Fortran History Versions And Revisions Features And Extensions

The first FORTRAN compiler was developed for the IBM 704 in 1954– 57 by an IBM team led by John W. Backus. This was an optimizing compiler, because the authors reasoned that no one would use the language if its performance was not comparable to assembly language.

The language was widely adopted by scientists for writing numerically intensive programs, which encouraged compiler writers to produce compilers that generate faster code. The inclusion of a complex number data type in the language made Fortran especially suited to scientific computation. There are many vendors of high performance Fortran compilers today. Many advances in the theory and design of compilers were motivated by the need to generate good code for Fortran programs.

Several revisions of the language have appeared, including the well-known FORTRAN IV (also known as FORTRAN 66), FORTRAN 77, and Fortran 90. The most recent formal standard for the language, published in 1997, is known as Fortran 95. IBM's versions were never as popular as those developed by others, which was especially true of FORTRAN IV—WATFOR, the version of FORTRAN IV developed at the University of WaterlooIn Detail) Motto: Concordia cum veritate ( Latin: In harmony with truth Chancellor Mike Lazaridis President David L. Johnston School type Public Religious affiliation Main campus: None Conrad Grebel: Mennonite Renison: Anglican St. Jerome's: Catholic St., Canada, was universally preferred because it produced better reports of compilation errors. The software for automatically generating flow charts from FORTRAN programs was also developed outside IBM.

2 Features and extensions

Initially, the language relied on precise formatting of the source code and heavy use of statement numbers and gotoGOTO is a command found in many programming languages which instructs the computer to jump to another point in the computer program. It is the fundamental operation which can be used for transfer of control from one part of a program to another, and most statements. These quirks have been removed from newer versions of the language. Successive versions also introduced 'modern' programming concepts, such as source code comments and output of text, IF-THEN-ELSE (in FORTRAN 77), recursionIn mathematics and computer science, recursion is a particular way of specifying (or constructing) a class of objects (or an object from a certain class) with the help of a reference to other objects of the class: a recursive definition defines objects in (in Fortran 90), and parallel constructs, while still attempting to maintain Fortran's 'lean' profile and high performance. Among the most popular specialized Fortran-based languages were SASOverview The SAS System is an integrated system of software products (provided by the SAS Institute) that enables the programmer to perform: data entry, retrieval, and management report writing and graphics statistical and mathematical analysis business p, for generating statistical reports, and SIMSCRIPT, for simulating processes involving queuing.

Vendors of high performance scientific computers ( Burroughs, CDCControl Data Corporation or CDC was one of the pioneering supercomputer firms. For most of the 1960s they built the fastest computers in the world, by far, only losing that crown in the 1970s to what was effectively a spinoff. They were well known and hig, CrayCray Research was founded by Seymour Cray in 1972. The company was famous for its supercomputers, starting with the 1976 Cray-1 vector computer. In 1989, Cray Research spun off Cray Computer Corporation separating its Cray 3 product line from the other pr, IBM, Texas Instruments, ...) added extensions to Fortran to make use of special hardware features such as: instruction cache, CPU pipeline, vector arrays, etc. For example, one of IBM's Fortran compilers (H Extended IUP) had a level of optimization which reordered the machine code instructions to keep several internal arithmetic units busy at the same time. Another example is CFD, a special 'version' of Fortran designed specifically for the ILLIAC IV supercomputer, running at NASA's Ames Research Center. These extensions have either disappeared over time or had elements incorporated into the main standard; the major remaining extension is OpenMP, which is a cross-platform extension for shared memory programming. One new extension, CoArray Fortran, is intended to promote parallel programming.

3 Syntax drawbacks and advantages

As what was basically a first attempt at designing a high-level language, the language's syntax is regarded as arcane by many programmers who learned more modern languages. It is difficult to write a lexical analyser for, and one-character mistakes can lead to runtime errors rather than compilation errors if more recent constructs such as free-form source are not used. Some of the earlier versions, particularly, lacked facilities that would be regarded as useful in modern machines, such as dynamic memory allocation.

One should, however, take into consideration that the syntax of Fortran has been tuned to scientific and numerical work, and that many of its deficiencies have been addressed in more recent versions. For example, Fortran 95 has very short commands for performing mathematical operations on matrices and arrays which not only greatly improves program readability but also provides useful information to the compiler to enable it to vectorize operations. For these reasons, Fortran is not often used outside scientific and engineering numerical analysis, but remains the language of choice for high performance numerical computing.

4 Sample program

This program will compile using the Open Watcom open source compiler. The file operations are known to work with DOS/ Windows, but pertinent changes will probably make the code work in other environments as well.

C This program calculates the area of a tank, C excluding the bottom. C The variables are assigned as follows: C C R = RADIUS C H = HEIGHT C PI = 3.14159 C A = AREA C C They are declared with the REAL statement below. REAL R,H,PI,A C The OPEN command associates the data file, "PANDAT.DAT", C in folder "DATA" with logical device 5. If there is an C error, statement 900 is executed. OPEN(5,FILE='C:\DATA\PANDAT.DAT',ACCESS='SEQUENTIAL', ; STATUS='OLD',ERR=900) C This following section accumulates the sum of C the input variables. C The first command reads the data record and C stores it in memory. 10 READ(5,FMT=1,END=99)R,H C The next command describes the form and location C of the data to be read. 1 FORMAT(F4.2,F4.2) C The next statements assign values to the variables. PI=3.14159 A=PI*R**2+2*PI*R*H C The next section writes the sums to the screen. C The first command, PRINT, denotes which FORMAT C statement is to be used, and the variables to be printed. PRINT 11, H,R,A C The following FORMAT statement describes how the C data field is to be written. Notice the semicolon in column 6 C which is used to denote continuation of the previous line. 11 FORMAT(1X,'RADIUS= ',F6.2,10X,'HEIGHT= ',F6.1,10X,'AREA= ', ; F8.1) C The following statement completes the loop. GOTO 10 C The next section prints if the input data is invalid. 900 PRINT 21 21 FORMAT(1X,'INVALID DATA') C Now we close the file and end program execution. 99 CLOSE(5) STOP END

5 References

General:

Nyhoff, Larry; Leestma, Sanford (1995). FORTRAN 77 for Engineers and Scientists with an Introduction to FORTRAN 90. 4th Edition. Prentice Hall. BooksEnthsiast.com.

Standards documents:

ANSI X3.198-1992 (R1997). Title: Programming Language "Fortran" Extended. Informally known as Fortran 90. Published by ANSI.
ISO/IEC 1539-1:1997. Title: Information technology - Programming languages - Fortran - Part 1: Base language. Informally known as Fortran 95. There are a further two parts to this standard. Part 1 has been formally adopted by ANSI.

6 External links

General:

Fortran DMOZ category
USER NOTES ON FORTRAN PROGRAMMING (UNFP)
Unit 7.1 FORTRAN 77 – Part of ASPIRE's textbook in Computational Science
Unit 7.2 FORTRAN 90 – Ditto

Program repositories:

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1 History, versions, and revisions