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Selections (IF, IF-ELSE, CASE)

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• Types of selection statements
  • Two-way selection statements: IF, IF-ELSE

  • Multiway selection statements: CASE

  • NOTE:

    Although F90 accepts F77 syntax, I will focus on the F90/F95 forms

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• IF-statement
  • Syntax:

    IF ( condition ) THEN one or more statments END IF

    Example:

    if ( i < j ) then print *, "i < j" end if if ( i > j ) then print *, "i > j" end if if ( i == j ) then print *, "i == j" end if

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  • Example Program: (Demo above code)                                                
    • Prog file: click here

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• IF-ELSE-statement
  • Syntax

    IF ( condition ) THEN one or more statments ELSE one or more statments END IF

    Example:

    integer grade print *, "Enter grade value = " read *, grade if ( grade >= 90 ) then print * print *, "Letter grade is A" else if ( grade >= 80 ) then print * print *, "Letter grade is B" else if ( grade >= 70 ) then print * print *, "Letter grade is C" else if ( grade >= 60 ) then print * print *, "Letter grade is D" else print * print *, "Letter grade is F" end if

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  • Example Program: (Demo above code)                                                
    • Prog file: click here

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• CASE-statement
  • Syntax:

    SELECT CASE ( variable ) CASE (constants1, constants2) ! List of constants multiple statments CASE (const3:const4) ! Ranges multiple statments CASE (constants5, const6:const7) ! Even mixture... multiple statments [CASE DEFAULT multiple statments] END SELECT

    Example:

    integer grade select case (grade) case (90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100) print * print *, "Letter grade is A" case (80:85, 87:89) print * print *, "Letter grade is B" case (70:79) print * print *, "Letter grade is C" case (60:69) print * print *, "Letter grade is D" case default print * print *, "Letter grade is F" end select

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  • Example Program: (Demo above code)                                                
    • Prog file: click here