FORTRAN 77 TUTORIAL PDF
solving with Fortran 77 using an interactive timesharing computer system. Tutorials. •. Terminal sessions. •. Reading. All work on the course is done in small . The goal of this Fortran tutorial is to give a quick introduction to the most The most common Fortran version today is still Fortran 77, although Fortran 90 is. Fortran 77 Tutorial. Course Outline. Preface · What is Fortran? Fortran basics · How to use Fortran on the Unix computers at Stanford · Variables, types, and.
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File Access from FORTRAN 77 Programs FORTRAN 77 Unformatted I/O for Tape. It assumes you knew and forgot, and is not a tutorial. FORTRAN (FORmula TRANslation), introduced in , was the first high level language. It has since been revised several times. Fortran This manual refers to Fortran 77 as Fortran, except where specific distinctions This manual is intended as a reference manual, rather than a tutorial, and.
Leading zeros are ignored and 0 is not a valid label number. The continuation cards were usually numbered 1, 2, etc. An IBM could be used to copy a program deck and add sequence numbers. Some early compilers, e. Later compilers relaxed most fixed-format restrictions, and the requirement was eliminated in the Fortran 90 standard. Within the statement field, whitespace characters blanks were ignored outside a text literal.
This allowed omitting spaces between tokens for brevity or including spaces within identifiers for clarity. Note the slight visual difference between a comma and a period.
Miscounts were a problem. The main enhancement was to support procedural programming by allowing user-written subroutines and functions which returned values, with parameters passed by reference. Early computer architectures supported no concept of a stack, and when they did directly support subroutine calls, the return location was often stored in one fixed location adjacent to the subroutine code e. Although not specified in FORTRAN 77, many F77 compilers supported recursion as an option, and the Burroughs mainframes , designed with recursion built-in, did so by default.
Since integers are to be processed in this example, the names of the variables start with the letter "I". If A, B, and C cannot represent the sides of a triangle in plane geometry, then the program's execution will end with an error code of "STOP 1".
Otherwise, an output line will be printed showing the input values for A, B, and C, followed by the computed AREA of the triangle as a floating-point number occupying ten spaces along the line of output and showing 2 digits after the decimal point, the. Now obsolete. The compiler could be run from tape, or from a card deck; it used no further tape or disk storage. It kept the program in memory and loaded overlays that gradually transformed it, in place, into executable form, as described by Haines.
Department of Defense , in their conditional approval vote.
Removal was the only allowable alternative to X3J3 at that time, since the concept of " deprecation " was not yet available for ANSI standards. A the calling program. It is the responsibility of the programmer ables m and n were unchanged! The reason for this is that to make sure that the vectors x and y really have been de- only the values of m and n had been copied to the subrou- clared to have length n or more in some other program tine iswap, and even if a and b were swapped inside the unit.
A common error in Fortran 77 occurs when you try subroutine the new values would not have been passed to access out-of-bounds array elements.
FORTAN Code: A Very Old Language for Numerical Computing
We could also have declared the arrays like this: In the above example, call-by-reference was exactly what real x n , y n we wanted. Some variable and change its value. Since the new value will old Fortran 77 programs may declare variable length ar- then propagate back to the calling program with an un- rays like this: expected value, you should never do this unless like our real x 1 , y 1 iswap subroutine the change is part of the purpose of the subroutine.
This is legal syntax even if the array lengths are greater We will come back to this issue in a later section on pass- than one! But this is poor programming style and is ing arrays as arguments parameters. Fortran subprogram calls are based on call by reference. This means that the calling parameters are not copied to the called subprogram, but rather that the addresses of the parameters variables are passed.
This saves a lot of 31 Passing subsections of arrays memory space when dealing with arrays. No extra storage is needed as the subroutine operates on the same memory Next we want to write a subroutine for matrix-vector mul- locations as the calling sub- program. However, you as tiplication.
There are two basic ways to do this, either by a programmer have to know about this and take it into using inner products or saxpy operations. Let us be mod- account. It is possible to declare local arrays in Fortran subpro- A simple code is given below. This cal- culates the expression There are several important things to note here.
Here is a A. The j'th column of A is A 1:m,j.
OpenMP: Parallel Programming for the Processor
This notation says that x and is A 1,j it is not really a pointer, but it may be helpful y are arrays of arbitrary length. The advantage of this is to think of it as if it were.
We know that the next mem- that we can use the same subroutine for all vector lengths. But in general, the use of common blocks should Finally, note that we have stuck to the convention that be minimized. The index i is used as a row index 1 to m while the index j is used as a column index 1 to n. Most Fortran programs handling 33 Example linear algebra use this notation and it makes it a lot easier to read the code!
Suppose you have two parameters alpha and beta that many of your subroutines need. The following example shows how it can be done using common blocks. Another basic vec- statements return end tor operation is scaling, i. They do not need to all have the same type.
Now suppose we have a m by n matrix we want to scale. Note that in this example we could easily have avoided Instead of writing a new subroutine for this, we can simply common blocks by passing alpha and beta as parame- treat the matrix as a vector and use the subroutine scale. However, there are a few cases where there is no other solution. This does not hold in general. Here is a more robust subroutine for scaling a executable statements.
A variable can- subroutine mscale m, n, alpha, A, lda integer m, n, lda not belong to more than one common block. This declaration is equivalent to the previous version that The only way to pass information between subroutines used alpha and beta.
It is recommended that you always we have seen so far is to use the subroutine parameter list. Here is a dreadful example: tines share a large set of parameters.
In such cases one subroutine sub4 some arguments declarations of can use a common block. Notice especially the shorthand nota- Now alpha is the beta from the main program and vice tion for assigning identical values repeatedly.
Tutorial Fortran in PDF
If you see something like this, it is probably a mis- The data statement is performed only once, right before take. For this reason, the data statement is mainly used in the main program and not in subroutines. This example shows how to make Common blocks can include arrays, too.
But again, this sure a matrix is all zeros when the program starts: is not recommended. Of course you can initialize arrays to other values than zero.Punched card codes included no lower-case letters or many special characters, and special versions of the IBM keypunch were offered that would correctly print the re-purposed special characters used in FORTRAN.
While real is often adequat. Z Terminate program. Fortran 6 or Visual Fortran was licensed to Compaq by Microsoft. It was noted that this "might invalidate some existing programs" but that most of these "probably were non-conforming, anyway". Expressions and assignment Constants The simplest form of an expression is a constant. Reflecting punched card input practice, Fortran programs were originally written in a fixed-column format, with the first 72 columns read into twelve bit words.
Retrieved 21 September Here are some integer constants: Otherwise, the columns of the card were divided into four fields:.