EPSILON (real)

  Class:  Inquiry function - Generic

  Returns a positive model number that is almost negligible compared
  to unity in the model representing real numbers.  The argument can
  be scalar or array valued.

  The model for real numbers is described in the HP Fortran for
  OpenVMS Language Reference Manual.

  Example:

  If X is REAL*4 type, EPSILON (X) has the value 2**-23.