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
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Copy and paste the code above into one of the following free online development environments or use your own Fortran compiler / interpreter / IDE.
loops.f90

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See Also
