INTRODUCING FORTRAN 90

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1 INTRODUCING FORTRAN 90

2 Springer Berlin Heidelberg New Yorlc Barcelona Budapest HongKong London Milan Paris Tokyo

3 Ian Chivers and Jane Sleightholme INTRODUCING FORTRAN 90, Springer

4 Ian David Chivers, B.Sc., M.Sc., M.B.C.S. C.Eng. Jane Sleightholme, M.Sc. The Computer Centre King's College, Strand London WC2R 2LS, UK ISBN-13: e-isbn-13: DOl: / British Library Cataloguing in Publication Data Chivers, I. D. Introducing Fortran 90 I. Title II. Sieightholme, Jane Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms oflicences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers. Springer-Verlag London Limited 1995 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that maybe made. Typesetting: Camera ready by authors 34/ Printed on acid-free paper

5 to Joan. Martin and Jenny to Steve. Mark. and Jonathan

6 Preface This book has evolved from our combined experience of working in computing services at the University of London (for the last nine years at King's College, and before that eight years at Imperial College and seven at Chelsea College) in the teaching, advice and technical support of Fortran and related areas. Thanks are due to:- the staff and students at King's College London - without them none of this would have been possible; also the support and facilities provided by the Computer Centre; the patience of our families during the lengthy period required to develop the courses upon which this book is based and whilst preparing the camera ready copy; the staff at NAG, Salford Fortran and DEC for their support. Special thanks to Steve Lionel at DEC and Tim Bartle at Salford for the opportunity to take part in the beta testing of the Alpha compiler and the Salford Nag compiler respectively. The lessons to be learnt from moving programs between the three compilers were invaluable; the people on comp.lang.fortran and the specialist Fortran 90 list. Access to the expertise of several hundred people involved in the use of Fortran on a daily basis across a wide range of disciplines is inestimable; the staff at the BSI, IEC and ISO - Annex D from ISO/IEC 1539:1991 has been reproduced with the permission of the International Organization for Standardization, ISO and the International Electrotechnical Commission, lee. The complete standard can be obtained from any ISO or IEC member or from the ISO or IEC Central offices, Case Postal, 1211 Geneva 20, Switzerland. Copyright remains with ISO and IEC. finally Beverley Ford at Springer Verlag for her infectious enthusiasm and encouragement during the gestation period and birth! The course notes and book were prepared on a range of PCs using a variety of versions of Corel Ventura Publisher. The facilities provided by Ventura are superb, and make the production of firstly the notes and secondly the book straightforward. Whilst Ventura has a slightly steeper learning curve than that of word processing software the investment is quickly repaid in the time and effort saved. Draft output was to a range of Postscript laser printers. Final output was to a Linotron 300 typesetter at the University of London Computer Centre.

7 Preface Tools that proved invaluable were:- EC. This is a programmers screen editor. It is small and extremely fast and provided a very good tool for the development of Fortran programs. Edlin and EDIT are not ideal for this! Xtree Gold. This is a very useful file file management utility for DOS and the PC. Keeping track of approaching a thousand files over two years on a number of PCs is not without problems. Xtree helped out tremendously here. The Mortice Kern Systems Unix Toolkit. This provides UNIX under DOS and Windows on a pc. The pattern matching facilities provided by ED and SED provide a very powerful set of tools for the manipulation of text files. Other tools that proved invaluable include HEAD, TAIL, AWK, SORT, SPELL and the Korn Shell. A range of networking software that made the transfer of the programs and data files between the various hardware platforms easy. Most notably the FTP and Telnet facilities provided by WINQVT over IP, but also Kermit in the days of X 25 connectivity. A range of hardware platforms, operating systems and Fortran compilers were used. These were:- DEC V AX under VMS and later OPEN VMS with the NAG Fortran 90 compiler; IBM PC and compatibles under DOS and Windows using the Salford NAG Fortran 90 compiler; DEC Alpha under OPEN VMS using the DEC Fortran 90 compiler; We are currently in the process of putting all program examples up at King's on our WWW server. The material will be found under:- uk/kis/support/cc/courses but the exact location is not finalised at this time. This material will be made available as simple ASCII text, to minimise compilation problems. New course material is under development and will be put up as and when it is available. Ian D Chivers, i.chivers@kcl.ac.uk Jane Sieightholme, j.sleightholme@kcl.ac.uk 1995.

8 1 Overview Introduction to Computer Systems 2.1 The components of a computer system 2.2 Software. 2.3 Problems Bibliography... 3 Introduction to Operating Systems History of Operating Systems The 1940s The 1950s The 1960s The 1960s and 1970s The 1970s and 1980s 3.2 Networking 3.3 Problems Bibliography... 4 Introduction to Using a Computer System Files Editors Stand Alone Systems 4.4 Networked Systems 4.5 Multi-User Systems 4.6 Other Useful Things to Know 4.7 Bibliography... 5 Introduction to Problem Solving. 5.1 Natural Language 5.2 Artificial Language Notations 5.3 Resume Algorithms Top Down Bottom up Stepwise Refinement. 5.5 Systems Analysis and Design Problem Definition Feasibility Study and Fact Finding Analysis Design Detailed Design

9 5.5.6 Implementation Evaluation and testing Maintenance 5.6 Conclusions 5.7 Problems Bibliography. 6 Introduction to Programming Languages 6.1 Some Early Theoretical Work What is a programming language? Program Language Development and Engineering 6.4 The Early Days Fortran Cobol Algol Chomsky and Program Language Development 6.6 Lisp Snobol Second Generation Languages PL/l and Algol Simula Pascal APL Basic. C.. Some Other Strands in Language Development Abstraction, Stepwise Refinement and Modules Structured Programming Standardisation Ada.. Modula Modula 2 Other Language Developments Logo.... Postscript, TeX and LaTeX Prolog SQL ICON.... Object Orientated Programming - OOP Oberon and Oberon Smalltalk

10 C++ Fortran 90 The Future and Further Sources Fortran High Perfonnance Fortran - HPF Network Sources Summary Bibliography. 7 Introduction to Programming. 7.1 Elements of a programming language 7.2 Variables - name, type and value 7.3 Notes 7.4 Some more Fortran rules 7.5 Good Programming Guidelines 7.6 Fortran Character set Notes Problems. 8 Introduction to Arithmetic 8.1 Rounding and truncation. 8.2 Example 1: Time taken for light to travel from the Sun to Earth The PARAMETER statement. Precision and size of numbers 8.5 Health Warning: Optional Reading, Beginners are Advised to Leave until Later Selecting different INTEGER Kinds Selecting different REAL Kinds Specifying Kind Types for Literal Integer and Real Constants Positional Number Systems... Bit Data Type and Representation Model.. Integer Data Type and Representation Model Real Data Type and Representation Model IEEE Example 2: Testing the numerical representation of different kind types on a system Example 3: Binary Representation of Different Integer Kind Type Numbers Summary of how to select the appropriate KIND type Summary Problems Bibliography 80 9 Arrays 1: Some Fundamentals Tables of data

11 9.1.1 Telephone directory Book catalogue Examination marks or results Monthly rainfall 9.2 Arrays in Fortran 9.3 The DIMENSION Attribute 9 A An index Control structure 9.6 Monthly Rainfall Example 1: Rainfall 9.7 People's Weights Example 2: People's Weights 9.8 Summary Problems Arrays 2: Further Examples 10.1 Higher dimension arrays Example 1: A Map Example 2: Booking arrangements in a theatre or cinema Additional forms of the DIMENSION attribute and DO loop statement Example 3: Voltage from -20 to +20 volts Example 4: Longitude from -180 to Notes The DO loop and straight repetition Example 5: Table of Temperatures Example 6: Means and Standard Deviations loa Summary Problems Arrays 3: Further Examples 11.1 Terminology Rank Bounds Extent Size Shape Conformable 11.2 Whole array manipulation Assignment Expressions Array Sections Example 1: Ages

12 Example 2: Examination Results Allocatable Arrays Example 3: Height Above Sea Level 11.5 Array Element Ordering Array Element Ordering and Physical and Virtual Memory 11.6 Array Constructors Masked Array Assignment and the WHERE Statement Notes Summary 11.9 Problems Output Integers, I format 12.2 Rea1s, F format 12.3 Rea1s, E format Spaces 12.5 Alphanumeric or character format, A 12.6 Common mistakes OPEN (and CLOSE) The OPEN statement Writing Repetition Some more examples Implied DO loops Formatting for a line-printer Mechanics of carriage control : 11.2 Generating a new line, on both line-printers and terminals Summary Problems Reading in Data Fixed fields on input Integers, the I format Reals, the F and E formats 13.2 Blanks, nulls and zeros 13.3 Characters Skipping spaces and lines 13.5 Reading File manipulation again 13.7 Errors when reading 13.8 Summary

13 13.9 Problems. 14 Functions An Introduction to Predefined Functions and Their Use l l Example I: Simple function usage Generic Functions Example 2: The ABS Generic function Elemental Functions Example 3: Elemental Function Use. Transformational Functions. Example 4: Simple Transformational Use Example 5: Intrinsic DOT]RODUCT use Notes on Function Usage. Example 6: Easter. Complete List of Predefined Functions Inquiry Functions Transfer and Conversion Functions Computational Functions Array Functions.... Pre-Defined Subroutines Supplying your own functions Example 7: Simple User Defined Function An Introduction to the Scope of Variables and Local Variables Recursive Functions Example 8: Recursive Factorial Evaluation Example 9: Recursive version of GCD Example 10: After Removing Recursion. Internal functions Example 11: Stirling's Approximation Resume Function Syntax Rules and Restrictions Problems Bibliography Recursion and Problem Solving 15 Control Structures Selection between courses of action The BLOCK IF statement Example 1: Quadratic Roots Note Example 2: Date calculation

14 The CASE Statement Example 3: Simple calculator Example 4: Counting Vowels, Consonants, etc The three forms of the DO statement.. Example 5: Sentinel Usage. CYCLE and EXIT Example 6: e**x Evaluation Example 7: Wave Breaking on an Offshore Reef 15.3 Summary Problems Bibliography 16 Character Character Input Character Operators 16.3 Character Sub-Strings 16.4 Character functions 16.5 Summary 16.6 Problems 17 Complex 17.1 Example 17.2 Complex and Kind Type 17.3 Summary 17.4 Problems 18 Logical I/O Summary 18.3 Problems 19 User Defined Types 19.1 Example 1 - Dates 19.2 Type Definition Variable Definition 19.4 Example 2 - Address lists 19.5 Example 3: Nested User Defined Types 19.6 Problems Bibliography Dynamic Data Structures 20.1 Example 1: Simple Pointer Concepts 20.2 Example 2: Singly linked list

15 20.3 Other Dynamic Data Structures Trees Example 3: Perfectly Balanced Tree 20.5 Using Linked Lists for Sparse Matrix Problems Inner Product of two Sparse Vectors Data Structures Summary 20.7 Problems Bibliography.. 21 Files 21.1 Files in Fortran Summary of options on OPEN 21.3 More fool proof i/o 21.4 Summary Problems An Introduction to Subroutines 22.1 Simple Subroutine Example 22.2 Defining a subroutine Referencing a subroutine Dummy Arguments or Parameters, and Actual Arguments 22.5 Interface 22.6 Intent 22.7 Local Variables Local Variables and the SAVE attribute 22.8 Scope of Variables Status of the Action Carried out in the Subroutine Why Bother? Summary Problems. 23 Subroutines: Example 1: Introduction to Arrays as Parameters Explicit Shape Dummy Arrays Example 2: Characters as parameters and assumed length dummy arguments 23.3 Example 3: Using Hoare's Quick Sort Algorithm Note 2 - Intent Attribute Note 3 - Explicit shape dummy array Note 4 - Assumed Length Dummy Argument Note 5 - Recursive Subroutine Note 6 - Internal Subroutines and Scope Note 7 - Flexible Design

16 23.4 Example 4: Rank two and higher arrays as parameters Assumed Shape Arrays Summary Problems Bibliography An Introduction to Modules 24.1 Modules for global data Example 1: Modules for Precision Specification and Constant Definition Note Example 2: Constant Definition and Array Definition 24.2 Modules for derived data types Example 3: Person Data Type Modules for explicit procedures interfaces Example: Using QuickSort Modules containing procedures Example 4 - The Solution of Linear Equations Using Gaussian Elimination Notes Notes on Module Usage and Compilation 24.7 Summary Problems Bibliography Formal Syntax and Some Additional Features 25.1 Program Units Procedure - Function or Subroutine Internal Procedure Module..... Executable Statements. Statement Ordering Entities... Scope and Association Modules and Scope Public and Private Attributes USE, ONLY and Rename. Keyword and Optional Arguments. Syntax Summary of Some Frequently used Fortran Constructs Main Program Subprogram... Module.... Internal Procedure

17 l l l O.l2 25.l0.13 Procedure heading Procedure ending. Specification construct Derived Type definition Interface block... Specification statement Type specification Attribute Specification Executable construct Action statement Case Studies Example 1 - Solving a System of First Order Ordinary Differential Equations using Runge-Kutta-Merson Note: Alternative fonn of the Allocate statement Note: Automatic arrays Note: Dummy Procedure Arguments Example 2 - Generic Procedures Example 3 - A Function that returns a variable length array Example 4 - Operator and Assignment Overloading Example 5: A Subroutine to Extract the Diagonal Elements of a Matrix Modules and Packaging Problems Bibliography Converting from Fortran Deleted Features Obsolescent Features l Arithmetic IF Real and Double precision DO Control Variables Shared DO tennination and non ENDDO tennination Alternate RETURN PAUSE Statement ASSIGN and assigned GOTO statements Assigned FORMAT statements H Editing Better Alternatives Miscellanea Program Development and Software Engineering Modules Programming Style - Programs should be Easy to Read Programming Style - Programs should Behave Well

18 28.2 Data Structures 28.3 Algorithms 28.4 Recursion Structured Programming and the GOTO Statement 28.6 Efficiency, space time trade off Program Testing Simple Debugging Techniques 28.9 Software Tools Cross Referencing Pretty print NAGWare f90 Tools Numerical Software Sources Coda Bibliography: All sources (bar one) taken from comp.software-eng Software Engineering Programming Style Software Testing Fun... Glossary Appendix A, Sample Program Examples Appendix B, ASCII Character Set.. Appendix C, Intrinsic Functions and Procedures Appendix D, English and Latin Texts Appendix E, Coded Text Extracts.... Appendix F, NAG.... Appendix G, Annex D, ISO/IEC 1539: 1991 (E) Index

Introduction to Programming with Fortran

Introduction to Programming with Fortran Ian D. Chivers and Jane Sleightholme Introduction to Programming with Fortran With Coverage of Fortran 90, 95, 2003, and 77 Ian D. Chivers, BSc, PGCEd, MSc, MBCS