anchor.diff:  
     end subroutine write_critical_points
   
  -
  -  !-------------------------------------------------------------------------
  -  ! Subroutine to save in a file two sets of data
  -  !-------------------------------------------------------------------------
  -  subroutine save_data(fid, filename, n, length, data_1, data_2, data_3)
  -    implicit none
  -
  -    integer                                  ,intent(in):: fid
  -    character(len =64)                       ,intent(in):: filename
  -    integer                                  ,intent(in):: n
  -    real(kind = x_precision)                 ,intent(in):: data_1
  -    real(kind = x_precision)                 ,intent(in):: data_2
  -    real(kind = x_precision)                 ,intent(in):: data_3
  -
  -    integer                               ,intent(inout):: length
  -
  -    !------------------------------------------------------------------------
  -
  -    if( length .eq. 1 ) then
  -       open(fid,file  = filename, action='readwrite')
  -       write(fid,'(3(A16))') 'Surface_density', 'Temperature', 'Optical_depth'
  -    end if
  -
  -    write(fid,'(3(e16.6e2))') data_1, data_2, data_3
  -
  -    if( length .eq. n ) then
  -       close(fid)
  -    end if
  -
  -  end subroutine save_data
   
   
     !-------------------------------------------------------------------------
  
positive.code:     character(len = 64)                                    :: fname_tot
      integer                                                :: fid_tot
      integer                                                :: ios
   ! For the critical points
      integer                                                :: index_fcp
      real(kind = x_precision)                               :: sigma_c_thick
  
negative.code:       ! ADIMENSIONED critical T and S [OUTPUT]
  
        temperature(k) = temp_c_thick
        s(k)           = sigma_c_thick 
  
        ! DIMENSIONED critical T and S
        temp_thick(k)  =  temp_c_thick * state_0%T_0
  