fortran select case

In Fortran, the SELECT CASE construct is used to perform different actions based on the value of an expression. It is similar to the switch statement in other programming languages.

Here is the basic syntax of the SELECT CASE construct in Fortran:

SELECT CASE (expression)
  CASE (value1)
    ! statements executed when expression equals value1
  CASE (value2)
    ! statements executed when expression equals value2
  CASE (value3)
    ! statements executed when expression equals value3
    ! statements executed when none of the above cases match

The expression can be any scalar expression, such as a variable, a constant, or an arithmetic expression.

The CASE statement is used to define specific values that the expression can take. When the expression matches one of the CASE values, the corresponding block of statements is executed. If none of the CASE values match the expression, the statements under the CASE DEFAULT block are executed.

Here's an example to illustrate the usage of SELECT CASE in Fortran:

PROGRAM SelectCaseExample
  INTEGER :: num

  WRITE(,) "Enter a number:"
  READ(,) num

    CASE (0)
      WRITE(,) "The number is zero."
    CASE (1)
      WRITE(,) "The number is one."
    CASE (2, 3, 4)
      WRITE(,) "The number is two, three, or four."
      WRITE(,) "The number is not zero, one, two, three, or four."

END PROGRAM SelectCaseExample

In this example, the user is prompted to enter a number. Based on the value entered, the program uses a SELECT CASE construct to determine which block of statements to execute.

I hope this explanation helps you understand how to use the SELECT CASE construct in Fortran. If you have any further questions, feel free to ask.