4Numbers of type real have approximately seven signiο¬cant digits. The accuracy of the
  operations described above is determined by the number 
, which is the smallest positive
  number such that 
. For a variable x of some type, this number is given by a call to the
  Fortran intrinsic function epsilon(x). For variables of type real, 
 and for
  variables of type real(8) 
.