Computer Languages for Engineersinfo.statik.uni-due.de/Lehre/CM/CLFE/Scripts/CLFE-SomeSteps.pdf ·...

Computer Languages for EngineersSome Steps

Ernst Baeck

Institute of Baustatik - Baukonstruktion

April 7, 2014

E. Baeck (Uni-DUE) CM-CLFE / General Points 1 / 104

General Points I

1 IntroductionInfrastructureGiant StepsExams

2 Some HistoryThe ComputerThe Language

3 Console StepsSome Windows Commands

4 Bits and BytesBitsBytesWords

E. Baeck (Uni-DUE) General Points 2 / 104

Introduction Infrastructure

Addresses

Lecturer?

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

Lecturer?That’s me, Mr. Baeck

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

Lecturer?That’s me, Mr. BaeckLike the Beatles song get baeck

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

Lecturer?That’s me, Mr. BaeckLike the Beatles song get baeck or like layed baeck

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

Lecturer?That’s me, Mr. BaeckLike the Beatles song get baeck or like layed baeck or like baeckagain.

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

Lecturer?That’s me, Mr. BaeckLike the Beatles song get baeck or like layed baeck or like baeckagain.But please don’t forget the e in that name!

My Office

V15-S03-D03

My eMail

[email protected]

My internal Phone

Addresses

My Office V15-S03-D03

My eMail [email protected]

My internal Phone

Addresses

My internal Phone 2613

Addresses

My internal Phone 2613

Calling the Info.Server

All the stuff of this lecture you’ll find on the info.serverURL: http://info.baustatik.uni-due.de

Calling the Info.Server

All the stuff of this lecture you’ll find on the info.serverURL: http://info.baustatik.uni-due.de

Info.Server — Stepping into CLFE

The root folder of CLFE

The Scripts-folder offers you some useful scripts for the software

The Software-folder offers you the software packages we will use

The remaining folders content the stuff of all previous semesters

SS14 will be created soon!

Info.Server — Stepping into the New Semester’s Folder

The content of the semester you find in

a subfolder for FORTRAN examples

a subfolder for C++ examples,

and a subfolder for the exam project descriptions.

What you see...

We obviously talk about FORTRAN and C++ language and we willtry to implement some nice examples, I hope.

You also will get the software for free, we use in this lecture.

What you see...

We obviously talk about FORTRAN and C++ language and we willtry to implement some nice examples, I hope.

You also will get the software for free, we use in this lecture.

Moodle.Server — Modules and Registration

You can also access the info.server using the moodle platformURL: http://moodle2.uni-due.de//

Follow the link:Fakultat fur Ingenieurwissenschaften/Abteilung Bauwissenschaften/Bauinformatik.... or simple search for CLFE.

You can also access the info.server using the moodle platformURL: http://moodle2.uni-due.de//Follow the link:Fakultat fur Ingenieurwissenschaften/Abteilung Bauwissenschaften/Bauinformatik.

... or simple search for CLFE.

You can also access the info.server using the moodle platformURL: http://moodle2.uni-due.de//Follow the link:Fakultat fur Ingenieurwissenschaften/Abteilung Bauwissenschaften/Bauinformatik.... or simple search for CLFE.

Moodle.Server — CLFE-Module

You will get topical information in the Forum.

Don’t forget to register.

If you want, you use the forum for postings.

Introduction Giant Steps

Languages

FORTRAN 77Very old computer language. Widespreaded language but a realoldtimer with all it’ problems.

FORTRAN 90+Modern extended and down compatible FORTRAN version.

C++A real allrounder and the main language in the LINUX world. Motherof Java, C# and a modern object orientated successor of thelanguage C, which came up with the operating system UNIX.

When will we do this?

We will start with this old FORTRAN, to understand old fashionedsources (like for example the FEAP - package code)

Languages

We will start in November with the FORTRAN 90/95.We will see, that’s easy to mix the old with new one.

Languages

We will start in January with OOP and C++... analyzing profile section values!

Developer Tools

MinGW - Minimalist GNU for WindowsA compiler suite with a FORTRAN and a C++ compiler.The GNU compilers are available for wide range of platforms.Project: http://sourceforge.net/projects/mingw/files/MinGW/

CodeBlocks - IDE-ToolThe IDE originally developed for C and C++.We will use the extend Version for FORTRAN.Project: http://darmar.vgtu.lt/cbdownload

The tools will be available on the Info.Server.You should also check for newer versions on the project site.

Developer Tools

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

The projects can be developed easily using the software we willdevelop in this lecture.

Working groups YES!

Copy and Paste roped parties NO!

What about this?

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

What about this?

One project to implement a root analysis of an arbitrary function usingNewton’s root finder.

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

What about this?

One project to implement a file controlled algorithm to multiply a series ofmatrices.

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

What about this?

... and one project to implement the calculation of profile section valuesusing an object orientated concept in C++ on the base of the thin-walledapproach.

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

What about this?

It’s recommended to work together in small developer groups.

Introduction Exams

Kind of Examn

Written exam

Projects in FORTRAN

Projects in C++

Working groups YES!

What about this?

To avoid the CopyAndPasteEscape everyone will get an individualizedproject.

Introduction Exams

Submission Details

Everything should be developed with the CodeBlocks IDE

The projects should be submitted by eMail to [email protected]

Everything should be packed into one zip file

The zip file should have the following nameCLFE-SS14-[Your Name]-Version[Number].zip

The zip file should content the following components

Every project should be in one folderAll sources and the executable should be copied into the project folder

The project report should be copied into the project folder too.

If not, the submission will not be accepted!

Introduction Exams

Submission Details

Every project should be in one folderAll sources and the executable should be copied into the project folderThe project report should be copied into the project folder too.

Introduction Exams

Submission Details

Introduction Exams

Submission Details

Introduction Exams

Submission Details

Introduction Exams

Submission Details

Introduction Exams

Grading Details

First grading will give you a more detailed overview what to do.

With a second submission you can enhance your grading, if you want.

My personal deadline to submit is one year.

After having graded your projects, the grades will be sent to thePrufungsamt.

Introduction Exams

Grading Details

What about this?

Therefore it’s necessary to have a version number of the submission toavoid chaos.

Introduction Exams

Grading Details

What about this?

You should be read with the submission within one year, if no otherdeadline will be established by the Prufungsamt.

Introduction Exams

Grading Details

What about this?

To be sure, that everything is going well, you should check it by your own.

Some History The Computer

Zuse’s First Computer

Konrad Zuse (1910–1995) was a German civil engineer, inventor andcomputer pioneer. His greatest achievement was the world’s firstfunctional program-controlled Turing-complete computer, the Z3, whichbecame operational in May 1941.

Figure : Konrad Zuse and his computer Z3 [WP]

Zuse’s First Computer

Konrad Zuse (1910–1995) was a German civil engineer, inventor andcomputer pioneer. His greatest achievement was the world’s firstfunctional program-controlled Turing-complete computer, the Z3, whichbecame operational in May 1941.

Figure : Z1 and Z3, Deutsches Museum Munchen [WP] 1

1Only the Z4 — the most sophisticated of his creations — survived World War II.E. Baeck (Uni-DUE) General Points 14 / 104

Today’s Supercomputer

Today’s computers in general have more than one processor. Intels I7 has4 processor cores. And even in smartphones today we have more than oneprocessor core (for example the Samsung S3 has a quadcore processor).

Figure : IBM’s Supercomputer with 250.000 processors [WP]

Performance and Distribution

OP is Operations Per SecondFLOP is FLoating Point Operations Per Second

Results given by the LINPACK benchmark which typically performsL · U decomposition of a large matrix.

Figure : Performance Increase and Supercomputers Distribution [WP]

OP is Operations Per SecondFLOP is FLoating Point Operations Per SecondResults given by the LINPACK benchmark which typically performsL · U decomposition of a large matrix.

Some History The Language

Motivation — Processor-Code

The fibunacci numbers are defined as follows.

fn = fn−1 + fn−2 for n > 2, with f0 = 1 and f1 = 1

The processor code is given below.

1 8B542408 83FA0077 06 B80000 0000 C3832 FA027706 B8010000 00C353BB 010000003 B9010000 008 D0419 83FA0376 078BD98B4 C84AEBF1 5BC3

Motivation — Assembler-Code

1 f i b :2 mov edx , [ esp +8]3 cmp edx , 04 j a @f5 mov eax , 06 r e t7 @@:8 cmp edx , 29 j a @f

10 mov eax , 111 r e t12 @@:13 push ebx14 mov ebx , 115 mov ecx , 116 @@:17 l e a eax , [ ebx+ecx ]18 cmp edx , 319 j b e @f20 mov ebx , ecx21 mov ecx , eax22 dec edx23 jmp @b24 @@:25 pop ebx26 r e t

First Language — First Compiler — First Bug

First Compiler was written by Grace Murray Hopper in 1952 for A-O.

Hopper is also regarded as the mother of the language COBOL

From her we have the first documented computer bug.

Life was simple before World War II. After that, we had systems.

So we have a lot to do! We will create bugs and will delete them!

Who is Who?

Grace Hopper started to work withthe MARK I computer. On the leftyou see her in front of a UNIVAC I.

What about that...?

COBOL (COmmon Business Oriented Language) was developed in 1960.

First Compiler was written by Grace Murray Hopper in 1952 for A-O.Hopper is also regarded as the mother of the language COBOLFrom her we have the first documented computer bug.Life was simple before World War II. After that, we had systems.

What about that...?

Grace Hopper had some problemswith bugs in the MARK II relaycomputer. She coined the term bugfor faults. Therefore we today areusing the term debugging to finderrors in our code.She said: First actual case of bugbeing found!

What about that...?

One of the debuggers we can use inweb development is called Firebug.This debugger is developed for thefirefox browser, to check websources.

What about FORTRAN

The first version of FORTRAN was released in 1957.

Developed by John W. Backus at IBM for the IBM-704 system.

The first standardized version was FORTRAN 66 or FORTRAN IV.

Next milestone in 1977 with FORTRAN 77.

What about that...

FORTRAN(short for FORmula TRANslator)enabled a computer to perform arepetitive task from a single set ofinstructions by using loops. Thefirst compiler which was able tocompile mathematical formulas intomachine code.

What about FORTRAN

What about that...

The IBM 704 is the firstmass-produced computer withfloating point arithmetic hardware,introduced by IBM in 1954. SoFORTRAN to use it was the nextlogical step forward.

What about FORTRAN

What about that...

The new ISO (International Organization for Standardization) standardwas published in 1966, and was known accordingly as FORTRAN 66, itwas the first HLL (High Level Language) standard in the world.

What about FORTRAN

What about that...

FORTRAN 77 comes with new features which made it possible to applythe concept of structured programming in FORTRAN too.

What about FORTRAN

What about that...

FORTRAN 90 comes with new features which made it possible to applythe concept of object orientated programming.

What about C++

Developed by Bjarne Stroustrup starting in 1979 at Bell Labs.

C++ extends C with object oriented features, such as classes.

Most of the UNIX/LINUX system is written in C.

The C/C++ GCC compiler is the main development tool of theLINUX system.

What about that...

Stroustrup set out to enhance theC language with Simula-likefeatures. Simula is considered thefirst object-oriented programminglanguage and takes a lot of Algol60.

What about C++

What about that...

Ken Thompson and Dennis Ritchieare considered fathers of C. Theydeveloped C working on the UNIXOS at Bell Labs. C comes in theALGOL tradition with facilities forstructured programming.

What about C++

Console Steps Some Windows Commands

What about the Console

You can start the console window with the command cmd.

Then you’ll see the console window with it’s prompt.

What about that...

On Windows 7 you can start theconsole window, clicking on theStart button on the main toolbar atthe screen’s bottom left.Then the command cmd should betyped into the edit and be closed bythe enter key.

What about the Console

You can start the console window with the command cmd.

Then you’ll see the console window with it’s prompt.

What about that...

On Windows 7 you’ll get a window,which is showing you the Windowsversion and the user, who asexecuted the command. By defaultthe prompt will show you yourstandard home directory.

... and what about it’s Commands

With the command c: you select the c-drive.

To select a specific folder you use the command cd .

To list the content of a folder you use the command dir .

To list the content of a file you use the command type.

And don’t forget: Every command has a lot of parameters!

What about that...

A relative jump can be performedwithout the leading back slash. Anabsolute jump starts with a leadingback slash. By default the currentfolder path is viewed by the prompt.

What about that...

The command shows a list ofall files in the current folder.A file’s attributs and size islisted by default.

What about that...

The dir command’s output ispiped with the > operatorinto a text file. The secondcommand shows how to showthe content of the new textfile.

What about that...

A list of all command’s parameter you get with the commandhelp [command name].

... and some Commands more

To delete a file or a group of files you use the command del.

To create a new folder you use the command mkdir.

What about that...

The first dir shows 2files in the folder. Thedel commandremoves the filedir.lst. This is shownby the second dir.

... and some Commands more

To delete a file or a group of files you use the command del.

To create a new folder you use the command mkdir.

What about that...

The first dir showsthe content of thefolder. The mkdir

command creates thenew folder test. Thesecond dir shows thecreated folder.

Bits and Bytes Bits

The Bit

The Bit is the elementary unit of the informatics.

John W. Tukey is supposed to coin in 1946 the word bit.

In 1948 Claude Shannons published the paper A Mathematical Theoryof Communication. In this paper the word bit was used the first time.

George Boole used the bit as a truth value. We know him from hisboolean algebra, which he developed in 1854.

Bits and Bytes Bits

The Bit

Bits and Bytes Bits

The Bit

Bits and Bytes Bits

The Bit

Bits and Bytes Bits

The Bit and it’s Prafixes

SI Prefixes

Name Symbol Value

Kilobit kbit 103

Megabit Mbit 106

Gigabit Gbit 109

Terabit Tbit 1012

Binary Prefix according to IEC

Name Symbol Wert

Kibibit Kibit 210

Mebibit Mibit 220

Gibibit Gibit 230

Tebibit Tibit 240

Bits and Bytes Bits

SI Prefixes

Name Symbol Value

Kilobit kbit 103

Megabit Mbit 106

Gigabit Gbit 109

Terabit Tbit 1012

Name Symbol Wert

Kibibit Kibit 210

Mebibit Mibit 220

Gibibit Gibit 230

Tebibit Tibit 240

Bits and Bytes Bits

SI Prefixes

Name Symbol Value

Kilobit kbit 103

Megabit Mbit 106

Gigabit Gbit 109

Terabit Tbit 1012

Name Symbol Wert

Kibibit Kibit 210

Mebibit Mibit 220

Gibibit Gibit 230

Tebibit Tibit 240

Bits and Bytes Bits

SI Prefixes

Name Symbol Value

Kilobit kbit 103

Megabit Mbit 106

Gigabit Gbit 109

Terabit Tbit 1012

Name Symbol Wert

Kibibit Kibit 210

Mebibit Mibit 220

Gibibit Gibit 230

Tebibit Tibit 240

Bits and Bytes Bits

SI Prefixes

Name Symbol Value

Kilobit kbit 103

Megabit Mbit 106

Gigabit Gbit 109

Terabit Tbit 1012

Name Symbol Wert

Kibibit Kibit 210

Mebibit Mibit 220

Gibibit Gibit 230

Tebibit Tibit 240

Bits and Bytes Bits

Strange Values of Volumn Size

How can I understand the value given in GB of the volumen size?

We have to apply the IEEE prefix for GB! That means divide it by 230.

Oh! It’s hard to implement an open loop!

Bits and Bytes Bits

Strange Values of Volumn Size

How can I understand the value given in GB of the volumen size?

We have to apply the IEEE prefix for GB! That means divide it by 230.

The left value is given in Bytes.The right value is given in GiBytes.

735462813696

230= 684

Bits and Bytes Bytes

The Byte

Bits are subsumed under Bytes.

Originally the number of bits in a byte are given to code onecharacter of a text.

The Telex (TELeprinter EXchange) usesd 5 bits within one byte.

Since the IBM-PC was released 8 bits are used for one byte.

The Byte

This is not an organ...

Telex, the internet of ourgrandfathers.

The Byte

Abraham of the computer century...

5150 or PC was released in1985. The PC was based on theIntel processor 8086. A typicalcomputer office at the middle ofthe 1980s.

Bits and Bytes Words

The Word

A word subsume one or more bytes. A word is used for a logical unitin programming.

A word is used to store data within a program. It’s the elementaryunit of a computer program.

Integer numbers are stored within 1, 2, 4 or 8 byte words.

A floating point number is stored within an 4 or 8 byte word.

The Word

And...

The indivisible atom also isdividable into some smallerparticles, the electrons, the protonsand the neutrons.

The Word

But...

The availability is often depending on the platform. On a 32-bit platformthere are no 8 byte integers supported by the hardware. 1 byte are 2hex-digits, 2 bytes are 4 and 4 bytes are 8 hex-digits. 1 byte are 3octal-digits, 3 + 3 + 2 ⇒. So we would loose 1 bit.

The Word

Using floats everything is different according to IEEE...

sign bit (bit 31)

exponent (bit-23 to bit-30)

mantissa (bit-0 to bit-22)

Introduction into FORTRAN I

5 The GFORTRAN Compiler

6 Famous HelloGet Started with FORTRAN 77Get Started with FORTRAN 90

7 FormatsPunch Card FormatModern Free Style Format

8 Data TypesBasic Data TypesFORTRAN 77 Data TypesFORTRAN 90 Data Types

9 OperatorsArithmetic OperatorsBoolean Operators

10 Explicit LoopsE. Baeck (Uni-DUE) Introduction into FORTRAN 30 / 104

Introduction into FORTRAN II

Archaic LoopFactorial and 66-LoopThe 77 LoopThe 90 Loop

11 BranchingThe 66 BranchingThe 90 Branching

12 Implicit LoopsArchaic Open Loop90’s Simple Open LoopThe Float Precision

13 Subroutines and Functions77 Subroutines and Functions90 Subroutines and Functions

14 ArraysE. Baeck (Uni-DUE) Introduction into FORTRAN 31 / 104

Introduction into FORTRAN III

FORTRAN 77 ArraysFORTRAN 90 ArraysScalar ProductAllocatable ArraysAutomatic Arrays

15 FilesFile CommandsOpen CommandsError HandlingWrite to a FileFormat SpecifierFormat LoopsRead from a FileClose Commands

16 EvaluationsE. Baeck (Uni-DUE) Introduction into FORTRAN 32 / 104

Introduction into FORTRAN IV

77’s Deficiency

E. Baeck (Uni-DUE) Introduction into FORTRAN 33 / 104

The GFORTRAN Compiler

Using the GFORTRAN

Within the first try we will start the gfortran from the console window.

The first parameter should give the source file(s), with the option -o

[Name] we will specify the name of the executable.

but...

A little batch-file, to make it easier to handle. The first line adds thecompiler’s path, the second line adds the editors path. Don’t use quotesfor a path that contains space characters.

path = %path%;c:\program files (x86)\MinGW\bin;

path = %path%;c:\program files (x86)\PsPad Editor;

Using the GFORTRAN

The compiler is not very verbose. We get only some comments, ifthere are some errors in the code.

Column based 77-like formatting is supposed by standard using thesource file extension for.

Free style formating, i.e. 90-like formatting, is supposed by standardusing the source file extension f90.

and then...

If the path is established we simply run the compiler for our little hello.forfile, which will tell as a hello in FORTRAN77 style.

gfortran hello.for -o hello.exe

Using the GFORTRAN

Famous Hello

Famous Hello Get Started with FORTRAN 77

How to get started with FORTRAN77

A FORTRAN77 code is a list of statements and comments.

The column based format has to be used.

No specific start statement is needed.

A FORTRAN77 source is closed with the end statement.

This is shown by the famous Hello World application.

Within a program first we specify then we execute.

How to print the famous Hello...

c23457

write(*,*)"Hello World!"

Which parts we have?

specification part

execution part

end to close the program

The source in general is coded in free style format.

A program is started with program and a name.

A program is closed with end program and it’s name.

77 code can be mixed with a 90 code.

How to print the famous Hello...

! this is fortran 90!

! free style

program hello90

write(*,*) "Hello World!"

end program hello90

Which parts we have?

program [name] ⇒ to open the program

specification part

execution part

part for internal sub programs

end program [name] to close the program

Formats

Formats Punch Card Format

FORTRAN old Style Formatting

FORTRANs format was developed in 1954. It is column based and itcame the the development of the punch card. One card is exactly oneline of code.

Today we see the influence of our history in the standard with of theconsole window which is also 80.

it has started with the punch card...

Column 1-5 is the label range.Column 6 is used for acontinuation character. Column7-72 is used for the programstatements and column 73-80are used for card comments likea card number.

FORTRANs format was developed in 1954. It is column based and itcame the the development of the punch card. One card is exactly oneline of code.

Today we see the influence of our history in the standard with of theconsole window which is also 80.

How to punch a card?

The typical puncher waspresented by IBM. The frontendlooks like a type writer.

Therefore we have to be very careful with the usage of the columns.If a statement runs out of the coding section, the statement will betruncated by the borderline.

If you are storing your source code on punch cards, you will need a lotof storage space.

Let’s have a look into a hello77.for!

c234567

write(*,*) "Hello CLFE!"

Therefore we have to be very careful with the usage of the columns.If a statement runs out of the coding section, the statement will betruncated by the borderline.

If you are storing your source code on punch cards, you will need a lotof storage space.

How to store the punch cards? Isn’t it a giant cloud?

If you want to store your sources froma CD on punch cards you would need agiant warehouse.

Problems with FORTRAN77 Formatting

Truncation of code, which runs out of its range is very dangerous.

Because we only have very little space, we can not indent code blocks.

Problems with FORTRAN77 Formatting

Truncation of code, which runs out of its range is very dangerous.

Because we only have very little space, we can not indent code blocks.

Characters and Restrictions

A comment line starts with a C in the first column.

If you want to continue a line, you put a character which is not aspace character into the 6th column of the following line.

FORTRAN comes with only capital letters. Therefore today’sFORTRAN sources sometimes are written in only capital letters too.

The length of a name was restricted to only 6 characters.Today you can use more than 6 characters.

The fixed Column Format

One of the most frequent errors of beginners are column errors!

The best is, to visualize the regions within the editor.

Labels are given by numbers from 1 to 99999, no strings

Columns Remarks

01 - 05 Columns for label numbers (1 to 99999). Column 1 is alsoused to set comment lines.

06 Column 6 marks a continuation line for the previous line. Themark character can be every character of the FORTRAN char-acter set but not zero or a blank. By default there are up to19 continuation lines available.

07 - 72 Columns for statements.73 - 80 Comment Columns. And are used in the days of the punch

cards as card number field.

Columns Remarks

FORTRAN 77 Character Set

The character set of FORTRAN 77 is the following.2

upper case letter A - Z

10 digits 0 - 9

the 12 special characters: + - * / = ( ) : , . ’ $ and the spacecharacter.

FORTRAN is not case sensitive!

2Modern FORTRAN 77 compiler support also lower case letters.E. Baeck (Uni-DUE) Introduction into FORTRAN 44 / 104

10 digits 0 - 9

Formats Modern Free Style Format

Modern FORTRAN Formatting

Modern FORTRAN formatting is free of column restrictions.Formatting is like in every modern language.

A comment is started by a ! character. The code at the right side ofthe ! will be totally ignored by the compiler.

The problem with the continuation line is solved by appending a &character to the end of a code line.

Let’s have a look into a hello90.f90!

! Comments with "!" instead of c

write(*,*) "Hello 90-World ", & ! 1st line

"and CLFE-Fans" ! 2nd line

The character set of FORTRAN 90/95 is the following.3

lower case letter a -z

10 digits 0 - 9

Miscellaneous common symbols, such as+ - * / = ( ) : , . ’ $ ” { } [ ] !

and any special letter of symbol required by the language,such as a, o, u.

3The ASCII coding system which is used in computing stores one character in onebyte. So ASCII is able to code maximal 256 characters. To support languages with morethen 256 characters the Unicode coding, a multibyte coding, was developed, which isalso supported by the actual FORTRAN 90/95.

10 digits 0 - 9

Data Types

Data Types Basic Data Types

General Aspects

Integer data types are platform depended.

Floats are called REAL in FORTRAN.

A string data type is not available.We have to use arrays of characters.

Type Size RestrictionINTEGER 2 Bytes Range −215 · · · 215 − 1 = 32767INTEGER 4 Bytes Range −231 · · · 231 − 1 = 2147483647 ≈ 2.14 · 109

INTEGER 8 Bytes4 Range −263 · · · 263 − 1 = 9, 22 · 1018

REAL 4 Bytes Exponent range −38 · · · 38, 7 digits precisionREAL 8 Bytes Exponent range −308 · · · 308, 15 digits precisionCHARACTER 1 Byte one byte character

4The maximum INTEGER often is given by the width of the Operating System.So in this case we need a 64 bit OS

General Aspects

Negative Numbers

Negative numbers can be represented by the b-complements.

The sum of a digit and it’s complement is the digit’s maximum value.

This would be 1 within the binary system.

We have to add 1 to the complement to get the b-complement.

Negative Numbers

Comments0000|01112 0716, the positive number has the value 71111|10002 FA16, number complement of 7, 1 -digit

+ 12 b-complement = complement +11111|10012 b-complement or negative number

Check of the b-complement to be the searched negative number0000|01112 positive number

+ 1111|10012 b-complement or negative number1|0000|00002 The overflowing bit will be truncated, so it’s ok.

Data Types FORTRAN 77 Data Types

FORTRAN 77 Standard Data Types

FORTRAN 77s standard data types are a little bit sparse.

The sizer option often is able to extend data types.

The sizer option specifies the number of bytes to use.

So we get INTEGER*1, INTEGER*2, INTEGER*4.

DOUBLE PRECISION is also available as REAL*8.

Type Comment ExampleINTEGER Integer number 15, -100, 2500REAL Floatingpoint num-

ber, single precision3.1415, -5.5, .7E3, 12.5E-5

DOUBLE PRECISION Floatingpoint num-ber, double precision

3.1415D0, -5.5D0, .7D3,12.5D-5

COMPLEX Complex numbers,(two REALs)

(3.1415, -5.5), (1.4, 7.1E4)

LOGICAL Logical values .TRUE., .FALSE.

3.1415D0, -5.5D0, .7D3,12.5D-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415D0, -5.5D0, .7D3,12.5D-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415D0, -5.5D0, .7D3,12.5D-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415D0, -5.5D0, .7D3,12.5D-5

(3.1415, -5.5), (1.4, 7.1E4)

How to Declare Variables in FORTRAN 77

A variable is declared implicit by an assignment.

A variable is declared explicit by it’s data typetype [variable name]

How to declare implicit?

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i to n integer, else real⇐ integer because it starts with i

⇐ real*4 because it starts with r

A variable is declared implicit by an assignment.

A variable is declared explicit by it’s data typetype [variable name]

How to declare explicit?

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integer i

real r

⇐ declaring the integer⇐ declaring the real

FORTRAN 90 data types are like the 77 types.

The sizer option also is available in 90.

real types are platform dependent.

With the kind option the real can be specified.

ber, variable preci-sion

3.1415, -5.5, .7E3, 12.5E-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415, -5.5, .7E3, 12.5E-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415, -5.5, .7E3, 12.5E-5

(3.1415, -5.5), (1.4, 7.1E4)

3.1415, -5.5, .7E3, 12.5E-5

(3.1415, -5.5), (1.4, 7.1E4)

A variable is declared explicit by it’s data typetype::[variable name]

A real can be specified by a type specifier.

The kind specifier is dependent on the platform.

On Intel kind=4 provides a 4 byte float, kind=8 an 8 byte float.

How to declare implicit? Real type on Intel processors

integer::a ! it’s a standard integer

real::b ! it’s a standard real

real(4)::r4 ! it’s 4 byte real

The kind will control the available precision!

real(kind=4)::r4 ! kind=4 often provides a 4 byte real

real(kind=8)::r8 ! kind=8 often provides a 8 byte real

Complex Arithmetic, Quadratic Equation

A complex data type is like a vector of dimension two.

An assignment looks like c = (xr , xi ), i.e. (real,imaginary) part.

Intrinsic functions like sqrt are able to handle the complex.

Solving a quadratic equation with a complex arithmeticprogram csqrt

complex::x,a,b,c

a = (1,0); b = (0,0); c = (4,0);

x = (-b +sqrt(b**2 -4.*a*c))/(2.*a)

write(*,*) x

end program csqrt

⇐ declaring the complex⇐ initialization⇐ apply like real

complex::x,a,b,c

a = (1,0); b = (0,0); c = (4,0);

x = (-b +sqrt(b**2 -4.*a*c))/(2.*a)

write(*,*) x

end program csqrt

complex::x,a,b,c

a = (1,0); b = (0,0); c = (4,0);

x = (-b +sqrt(b**2 -4.*a*c))/(2.*a)

write(*,*) x

end program csqrt

Operators

Operators Arithmetic Operators

Arithmetic Operators of FORTRAN 77

You should be careful with the usage of data types.

Applying integer division will truncate the division rest.

Operator Comment Example+ sum operator x = 2+3 >>> 5

- subtraction operator x = 4-2 >>> 2

* product operator x = 2*4 >>> 8

/ division operator x = 9/2 >>> 4

x = 9./2. >>> 4.5

** power operator x = a**2

// concatenate of strings x = "hello"//"world"

>>> "hello world"

Operators Arithmetic Operators

Arithmetic Operators of FORTRAN 77

You should be careful with the usage of data types.

Applying integer division will truncate the division rest.

Operator Comment Example+ sum operator x = 2+3 >>> 5

- subtraction operator x = 4-2 >>> 2

* product operator x = 2*4 >>> 8

/ division operator x = 9/2 >>> 4

x = 9./2. >>> 4.5

** power operator x = a**2

// concatenate of strings x = "hello"//"world"

>>> "hello world"

Operators Boolean Operators

Boolean Operators of FORTRAN 77

Boolean operators are very special in FORTRAN 77.

Boolean stuff is put in between two dots.

With FORTRAN 90 the standard operator notation is introduced.

Operator Comment Example.lt. less than x = 23 .lt. 13 >>> .false.

.le. less equal x = 23 .le. 23 >>> .true.

.gt. greater x = 23 .gt. 13 >>> .true.

.ge. left shift of bits x = 23 .ge. 23 >>> .true.

.eq. equal x = 23 .eq. 23 >>> .true.

.ne. not equal x = 23 .ne. 13 >>> .false.

.eq. equal x = 23 .eq. 23 >>> .true.

FORTRAN 90 uses nearly the operator symbols like C.

The not equal /= is different because ! is used as comment symbol.

Operator Comment Example< less than x = 23 < 13 >>> .false.

<= less equal x = 23 <= 23 >>> .true.

> greater x = 23 > 13 >>> .true.

>= left shift of bits x = 23 >= 23 >>> .true.

== equal x = 23 == 23 >>> .true.

/= non equal x = 23 /= 23 >>> .false.

FORTRAN 90 uses nearly the operator symbols like C.

The not equal /= is different because ! is used as comment symbol.

Operator Comment Example< less than x = 23 < 13 >>> .false.

<= less equal x = 23 <= 23 >>> .true.

> greater x = 23 > 13 >>> .true.

>= left shift of bits x = 23 >= 23 >>> .true.

== equal x = 23 == 23 >>> .true.

/= non equal x = 23 /= 23 >>> .false.

Boolean Operators for Expressions

The boolean operators for expressions are not depending on theFORTRAN level.

Operator Comment Example.and. logical and x = 1 .lt. 2 .and. 2 .lt. 3 >>> .true.

.or. logical or x = 1 .lt. 2 .or. 2 .gr. 3 >>> .true.

.equ. logical equal x = .true. >>> y = .false.

>>> x .eqv. y >>> .false.

.nequ. logical no equal x = .true. >>> y = .false.

>>> x .neqv. y >>> .true.

.not. logical not x = .not. (1 .lt. 2) >>> .false.

Explicit Loops

Explicit Loops Archaic Loop

Old Fashion FORTRAN 66/IV Loop

A loop starts with do

The label (in this case 100) specifies the last line of the code block.

The loop index is set to the starting value (istart).

The loop runs until the end value (iend) is reached.

After each cycle the loop index is incremented by the step width inc.

If inc is not specified, 1 is used.

Oh! That FORTRAN66 is very archaic!

c234567

do 100 index = istart, iend, inc

Block of statements

100 continue

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Block of statements

100 continue

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Block of statements

100 continue

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Block of statements

100 continue

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Block of statements

100 continue

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Block of statements

100 continue

Escape a 66/IV Loop

To break a loop you only can jump out using a goto.

If the program should stop without ending the loop, a stop or returncan be used.

Breaking a 66 Loop

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do 100 i = 1,10

write(*,*) ’ i=’,i

if (i.eq.5) goto 200

100 continue

200 continue

The loop will be broken, if ireaches 5. Then executing the gotothe program will continue at level200.

Escape a 66/IV Loop

Breaking a 66 Loop

c234567

do 100 i = 1,10

write(*,*) ’ i=’,i

100 continue

200 continue

Explicit Loops Factorial and 66-Loop

Factorial, a FORTRAN 66/IV Example

Implementation of the factorial for a given number n.

The formula is given below.

n! = 1 · 2 · · · · · (n − 1) · n =n∏

We use the loop index i to run the loop.

The range of i is given from 1 to n.

The result variable should be initialized with one, because a productwill be performed in every iteration.

n! = 1 · 2 · · · · · (n − 1) · n =n∏

Implementation of the factorial for a given number n.The formula is given below.

n! = 1 · 2 · · · · · (n − 1) · n =n∏

Here the source code is given without any comments.

c234567

real*4 f

integer*2 i,n

input data

n = 20

do 100 i=2,n

f = f*i

100 continue

The comment line shows the numbers of thecolumn. With every statement starts with thecolumn 7.

f, the result variable, gets a new factor withinevery iteration step.

The label 100 must be inside the label columns1-5.

Explicit Loops The 77 Loop

77 Loop, only one Step into the Future

The end of the loop is defined by an end do statement.

If you want to break the loop there is no any possibility but goto.

Oh! With FORTRAN77 only on step into the future. That label is missing!

c234567

do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

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do i = 1,10

write(*,*) ’ i=’,i

200 continue

Escape and cycle a 77 Loop

We cycle with the label 100 and exit with label 200

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do i = 1,10

write(*,*) ’ i=’,i

100 continue

200 continue

The loop will be cycled, if i isequal 2.

We cycle with the label 100 and exit with label 200

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do i = 1,10

write(*,*) ’ i=’,i

100 continue

200 continue

The loop will be cycled, if i isequal 2.

90 Loop with modern Features

FORTRAN 90 escapes a loop with the exit statement.

FORTRAN 90 starts a new cycle immediately with a cycle statement.

Now the Loop is up to date!

! free style format

do index = istart, iend, inc

Block of statements

! free style format

Block of statements

! free style format

Block of statements

! free style format

Block of statements

! free style format

Block of statements

! free style format

Block of statements

! free style format

Block of statements

! free style format

Block of statements

To break a loop in FORTRAN 90, we exit with the exit statement.

To cycle a loop in FORTRAN 90, we use the cycle statement.

With FORTRAN 90 structured programming is possible.

Structured programming avoids goto jumping ...

and so called spaghetti code.

Breaking and escaping 90 Loops

! free style format, no goto-jumps

do i = 1,10

if (i.eq.2) cycle

write(*,*) ’ i=’,i

if (i.eq.5) exit

The loop will be cycled with cycle,if i is equal 2. The loop will bebroken with exit, if i reaches 5.

do i = 1,10

if (i.eq.2) cycle

write(*,*) ’ i=’,i

if (i.eq.5) exit

do i = 1,10

if (i.eq.2) cycle

write(*,*) ’ i=’,i

if (i.eq.5) exit

do i = 1,10

if (i.eq.2) cycle

write(*,*) ’ i=’,i

if (i.eq.5) exit

do i = 1,10

if (i.eq.2) cycle

write(*,*) ’ i=’,i

if (i.eq.5) exit

Branching

Branching The 66 Branching

Branching in FORTRAN 66

Branching is done with an IF statement.

if (boolean expression) statement

Multiple statement branching only is possible with jumps.

Two branches are done two goto jumps.

Skip it by a goto jump...

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if (.not. condition1) goto 100

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

100 continue

Double Branching and wild jumping, typical for FORTRAN 66...

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if (condition1) goto 100

.. else code block ..

goto 200

100 continue

.. if code block ..

200 continue

Branching is done with an if, then, endif statement.

if (boolean expression) then starts the Branch.

Then we can option execute a code block.

The branch is closed with an endif statement.

endif and end if is the same.

Time of jumping with goto can be over...

! this is free styling format

if (condition1) then

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

end if

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

end if

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

end if

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

end if

.. statement 1 ..

.. statement 2 ..

.. statement 3 ..

end if

Mulitbranching in FORTRAN 90

Multibranching is done with an else statement.

More then one condition are possible with elseif.

Both statements are optional.

else has to be the last branch, if used.

Even with multibranching jumping with goto can be avoided...

if (condition 1) then

.. code block 1 ..

elseif (condition 2) then

.. code block 2 ..

.. code block 3 ..

end if

.. code block 1 ..

.. code block 2 ..

.. code block 3 ..

end if

.. code block 1 ..

.. code block 2 ..

.. code block 3 ..

end if

.. code block 1 ..

.. code block 2 ..

.. code block 3 ..

end if

Solving a Quadratic Equation with FORTRAN 66 and 90

Branching is necessary to handle every case.

a · x2 + b · x + c = 0

If a 6= 0 we have the quadratic case.

If a = 0 ∧ b 6= 0 we have the linear case.

If a = 0 ∧ b = 0 we have the constant case.

If a = 0 ∧ b = 0 ∧ c = 0 we have infinite solutions.

If a = 0 ∧ b = 0 ∧ c 6= 0 we have no solutions.

... so, let’s implement it in FORTRAN 66!

... then we will see how it works on FORTRAN 90!

a · x2 + b · x + c = 0

Implicit Loops

Implicit Loops Archaic Open Loop

No Statement for an Open Loop in FORTRAN 66/IV

An implicit loop in contrast to an for has to be controlled explicitly.

That is, an endless loop with an explicit break condition.

In FORTRAN 66/IV there is no statement for an implicit loop.

Therefore we have to solve the problem with jumps.

... an endless and lively source of gotos will make everythingincomprehensible. Strategy is like programming in assembler!

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100 continue

.. some statements ..

if (condition) goto 200

goto 100

200 continue

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100 continue

goto 100

200 continue

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100 continue

goto 100

200 continue

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100 continue

goto 100

200 continue

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100 continue

goto 100

200 continue

Implicit Loops 90’s Simple Open Loop

FORTRAN 90 Comes With a Modern Loop Statement

If we use the do without indexing, it’s an endless loop.

The endless loop can be broken with an exit.

So, like in every modern language, now it looks very comprehensible.

Wonderful!, The pain has gone!

! this is free style format

... some statements ...

if (condition) exit

... some statements...

end do

if (condition) exit

end do

if (condition) exit

end do

Implicit Loops The Float Precision

Example: Determining the Float Precision

How can we determine the arithmetic precision of a float?

To calculate the relative precision, we should know,that a float has an finite number of digits.

So we start from a value of 1.

Then we divide it by 2.

This we do as long as the result is differentcomparing it with the previous result.

If the current value is equal to the previous withrespect to the finite digits, We have to multiplythis value by 2.

So that is the smallest relative deviation, we candescribe with our float.

You can see easily that the implementation will usean implicit loop.

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

x1 = 1.x2 = 1.d = 2.

x2 = x2/ds = x1 + x2

s = x1

result =x2 ∗ d

Subroutines and Functions

Subroutines and Functions 77 Subroutines and Functions

subroutine and function encapsulate source code.

Parameter are passed from the caller by the list of formal parameters.

Parameters are passed by reference, i.e. by there address.

Passing by reference provides working on the caller’s memory.

Passing parameter by reference can produce undesired side effects.

A function provides a return value, a subroutine not.

There are no other differences.

A subroutine in C would be a void function.

Interface, List of Parameters

Data are passed to the called sub programs by the parameter list.

A parameter list, is a comma separated list of names.

Parsed parameters are specified like other parameters in thespecification section of the sub program.

A function return value is assigned to the name of the function.

Parameter names are formal. Only the order and the type areimportant.

Wrong orders and wrong types of parsed parameters i.g. will crashthe program.

The compiler is not able to check parameter parsing.

Syntax and an Example of a Subroutine

A subroutine starts with a name, the end is end.

return starts the jump back to the caller.

Add two reals in a subroutinec234567

real s

call AddIt(1.,2.,s)

write(*,*) s

c here is the subroutin

subroutine AddIt (a,b,c)

real a,b,c

c = a+b

return

⇐ variable for the return⇐ call the subroutineinput values are 1 and 2

⇐ subroutine’s interface⇐ all parameters are real⇐ the third is the return⇐ return is possible becauseof the reference parsing

Syntax and an Example of a Subroutine

A subroutine starts with a name, the end is end.

real s

call AddIt(1.,2.,s)

write(*,*) s

subroutine AddIt (a,b,c)

real a,b,c

c = a+b

return

⇐ variable for the return⇐ call the subroutineinput values are 1 and 2

⇐ subroutine’s interface⇐ all parameters are real⇐ the third is the return⇐ return is possible becauseof the reference parsing

Syntax and an Example of a Function

A function starts with a type and a name, the end is end.

The return value is set by assigning it to the name of the function.

write(*,*) AddIt(1.,2.)

real function AddIt (a,b)

real a,b

AddIt = a+b

return

⇐ call the functioninput values are 1 and 2

⇐ function’s interface⇐ all parameters are real⇐ assign return value⇐ and return to the caller

real a,b

AddIt = a+b

return

real a,b

AddIt = a+b

return

Subroutines and Functions in 90

90 functions and subroutines are very similar to the 77 routines.

In 90 style the end of a function/subroutine is signed by it’s name.

90 provides internal function inside a contains block.

A little converter function inside the main program.

Converting C Temperature into Fahrenheit

program intfunc

real::TCel,TFah

TCel = 100.

write (*,*) ’TCel=’,TCel,’TFah=’,CelToFah(TCel)

contains

real function CelToFah(t)

CelToFah = t * 1.8 + 32.0

end function CelToFah

end program intfunc

Arrays

Arrays FORTRAN 77 Arrays

Arrays in FORTRAN 77

Arrays are indexed variables.

Arrays only can store the same data type.

Arrays are data types which are used for vectors and matrices.

An array variable first is declared by the data type.

With an dimension statement the index range is set.

77 only provides static arrays. Dynamical allocation is not supported.

Declaring a 3d unity vector in x direction, 77 version

c23457

real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

⇐ first the type is set⇐ then the array range is set⇐ access with parenthesis

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real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

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real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

c23457

real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

c23457

real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

c23457

real v

dimension v(3)

v(1) = 1.

v(2) = 0.

v(3) = 0.

Behavior of an array is like in FORTRAN 70.

Type specification and array range in one statement

In contrast to 77 there dynamic arrays too.

Automatic array can be allocated in sub programs.

Specifying 90 arrays

real,dimension(3)::a,b

a(1) = 1; a(2) = 2; a(3) = 0

b(1) = 0; b(2) = 3; b(3) = 1

⇐ standard kind used⇐ ; connects lines

a(1) = 1; a(2) = 2; a(3) = 0

b(1) = 0; b(2) = 3; b(3) = 1

a(1) = 1; a(2) = 2; a(3) = 0

b(1) = 0; b(2) = 3; b(3) = 1

a(1) = 1; a(2) = 2; a(3) = 0

b(1) = 0; b(2) = 3; b(3) = 1

Arrays Scalar Product

Scalar Product, an Array 77 Example

A simple array example is given by the scalar product.

The scalar product of two vectors is given by

s = a · b =3∑

ai · bi

s = a · b =3∑

ai · bi

s = a · b =3∑

ai · bi

Implementation of the 77 scalar product

c234567

real a,b,s

dimension a(3),b(3)

do i=1,3

s = s + a(i)*b(i)

end do

⇐ first we declare⇐ then we set up the ranges⇐ here we initialize the vectors⇐ start up calculation

The 90 version only differs in the frame and the array declaration.

Within the vector initialization we connect lines with an ; character.

The 90 version only differs in the frame and the array declaration.

Within the vector initialization we connect lines with an ; character.

Implementation of a scalar product in FORTRAN 90

program scalprod

real::s

a(1) = 1; a(2) = 2; a(3) = 0

b(1) = 0; b(2) = 3; b(3) = 1

do i=1,3

s = s + a(i)*b(i)

end do

write(*,*) s

end program scalprod

⇐ standard kind used⇐ scalar declaration⇐ ; connects lines

Arrays Allocatable Arrays

Allocatable Arrays in FORTRAN 90

In contrast to 77 FORTRAN 90 provides allocatable arrays.

Within a first step the array has to be specified as an allocatable array.

The number of indexes has to be specified.

Within a second step the array has to be allocated.

The available array ranges have to be specified.

If the array is no longer used, the array has to be deallocated.

Allocating an 90 arrayprogram allocmem

real,allocatable, dimension(:)::a

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

end program allocmem

⇐ specify as allocatable

⇐ allocate the array⇐ use the memory

⇐ and release it from memory

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

integer::n = 3

allocate(a(1:n))

a(1)=1; a(2)=2; a(3)=3

write(*,*) (a(i),i=1,3)

deallocate(a)

Arrays Automatic Arrays

Automatic Arrays in FORTRAN 90

An automatic array lives in the scope of a subroutine or a function.

Memory can be automatically allocated by specifying a flexible range.

The allocated memory is released automatically.

An automatical 90 arrayprogram autoarray

call testauto(3)

contains

subroutine testauto(n)

integer::n

real::s=0. ,f(n)

do i=1,n

f(i) = i; s = s+f(i)

end do

write(*,*) s

end subroutine testauto

end program autoarray

⇐ call the test subroutine

⇐ the n is arbitrary

⇐ allocate f as automatic

⇐ use the array

⇐ it’s released in the return

call testauto(3)

contains

integer::n

real::s=0. ,f(n)

do i=1,n

f(i) = i; s = s+f(i)

end do

write(*,*) s

⇐ use the array

call testauto(3)

contains

integer::n

real::s=0. ,f(n)

do i=1,n

f(i) = i; s = s+f(i)

end do

write(*,*) s

⇐ use the array

Files File Commands

File Commands

open opens a file.

write is used to write into a file.

read is used to read from a file.

close is used to close an open file.

Files File Commands

File Commands

open opens a file.

Files File Commands

File Commands

open opens a file.

Files File Commands

File Commands

open opens a file.

Files Open Commands

Open a File

open is controlled by a set of parameters.

Most parameters are optional.

The 1st parameter, an integer, is the unit parameter.

The 2nd parameter specifies the file (file=[filename]).

status specifies the open status.

action specifies the access permissions.

Example to Open a Text File

open (20, file=’myfile.txt’, status=’OLD’, iostat=st)

Files Open Commands

Open a File

Files Open Commands

Open a File

Files Open Commands

Open a File

Files Open Commands

Open a File

Values of the status Option.

status Commentold The file must existnew A new file is created. No file with this name must exist.replace A new file is created. An existing file will be replaced.scratch A temporary file is created, a file name is not needed. if the file

is closed, the file is automatically removedunknown The same as replace. It’s a pre Fortran90 statement and should

be replaced by replace

Files Open Commands

Open a File

Values of the action Option.

action Commentread The file is opened only for read access.write The file is opened only for write access.readwrite This action is set if the parameter is not given. The file is opened

for reading and writing.

Files Error Handling

File Commands General Error Handling

The iostat parameter has to be used.

The io error code is assigned to a variable.

If the io status is equal zero, everything is ok.

Error Handling with iostat

integer st

if (st /= 0) then

write(*,*) ’*** Error: File not found!’

integer st

if (st /= 0) then

integer st

if (st /= 0) then

Files Write to a File

Write to a Text File

write is used to write to text file.

1st parameter specifies the output channel.

2st parameter specifies the output format.

The 2nd parameter can also be used as a link to a format statement.

Optional an error exception can be set by iostat.

Write with Standard Format into the Standard Channel

write(*,*) ’Write to the standard channel, with standard format!’

Write a Value to a Text File with Standard Format

open (10,file=’myfile.txt’,status=’replace’)

write(10,*) ’Write a value:’,value

close(10)

Write a Value to a Text File with Specified Format

write(10,’(a,i2)’) ’Write a value:’,value

close(10)

Write a Value to a Text File with a Format Link

write(10,123) ’Write a value:’,value

123 Format(a,i2)

close(10)

Write a Value to a Text File Checking the iostat

write(10,’(a,i2)’,iostat=st) ’Write a value:’,value

if (st /= 0) then

write(*,*) ’*** Error: can not write to the file!’

close(10)

Files Format Specifier

Format Specifier for Text IOs

The general form of an output format is [m]Tw[.n].

The Format type T

I, integer format.F, float format with fixed decimal point.E, float format with exponential representation.A, text format, the with of the format is optional.X, output of spaces./, a new line, line break.

multiplier m

width of the output field w

number of significant digits n in float format.

Print some Data using Format Specifiers

write(io,’(a2,i3,a2,f10.2)’) ’ a(’,i,’)=’,a(i)

The Format type T

I, integer format.

F, float format with fixed decimal point.E, float format with exponential representation.A, text format, the with of the format is optional.X, output of spaces./, a new line, line break.

multiplier m

The Format type T

I, integer format.F, float format with fixed decimal point.

E, float format with exponential representation.A, text format, the with of the format is optional.X, output of spaces./, a new line, line break.

multiplier m

The Format type T

I, integer format.F, float format with fixed decimal point.E, float format with exponential representation.

A, text format, the with of the format is optional.X, output of spaces./, a new line, line break.

multiplier m

The Format type T

I, integer format.F, float format with fixed decimal point.E, float format with exponential representation.A, text format, the with of the format is optional.

X, output of spaces./, a new line, line break.

multiplier m

The Format type T

I, integer format.F, float format with fixed decimal point.E, float format with exponential representation.A, text format, the with of the format is optional.X, output of spaces.

/, a new line, line break.

multiplier m

The Format type T

multiplier m

The Format type T

multiplier m

The Format type T

multiplier m

The Format type T

multiplier m

The Format type T

multiplier m

Files Format Loops

Format using Loops

To read or write array data FORTRAN supports loops.

A one dimensional loop is done by(var(i),i=start,stop).

A two dimensional loop is done by((var(i,j),i=istart,istop),j=jstart,jend).

Files Format Loops

Format using Loops

Print the Content of an Array using Format Loops

! print a real array

! - setup the format for one row

write(matfmt,’(a,i2,a)’) ’(’,ndim(2),’(f10.3))’

! - iterate all rows

do i=1,ndim(1)

write(io,matfmt) (a(i,j),j=1,ndim(2))

Files Format Loops

Format using Loops

Print the Content of an Array using Format Loops

! print a real array

! - setup the format for one row

write(matfmt,’(a,i2,a)’) ’(’,ndim(2),’(f10.3))’

! - iterate all rows

do i=1,ndim(1)

write(io,matfmt) (a(i,j),j=1,ndim(2))

Files Read from a File

Read from a Text File

Free format reading is done with a * format.

Column bases reading is done by using a format specification.

Read two Values from a Text File, i.e. one Line

open (10,file=’myfile.txt’,status=’old’)

read(10,*) value1, value2

close(10)

Read two Values from a Text File, i.e. one Line

read(10,*) value1, value2

close(10)

Two Float Values are Read from a Table with Column Width 10

read(10,’(2F10.0)’) value1, value2

close(10)

Files Close Commands

Close a File

close is used to close an opened file.

The unit, specified in the open statement, is used in the closestatement.

Opened files have to be closed to avoid a lack of io handles.

Close a File

Evaluations

Evaluations 77’s Deficiency

Deficiencies of pure FORTRAN 77

There are no dynamic storage facilities at all.

There are no user-defined data types or data structures (except theCOMMON block).

Interfaces to functions are not checked, so it will be very error-prone.

Some platform-dependent features remain, so programs are nottotally portable.

Control structures are still very poor, so you have to jump usingGOTO.

Archaic features left over from the punched-card era.

fixed-format lines,statements all in upper-case,

variable names limited to 6-characters.

In practice 77 therefore are used, which will reduce the portability.

fixed-format lines,statements all in upper-case,variable names limited to 6-characters.

FORTRAN Examples I

17 Newtons AlgorithmDie TheorieAlgorithm’s Flow

E. Baeck (Uni-DUE) FORTRAN Examples 101 / 104

Newtons Algorithm

Newtons Algorithm Die Theorie

Newton Scheme to Search for a Root

Newton lays the foundations for most ofclassical mechanics.

Newton developed the differential andintegral calculus.

Let’s discuss his simple formula.

So we search for the root of y = f (x).

The series expansion of f (x) of xn.

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

or we get it from the slope of the triangle:

f ′(xn) =f (xn)

xn − xn+1

Isaac Newton (1643-1726)

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

f ′(xn) =f (xn)

xn − xn+1

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

f ′(xn) =f (xn)

xn − xn+1

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

f ′(xn) =f (xn)

xn − xn+1

Geometrical Interpretation

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

f ′(xn) =f (xn)

xn − xn+1

f (xn+1) = f (xn) + (xn+1 − xn) · f ′(xn) = 0

xn+1 = xn −f (xn)

f ′(xn)

f ′(xn) =f (xn)

xn − xn+1

Newtons Algorithm Algorithm’s Flow

Pseudo-Code of Newton’s Algorithm

1 We start with an arbitrary x .

2 Calculate f (x)

3 If |f (x)| < ε, then we have the result.

4 If the maximum number of trials are expired, no solution found.

5 Calculate f ′(x).

6 If |f ′(x)| < ε, vanishing slope.

7 Calculate next x-value: x ⇐ x − f (x)f ′(x)

8 Start next cycle with step 2.

2 Calculate f (x)

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