched cards were used for input and output on the IBM 650. Three passes were required to translate source code to the "IT" language, then to compile the IT statements into SOAP assembly language, and finally to produce the object program, which could then be loaded into the machine to run the program (using punched cards for data input, and outputting results onto punched cards. )

Two versions existed for the 650s with a 2000 word memory drum: FOR TRANSIT I (S) and FOR TRANSIT II, the latter for machines equipped with indexing registers and automatic floating point decimal (bi-quinary) arithmetic. Appendix A of the manual included wiring diagrams for the IBM 533 control panel.

Fortran-based languages

Prior to FORTRAN 77, a number of preprocessors were commonly used to provide a friendlier language, with the advantage that the preprocessed code could be compiled on any machine with a standard FORTRAN compiler. In Computer science, a preprocessor is a program that processes its input data to produce output that is used as input to another program Popular preprocessors included FLECS, MORTRAN, Ratfor, and Ratfiv. Mortran ( M ore F' ortran') is an extension of the Fortran Programming language used for scientific computation Ratfor (short for RAT ional FOR tran is a Programming language implemented as a Preprocessor for Fortran 66 Ratfiv is an enhanced version of the Ratfor programming language, a Preprocessor for Fortran designed to give it C -like capabilities (Ratfor and Ratfiv, for example, implemented a remarkably C-like language, outputting preprocessed code in standard FORTRAN 66. tags please moot on the talk page first! --> In Computing, C is a general-purpose cross-platform block structured [13])

The Fortran-95 Standard includes an optional Part 3 which defines an optional conditional compilation capability. The C preprocessor ( cpp) is the Preprocessor for the C programming language. This capability is often referred to as "CoCo".

Many Fortran compilers have integrated subsets of the C preprocessor into their systems. The C preprocessor ( cpp) is the Preprocessor for the C programming language.

SIMSCRIPT is an application specific Fortran preprocessor for modeling and simulating large discrete systems. SIMSCRIPT is a free-form English -like general-purpose Simulation language conceived by Harry Markowitz and Bernard Hausner at the RAND Corporation

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. F is a compiled, structured, array programming language especially well suited to education and scientific computing

Code examples

The sample programs can be compiled and run with any standard Fortran compiler (see the end of this article for lists of compilers). Most modern Fortran compilers expect a file with a . f or . for extension (for FORTRAN 66 or FORTRAN 77 fixed-form 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 free-form source, respectively).

For more details on this topic, see Wikibooks:Fortran/Fortran examples.

FORTRAN quotations

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

From the historical record

References in popular culture

Letter O considered harmful

During the same Fortran Standards Committee meeting at which the name "FORTRAN 77" was chosen, a technical proposal was somehow smuggled into the official distribution, bearing the title, "Letter O considered harmful". This deceptively simple proposal purported to address the confusion that sometimes arises between the letter "O" and the numeral zero, by eliminating the letter from allowable variable names. However, the method proposed was to eliminate the letter from the character set entirely (thereby retaining 48 as the number of lexical characters, which the colon had increased to 49).

Among the "PRO" arguments was the assertion that this would also promote structured programming, by making it impossible to use the notorious GO TO statement as before. (Troublesome FORMAT statements would be eliminated, as well. )

The sole "CON" argument conceded that "this might invalidate some existing programs" but noted that most of these "probably were non-conforming, anyway". [18]

References

Textbooks

"Core" language standards

Related standards

Notes

  1. ^ The names of earlier versions of the language through FORTRAN 77 were conventionally spelled in all-caps (FORTRAN 77 was the 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. International standards are Standards developed by international Standards organisations International standards are available for consideration and use worldwide " 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. ^ http://en.wikipedia.org/wiki/LINPACK and http://www.top500.org/project/linpack
  5. ^ Fortran creator John Backus dies - Gadgets - MSNBC.com
  6. ^ Note: It is commonly believed that this statement corresponded to a three-way branch instruction on the IBM 704. This is not true, the 704 branch instructions all contained only one destination address (e. g. , TZE — Transfer AC Zero, TNZ — Transfer AC Not Zero, TPL — Transfer AC Plus, TMI — Transfer AC Minus). The machine (and its successors in the 700/7000 series) did have a three-way skip instruction (CAS — Compare AC with Storage), which was probably the origin of this belief, but using this instruction to implement the IF would consume 4 instruction words, require the constant Zero in a word of storage, and take 3 machine cycles to execute; using the Transfer instructions to implement the IF could be done in 1 to 3 instruction words, required no constants in storage, and take 1 to 3 machine cycles to execute. The IBM 700/7000 series was a series of large scale ( mainframe) Computer systems made by IBM through An optimizing compiler like FORTRAN would most likely select the more compact and usually faster Transfers instead of the Compare (use of Transfers also allowed the FREQUENCY statement to optimize IFs, which could not be done using the Compare). Also the Compare considered -0 and +0 to be different values while the Transfer Zero and Transfer Not Zero considered them to be the same.
  7. ^ The FREQUENCY statement in FORTRAN was used originally and optionally to give branch probabilities for the three branch cases of the Arithmetic IF statement to bias the way code was generated and order of the basic blocks of code generated, in the global optimisation sense, were arranged in memory for optimality. The first FORTRAN compiler used this weighting to do a Monte Carlo simulation of the run-time generated code at compile time. Monte Carlo methods are a class of Computational Algorithms that rely on repeated Random sampling to compute their results It was very sophisticated for its time. This technique is documented in the original article in 1957 on the first FORTRAN compiler implementation by J. Backus, et al. Many years later, the FREQUENCY statement had no effect on the code, and was treated as a comment statement, since the compilers no longer did this kind of compile-time simulation. Below is a part of the 1957 paper, "The FORTRAN Automatic Coding System" by Backus, et al. , with this snippet on the FREQUENCY statement and its use in a compile-time Monte Carlo simulation of the run-time to optimise the code generated. Monte Carlo methods are a class of Computational Algorithms that rely on repeated Random sampling to compute their results Quoting …

    The fundamental unit of program is the basic block; a basic block is a stretch of program which has a single entry point and a single exit point. In Computing, a basic block is code that has one entry point (i The purpose of section 4 is to prepare for section 5 a table of predecessors (PRED table) which enumerates the basic blocks and lists for every basic block each of the basic blocks which can be its immediate predecessor in flow, together with the absolute frequency of each such basic block link. This table is obtained by an actual "execution" of the program in Monte-Carlo fashion, in which the outcome of conditional transfers arising out of IF-type statements and computed GO TO'S is determined by a random number generator suitably weighted according to whatever FREQUENCY statements have been provided.

  8. ^ McCraken, Daniel D. (1965(3rd printing 1968)). A Guide to FORTRAN IV Programming. John Wiley & Sons, Inc. , New York. LCCCN 65-26848.   Preface p. v
  9. ^ Chilton Computing with FORTRAN
  10. ^ Fortran Working Group (WG5). It may also be downloaded as a PDF file or gzipped PostScript file.
  11. ^ A full list is in the report available at http://www.fortran.bcs.org/2006/ukfortran06.pdfPDF (24. 2 KiB). A kibibyte (a contraction of ki lo bi nary byte) is a unit of Information or Computer storage, established by the International
  12. ^ "Internal Translator (IT) A Compiler for the IBM 650", by A. J. Perlis, J. W. Smith, and H. R. Van Zoeren, Computation Center, Carnegie Institute of Technology
  13. ^ This is not altogether surprising, as Brian Kernighan, one of the co-creators of Ratfor, is also co-author of The C Programming Language.
  14. ^ From Wikiquote:Programming#Fortran. Brian Wilson Kernighan (ˈkɛrnɪhæn the 'g' is silent (born 1942 Toronto, Ontario, Canada) is a Computer scientist who worked at The C Programming Language (sometimes referred to as K&R or the white book) is a well-known Computer science Book In FORTRAN, undeclared variables can be typed according to their first letter, so "God" would be a real variable, under default implicit typing rules.
  15. ^ Lohr, Steve. "John W. Backus, 82, Fortran Developer, Dies", 2007-03-19. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1279 - A Mongolian victory in the Battle of Yamen ends the Song Dynasty in China. Retrieved on 2007-03-20. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1600 - The Linköping Bloodbath takes place on Maundy Thursday in Linköping, Sweden.  
  16. ^ 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).
  17. ^ Hoare, C. A. R. . Hints on Programming Language Design.   in (October 1973) Sigact/Sigplan Symposium on Principles of Programming Languages.  , reprinted in Horowitz. Programming Languages, A Grand Tour, 3rd ed.  . See Risks Digest: Mariner 1, Vol. 9: Iss. 54, 12 Dec 89 (and Risks Digest: "Mariner I -- no holds BARred", Vol. 8: Iss. 75, for what really happened])
  18. ^ X3J3 post-meeting distribution for meeting held at Brookhaven National Laboratory in November 1976.

See also

External links

History

Standards

Tutorials

References

Code repositories

Open source compilers

Non-open source compilers

Graphical libraries/GUI


Testing Frameworks

Miscellaneous

A kibibyte (a contraction of ki lo bi nary byte) is a unit of Information or Computer storage, established by the International

Dictionary

Fortran

-proper noun

  1. (programming languages) A high-level programming language developed in the 1950s for scientific, engineering and numerical computation.
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