Programming Fundamentals/Loops/Fortran

loops.f90

! This program demonstrates While, Do, and For loop counting using
! user-designated start, stop, and increment values.
!
! References:
!   https://www.tutorialspoint.com/fortran
!   https://en.wikibooks.org/wiki/Fortran

! This program asks the user to select Fahrenheit or Celsius conversion
! and input a given temperature. Then the program converts the given 
! temperature and displays the result.

! References:
!   https://www.tutorialspoint.com/fortran
!   https://en.wikibooks.org/wiki/Fortran

program loops
    integer :: get_value
    integer :: start, stop, increment

    start = get_value("starting")
    stop = get_value("ending")
    increment = get_value("increment")

    call while_loop(start, stop, increment)
    call do_loop(start, stop, increment)
    call for_loop(start, stop, increment)
end program

function get_value(label) result (value)
    character(*) :: label
    integer :: value

    print ("(a a a)"), "Enter ", label, " value:"
    read *, value
end function

subroutine while_loop(start, stop, increment)
    integer :: start, stop, increment
    integer :: count
    
    print ("(/ a i2 a i2 a i2 a)"), &
        "While loop counting from ", start, &
        " to ", stop, " by ", increment, ":"
    count = start
    do while (count <= stop)
        print ("(i2)"), count
        count = count + increment
   end do
end subroutine

subroutine do_loop(start, stop, increment)
    integer :: start, stop, increment
    integer :: count
    
    print ("(/ a i2 a i2 a i2 a)"), &
        "Do loop counting from ", start, &
        " to ", stop, " by ", increment, ":"
    count = start
    do
        print ("(i2)"), count
        count = count + increment
        if (.not. count <= stop) then
            exit
        end if
   end do
end subroutine

subroutine for_loop(start, stop, increment)
    integer :: start, stop, increment
    integer :: count
    
    print ("(/ a i2 a i2 a i2 a)"), &
        "For loop counting from ", start, &
        " to ", stop, " by ", increment, ":"
    do count = start, stop, increment
        print ("(i2)"), count
   end do
end subroutine

Try It

Copy and paste the code above into one of the following free online development environments or use your own Fortran compiler / interpreter / IDE.

• CodeChef
• GDB Online
• Ideone
• RexTester
• TutorialsPoint

See Also

• TutorialsPoint: Fortran
• Fortran90.org: Best Practices

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