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Fortran (short for "Formula Translation") is one of the oldest high-level programming languages and is particularly well-suited for numerical and scientific computing. OpenVMS provides robust support for Fortran, allowing developers to leverage the language's capabilities on this powerful operating system.

Overview

In this section, we will cover:

Introduction to Fortran on OpenVMS
Setting up the Fortran environment
Writing and compiling Fortran programs
Debugging Fortran programs
Practical exercises

Introduction to Fortran on OpenVMS

Fortran has evolved significantly since its inception, with modern versions supporting advanced features such as modular programming, array operations, and parallel computing. OpenVMS supports various versions of Fortran, including Fortran 77, Fortran 90, and later standards.

Key Features of Fortran on OpenVMS:

High Performance: Optimized for numerical and scientific computations.
Compatibility: Supports legacy Fortran code while providing modern features.
Integration: Seamlessly integrates with OpenVMS system services and libraries.

Setting Up the Fortran Environment

Before you can start writing and compiling Fortran programs on OpenVMS, you need to ensure that the Fortran compiler is installed and properly configured.

Steps to Set Up the Fortran Environment:

Check for Fortran Compiler:
```
$ FORTRAN /VERSION
```
This command will display the version of the Fortran compiler installed on your system.
Set Up Environment Variables: Ensure that the necessary environment variables are set. Typically, this involves setting the FORTRAN logical name to point to the Fortran compiler.
```
$ DEFINE FORTRAN SYS$SYSTEM:FORTRAN.EXE
```
Verify Installation: Compile a simple Fortran program to verify that the compiler is working correctly.

Writing and Compiling Fortran Programs

Example Fortran Program:

Here is a simple Fortran program that calculates the sum of two numbers.

PROGRAM SumTwoNumbers
  IMPLICIT NONE
  INTEGER :: num1, num2, sum

  ! Prompt the user for input
  PRINT *, 'Enter first number:'
  READ *, num1
  PRINT *, 'Enter second number:'
  READ *, num2

  ! Calculate the sum
  sum = num1 + num2

  ! Display the result
  PRINT *, 'The sum of the two numbers is:', sum
END PROGRAM SumTwoNumbers

Compiling the Fortran Program:

To compile the above Fortran program, save it to a file named sum_two_numbers.f90 and use the following command:

$ FORTRAN sum_two_numbers.f90
$ LINK sum_two_numbers
$ RUN sum_two_numbers

Explanation:

FORTRAN sum_two_numbers.f90: Compiles the Fortran source code.
LINK sum_two_numbers: Links the compiled object file to create an executable.
RUN sum_two_numbers: Executes the compiled program.

Debugging Fortran Programs

Debugging is an essential part of the development process. OpenVMS provides tools to help you debug Fortran programs.

Using the OpenVMS Debugger:

Compile with Debug Information:

$ FORTRAN /DEBUG sum_two_numbers.f90
$ LINK /DEBUG sum_two_numbers

Run the Debugger:
```
$ DEBUG sum_two_numbers
```
Common Debugger Commands:
- SET BREAK: Set a breakpoint at a specific line.
```
DBG> SET BREAK sum_two_numbers.f90\10
```
- GO: Start or continue program execution.
```
DBG> GO
```
- EXAMINE: Examine the value of a variable.
```
DBG> EXAMINE sum
```

Practical Exercises

Exercise 1: Simple Arithmetic Operations

Write a Fortran program that performs addition, subtraction, multiplication, and division of two numbers provided by the user.

Solution:

PROGRAM ArithmeticOperations
  IMPLICIT NONE
  REAL :: num1, num2, sum, difference, product, quotient

  ! Prompt the user for input
  PRINT *, 'Enter first number:'
  READ *, num1
  PRINT *, 'Enter second number:'
  READ *, num2

  ! Perform arithmetic operations
  sum = num1 + num2
  difference = num1 - num2
  product = num1 * num2
  quotient = num1 / num2

  ! Display the results
  PRINT *, 'Sum:', sum
  PRINT *, 'Difference:', difference
  PRINT *, 'Product:', product
  PRINT *, 'Quotient:', quotient
END PROGRAM ArithmeticOperations

Exercise 2: Factorial Calculation

Write a Fortran program that calculates the factorial of a given number using a loop.

Solution:

PROGRAM Factorial
  IMPLICIT NONE
  INTEGER :: num, i, factorial

  ! Prompt the user for input
  PRINT *, 'Enter a number:'
  READ *, num

  ! Initialize factorial
  factorial = 1

  ! Calculate factorial using a loop
  DO i = 1, num
    factorial = factorial * i
  END DO

  ! Display the result
  PRINT *, 'Factorial of', num, 'is', factorial
END PROGRAM Factorial

Conclusion

In this section, we have covered the basics of using Fortran on OpenVMS, including setting up the environment, writing and compiling programs, and debugging. We also provided practical exercises to reinforce the concepts learned. With this foundation, you are now ready to explore more advanced Fortran programming techniques and integrate your Fortran applications with OpenVMS system services.

Using Fortran on OpenVMS

Overview

Introduction to Fortran on OpenVMS

Key Features of Fortran on OpenVMS:

Setting Up the Fortran Environment

Steps to Set Up the Fortran Environment:

Writing and Compiling Fortran Programs

Example Fortran Program:

Compiling the Fortran Program:

Explanation:

Debugging Fortran Programs

Using the OpenVMS Debugger:

Practical Exercises

Exercise 1: Simple Arithmetic Operations

Exercise 2: Factorial Calculation

Conclusion

OpenVMS Programming Course

Module 1: Introduction to OpenVMS

Module 2: Basic OpenVMS Commands

Module 3: OpenVMS File System

Module 4: Scripting with DCL

Module 5: OpenVMS System Management

Module 6: Networking on OpenVMS

Module 7: Advanced OpenVMS Programming

Module 8: OpenVMS Clustering

Module 9: OpenVMS Security

Module 10: Troubleshooting and Optimization