PROBLEM SOLVING WITH FORTRAN 90

Transcription

1 David R. Brooks PROBLEM SOLVING WITH FORTRAN 90 FOR SCIENTISTS AND ENGINEERS Springer

2 Contents Preface v 1.1 Overview for Instructors v The Case for Fortran 90 vi Structure of the Text vii Introductory Material vii Presentation of the Language ix i. 1.3 Decisions About Content ix Program Layout x Data Types x Derived Data Types xi Pointers and Allocatable Arrays xi Recursion xii Explicit vs. Implicit Typing xiii COMMON Blocks xiii Program Modularization xiv Arrays xiv Pedagogical Features xv A Formal Problem-Solving Process Is Followed Throughout the Text xv Some Applications and Problems Appear More Than Once xv Programs and Exercises xvi The Compiler Used to Prepare Programs for This Text... xvii 1.2 Overview for Students xviii The Purpose of This Text xviii The Approach Taken by the Text xviii What Does This Textbook Expect from You xx and What Does It Offer in Return? xxi 1.3 Useful References for Fortran 90 xxii 1.4 Contacting the Author xxii 1.5 Obtaining Source Code and Data Files for Programs in this Text xxii 1.6 Acknowledgments xxiii 1. Computing Environments for Problem Solving A Brief History of Electronic Computing The First Generation The Second and Third Generations The Fourth Generation 3

3 xxvi Contents 1.2 The Academic Computing Environment The Department-Based Computing Environment The Personal Computing Environment What Do You Need to Know About Your Computing Environment? Fortran and the Personal Computing Environment Is Programming Necessary Anymore? Exercises Solving Problems with a High-Level Programming Language Structured Programming and Problem Solving A High-Level Programming Language Provides the Tool Developing a Formal Approach to Problem Solving Beware of Logical Errors Designing Algorithms for Procedural Programming Languages Getting Started Executable Instructions Data Types and Variables 37 Data types 37 Variables Designing Algorithms for Solving Problems 40 Defining a pseudocode language 40 The three basic program control structures 44 Adding to your pseudocode vocabulary 45 Flowcharts: another way to visualize algorithms Program Modularization Applications Maximum Deflection of a Beam Under Load Oscillating Frequency of an LC Circuit Debugging Your Algorithms Algorithm Style Problems with Your Algorithms Exercises Self-Testing Exercises Basic Algorithm Development Exercises Algorithm Development Applications Getting Started with Fortran: Writing Simple Programs A Simple Problem and a Fortran Program to Solve It Program Layout What Is "Source Code?" Where Does Source Code Come From? Why Do the Fortran Statements All Start in Column 7?... 77

4 Contents xxvii Inserting Comments in Source Code Files How Much of P-3.1 Is Absolutely Necessary and How Much Is a Matter of Style? Fortran Keywords What If a Statement Is Too Long to Fit on a Single Line? Executable and Nonexecutable Statements Declaring Variables and Defining Constants Variable Names and Data Type Declarations Intrinsic Data Types 85 Type declarations for intrinsic data types 85 Type declarations for numbers 86 Type declarations for logical variables 87 Type declarations for characters and strings of characters 88 The PARAMETER attribute and statement 89 Enforcing explicit typing 90 The implications of type declaration 91 Using nonexecutable statements in programs Constants 92 Integers and real numbers 92 Logical constants 93 Character constants Initializing Values with the DATA Statement List-Directed Input and Output Reading and Displaying Numerical Values 96 Displaying a prompt for user input 96 Getting input from the keyboard 97 Displaying output Manipulating Text Information Arithmetic Operators, Assignment Statements, and Calculations Arithmetic Operators, Expressions, and the Assignment Operator Assignment Statements That Increment Variables Mixed-Mode Calculations Using Compatible Constants Operator Precedence Program Termination Compiling and Executing a Program Source Code Portability Compilation and Execution Saving Output from Your Programs 121

5 xxviii Contents 3.8 Applications Maximum Deflection of a Beam Under Load Relativistic Mass and Speed of an Electron Debugging Your Programs Programming Style Your Programs Will Often Contain Errors Some Common Errors 129 Compilation Errors 130 Execution Errors 130 Logical Errors Forcing Your Programs to Fail Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Using Functions to Expand the Power of Fortran Fortran Intrinsic Functions Intrinsic Functions for Arithmetic Calculations: Arguments and Ranges Intrinsic Functions for Character and String Manipulation Examples of Calculations Using Intrinsic Functions 157 Polar/Cartesian conversions 157 Calculating the absolute value 161 The remainder from integer or real division Fortran Statement Functions Applications Refraction of Light Inverse Hyperbolic Functions Debugging Your Programs Programming Style Problems with Programs Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Gaining Control Over Program Output The Formatted PRINT Statement Introduction to Formatted Output 187

6 Contents xxix Format Descriptors for Numbers and Character Strings INTEGER descriptors 190 REAL descriptors 190 CHARACTER descriptors 193 LOGICAL descriptor 193 General descriptor 193 String constant descriptors Control Descriptors 193 Carriage control 193 Skipping spaces 194 Sign display 194 New lines 195 Tabulation 195 Format termination Repeating Groups of Descriptors Producing Formatted Output Without a FORMAT Statement The WRITE Statement Syntax of the WRITE Statement and the Standard Output Unit Format Descriptors for the WRITE Statement Saving Program Output Applications Stellar Magnitude and Distance Relativistic Mass and Speed of an Electron Debugging Your Programs Programming Style Problems with Programs Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Program Control: Branching and Repetitive Calculations Using Program Control Structures The IF...THEN...(ELSE...) Pseudocode Construct The CHOOSE Pseudocode Command The LOOP...END LOOP Pseudocode Command 219 Count-controlled loops 219 Conditional loops Relational and Logical Operators and the Fortran IF... Construct 222

7 xxx Contents Relational and Logical Operators The IF... Construct Using the IF... Construct in Programs The SELECT CASE Construct Fortran Loop Constructs Count-Controlled (DO...) Loops Pre- and Post-Test Conditional Loop Constructs 241 Pre-test loops 241 Post-test loops Nested Loops Loop Design Considerations Using Implied DO... Loops in Output Statements Applications Refraction of Light Oscillating Frequency of an LC Circuit Calculating Radiation Exposures for a Materials Testing Experiment Maximum Deflection of a Beam with Various Support/Loading Systems Debugging Your Programs Programming Style Logical Problems Syntax and Execution Problems Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Program Modularization Designing Modularized Algorithms with the CALL and SUBPROGRAM Pseudocode Commands Fortran Subroutines Using Subroutines Controlling the Flow of Information 289 Expressing intent 289 Enforcing intent More About SUBROUTINE Syntax Fortran Functions Using Subroutines and Functions Using the MODULE Structure for Passing Information to Subroutines and Functions Initializing Information in Subroutines and Functions

8 Contents xxxi Using Subroutines and Functions in Argument and Parameter Lists Choosing Between Subroutines and Functions Applications Relativistic Mass and Speed of an Electron A Function Library for Converting Units A Simple Character-Based Function Plotter Debugging Your Programs Programming Style Problems with Programs Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Using Arrays to Organize Information Arrays in Structured Programming Basic Array Implementation Example: Testing a Random Number Generator Declaring Arrays Assigning Values to Arrays 342 Assigning a value to an entire array or part of an array Assigning array elements with count-controlled loops Assigning values to individual array elements 344 Using a DATA statement to initialize arrays 345 Using elemental intrinsic functions Displaying the Contents of Arrays (Implied DO... Loops) Example: Monthly Ozone Summary Using Statically Allocated Arrays in Subprograms Allocatable Arrays Treating Strings of Characters as Arrays of Characters The TYPE Statement, Records, and Arrays of Records Applications Vector Operations Cellular Automata and Sierpinski Triangles Probability Analysis for Quality Control of Manufacturing Processes Debugging Your Programs Programming Style Problems with Programs That Use Arrays Exercises Self-Testing Exercises 391

9 xxxii Contents Basic Programming Exercises Programming Applications Using Formatted Sequential Access and Internal Files The Text File Concept OPEN, READ, and CLOSE Statements for Sequential File Access Reading a File Containing Student Names and Grades The OPEN and REWIND Statements The READ and BACKSPACE Statements The CLOSE Statement Files and Arrays More About Formatted READ Statements FORMAT Statements and Standard Field Descriptors Reading Internal Files Writing Text Files Applications Exponential Smoothing of Data Billing Program for an Urban Water Utility Merging Sorted Lists Creating a "Quote-and-Comma-Delimited" Input File for Spreadsheets Debugging Your Programs Programming Style Problems with Programs That Access External Data Files Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Some Essential Programming Algorithms Introduction Searching Algorithms Linear Searches Binary Search Comparing Searching Algorithms A Driver Program for Testing Searching Algorithms Sorting Algorithms Selection Sort Insertion Sort Efficiency of Sorting Algorithms A Driver Program for Testing Sorting Algorithms Recursive Algorithms The Recursive Quicksort Algorithm 501

10 Contents xxxiii 10.6 Applications Keeping a List of Words in Alphabetical Order Evaluating Legendre Polynomials Debugging Your Programs Programming Style Problems with Programs Exercises Self-Testing Exercises Basic Programming Exercises Programming Applications Basic Statistics and Numerical Analysis with Fortran Introduction Basic Descriptive Statistics The Sample Mean and Standard Deviation Linear Regression and the Linear Correlation Coefficient Numerical Differentiation Newton's and Stirling's Formulas Application. Estimating the Speed of a Falling Object Numerical Integration Polynomial Approximation Methods Application: Evaluating the Gamma Function Solving Systems of Linear Equations Linear Equations and Gaussian Elimination Application: Current Row in a DC Circuit with Multiple Resistive Branches Finding the Roots of Equations Numerical Solutions to Differential Equations Motion of a Damped Mass and Spring Application. Current Flow in a Series LRC Circuit Exercises Basic Programming Exercises Programming Applications A Closer Look Introduction Using More Than One Program Unit Merging Source Code Merging Object Code 602

11 xxxiv Contents 12.3 The Internal Representation of Numbers and Extended Precision Internal Representation of Numbers 604 Integers 604 Real Numbers Specifying Precision for Numerical Variables Array Operations and Array Inquiry and Reduction Intrinsic Array Operations Array Functions 614 Array multiplication functions 616 Array inquiry functions 616 Array reduction functions Direct Access and Unformatted (Binary) Files Introduction to File Types Using Other File Types Example: Binary Search of a File The COMPLEX Data Type Data Sharing With COMMON Blocks 636 Appendices 641 Appendix 1. Table of ASCII Characters for IBM-Compatible PCs Appendix 2. Summary of Pseudocode Commands and Fortran Statement Syntax 643 Appendix 2.1 Pseudocode Commands 643 Appendix 2.2 Fortran Statement Syntax 644 Appendix 3. Source Code File Name Summary 655 Appendix 4. Accessing the System Time and Date 661 Glossary 661 Index 673