implicit real(a-h,o-z)
      real func, a, b, h, s, t, sumo, sume
      parameter(a=0.0, b=2.0)
      real*8 ffunc, aa, bb, hh, ss, tt, ssumo, ssume, pi
      parameter(aa=0.0d0, bb=2.0d0)
      integer m
      func(t) = sqrt(4.0-t**2)
      ffunc(tt) = sqrt(4.0d0-tt**2)
c
      pi = atan(1.0d0)*4.0d0
c
      write(6,'(3x,a,7x,a,9x,a,7x,a,2x,a)')
     $    'Num.', 'Single','Double','Single-Double','Single-Exact'
      do j = 1, 20
         m = 2**j
c
         h = (b-a)/m
         sumo = 0.0
         sume = 0.0
c
         do i = 1 , m/2-1
            sumo = sumo + func(a+h*(2*i-1))
            sume = sume + func(a+h*(2*i))
         end do
         sumo = sumo + func(b-h)
         s = ( func(a) + func(b) + 4.0*sumo + 2.0*sume )*h/3.0
c
         hh = (bb-aa)/m
         ssumo = 0.0d0
         ssume = 0.0d0
c
         do i = 1 , m/2-1
            ssumo = ssumo + ffunc(aa+hh*(2*i-1))
            ssume = ssume + ffunc(aa+hh*(2*i))
         end do
         ssumo = ssumo + ffunc(bb-hh)
         ss = ( ffunc(a) + ffunc(b) + 4.0d0*ssumo + 2.0d0*ssume )*hh
     $       /3.0d0
c
         write(6,'(i8,f15.7,f15.7,f15.7,f15.7)')
     $    m, s, ss, s-ss, s-pi
      end do
c
      end