E_VERSUS_D:
  FORTRAN90 version.
  Demonstrating that FORTRAN constants are single precision
  by default, no matter how many digits you type.
  The only cure is to use the "D" exponent marker.

TEST01

  X1 and X2 are both double precision variables.

  We initialize them with almost identical statements:

    x1 = 1.2345678901234567890E+00
    x2 = 1.2345678901234567890D+00

  But X1 and X2 do not receive the same values, which we can
  verify by printing them, or by computing their difference.

  X1           =      1.2345678806304931641    
  X2           =      1.2345678901234566904    
  X3 = X1 - X2 =    -0.94929635263696354741E-08

E_VERSUS_D:
  Normal end of execution.