! Plotting grogram for general purpose using PostScript
  program main
    call init
      call viewport(0.2, 0.2, 0.8, 0.6)
      call xyworld (0.0, -1.0, 1.0, 1.0)
      call frame
      call plotd
      call fin
   stop
   end
!
  function f(x) 
   real(4) :: pi, f, x
   pi=atan(1.0)*4.0
   f=exp(-x)*sin(4.0*pi*x)
  return
  end 
  subroutine plotd()
   REAL(4) :: x1(0:20),y1(0:20)
   INTEGER :: i,n=20
     do i=0,n
      x1(i)=float(i)/float(n)
      y1(i)=f(x1(i))
     end do
     call linewidth(1.5)
     call linety(1)
     call setgray(0.0)
     call plot(x1(0), y1(0), 3)
     do i=1, n-2
       call spline1( x1(i-1), y1(i-1), x1(i), y1(i), x1(i+1), y1(i+1), & 
                     x1(i+2), y1(i+2), -1)
     end do
     call spline1( x1(n-3), y1(n-3), x1(n-2), y1(n-2), x1(n-1), y1(n-1), & 
                     x1(n), y1(n), 0)
     call spline1( x1(n-3), y1(n-3), x1(n-2), y1(n-2), x1(n-1), y1(n-1), & 
                     x1(n), y1(n), 1)
     call stroke()
    return
    end
    subroutine frame
      REAL(4) :: x,y,dx,dy 
      INTEGER :: nx,ny,ix,iy
      call linewidth(1.0)
      call rect(0.0, -1.0, 1.0, 1.0, 0.0, 1.0, 1)
      nx=2
      do ix = 1, nx*10-1
         x = float(ix)/float(nx*10)
         dy=1.0
         if(ix/10*10.eq.ix) then
            call setgray(0.5)
           else
            call setgray(0.8)
         end if
         call  plot( x, -dy, 3)
         call  plot( x, dy, 2)
         call stroke()
      end do
      ny=2
      do iy = 1, ny*10-1
         y = float(iy)/float(ny*10)*2.0-1.0
         dx=1.0
         if(iy/10*10.eq.iy) then
            call setgray(0.5)
           else
            call setgray(0.8)
         end if
         call  plot( 0.0, y, 3)
         call  plot( dx,  y, 2)
         call stroke()
      end do
      call setgray(0.0)
      call textx(0.75, 0.0, 1, 'x')
      call textx(0.05, 0.02, 1, '0')
      call textx(0.55, 0.02, 3, '0.5')
      call textx(0.95, 0.02, 1, '1')
      call texty(0.0, 0.5, 1, 'y')
      call texty(0.0, -1.0, 2, '-1')
      call texty(0.0, 0.0, 1, '0')
      call texty(0.0, 1.0, 1, '1')
   return
   end