! Example P.2. (Catherine Spade, 4 October 1999)
! Examples of intrinsic library functions.
  program A02
    implicit none
    real :: A
    real, parameter :: B = 1.234, C = 5.678
    integer, parameter :: I = 9, J = 10
! start program A02
    A = sqrt( B ) + abs( C )
    write (unit = *, fmt = *) A, int( A ), nint( A ), real( I ), I
    write (unit = *, fmt = *) I / J, modulo( I, J ), abs( I ), sign( I, 1 ), sign( I, -1 )
    write (unit = *, fmt = *) B, B / C, modulo( B, C ), abs( B )
    write (unit = *, fmt = *) sign( B, 1.0 ), sign( B, -1.0 )
    write (unit = *, fmt = *) atan2( 0.0, -1.0 ), exp( 1.0 )
    write (unit = *, fmt = *) cos( 1.0 ), sin( 1.0 ), tan( 1.0 ), log( 2.0 ), log10( 2.0 )
    stop
  end program A02

! Example P.4. Prompting for terminal keyboard input.
  program A04
    implicit none
    real :: X, Y, Average, Diameter, Fahr, Cels
    real, parameter :: T_SCALE = 1.8, OFFSET = 32.0
! start program A04
    write (unit = *, fmt = *) " Please enter two numbers to be averaged. "
    read (unit = *, fmt = *) X, Y
    Average = (X + Y) / 2.0
    write (unit = *, fmt = *) " The average of ", X, " and ", Y, " is: ", Average
    write (unit = *, fmt = *) " Please enter the diameter of a circle. "
    read (unit = *, fmt = *) Diameter
    write (unit = *, fmt = *) " Circumference: ", atan2( 0.0, -1.0 ) * Diameter
    write (unit = *, fmt = *) " Please enter the Fahrenheit temperature. "
    read (unit = *, fmt = *) Fahr
    Cels = (Fahr - OFFSET) / T_SCALE
    write (unit = *, fmt = *) Fahr, " deg. F = ", Cels, " deg. C "
    stop
  end program A04

! Example P.5. (Catherine Spade, 8 October 1999)
! Temperature Converter with Repetition.
  program A05
    implicit none
    integer, parameter :: LIMIT = 10
    real, parameter :: T_SCALE = 1.8, OFFSET = 32.0
    real :: Fahr, Cels
    integer :: Loop
! start program A05
    do Loop = 1, LIMIT
      write (unit = *, fmt = *) " Please enter Fahrenheit temperature ", Loop, ":"
      read (unit = *, fmt = *) Fahr
      Cels = (Fahr - OFFSET) / T_SCALE
      write (unit = *, fmt = *) Fahr, Cels
    end do
    stop
  end program A05

! Count high and low temperatures.
  program A06
    implicit none
    integer, parameter :: LIMIT = 30
    real, parameter :: BOUNDARY = 68.0
    real :: Temperature
    integer :: High_Count, Low_Count, Loop
! start program A06
    High_Count = 0
    Low_Count = 0
    do Loop = 1, LIMIT
      write (unit = *, fmt = *) " Please enter the next temperature. "
      read (unit = *, fmt = *) Temperature
      if (Temperature >= BOUNDARY) then
        High_Count = High_Count + 1
      else
        Low_Count = Low_Count + 1
      end if
    end do
    write (unit = *, fmt = *) High_Count, " hot days, and ", Low_Count, " cold days this month."
    stop
  end program A06

! Temperature Converter with Procedures.
  program A08
    use A08M
    implicit none
    real :: Fahr, Cels
! start program A08
    call Input( Fahr ) ! Subroutine reference
    Cels = Temp_C( Fahr )  ! Function reference
    call Output( Fahr, Cels )  ! Subroutine reference
    stop
  end program A08

  module A08M
    implicit none
    public :: Input, Temp_C, Output
  contains
    subroutine Input( F_Temp )
      real, intent(out) :: F_Temp
  ! start subroutine Input
      write (unit = *, fmt = *) " Please enter the Fahrenheit temperature. "
      read (unit = *, fmt = *) F_Temp
      return
    end subroutine Input
    function Temp_C( F_Temp ) result( Temp_C_R )
      real, intent(in) :: F_Temp
      real :: Temp_C_R
    real, parameter :: T_SCALE = 1.8, OFFSET = 32.0
  ! start function Output
      Temp_C_R = (F_Temp - OFFSET) / T_SCALE
      return
    end function Temp_C
    subroutine Output( F_Temp, Temp_C_R )
      real, intent(in) :: F_Temp, Temp_C_R
  ! start subroutine Output
      write (unit = *, fmt = *) F_Temp, " deg. F = ", Temp_C_R, " deg. C"
      return
    end subroutine Output
  end module A08MTally( )