VMS Help PASCAL, Data Types, Real  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Real types specify real number values with different degrees  of
  precision.

1 - REAL

  The REAL type denotes single-precision real  values.   The  REAL
  type is synonymous with the SINGLE type.  The largest REAL value
  is denoted by MAXREAL.  The smallest REAL value  is  denoted  by
  MINREAL.  EPSREAL denotes the result of subtracting 1.0 from the
  smallest REAL value that is greater than 1.0.

  Example:  2.4
            2.3e2        {exponential notation}

  On OpenVMS VAX systems, REAL uses  the  F_Floating  format.   On
  OpenVMS  Alpha  systems,  REAL  can  take  one  of  two formats:
  F_Floating and IEEE S_Floating.  To specify a format, use either
  the FLOAT attribute or the /FLOAT command line qualifier.

  The default format on all OpenVMS systems is F_Floating.

2 - SINGLE

  The SINGLE  type  denotes  single-precision  real  values.   The
  SINGLE type is synonymous with the REAL type.

3 - F_FLOAT

  The F_FLOAT type  denotes  a  F_Floating  single-precision  real
  value regardless of the setting of the FLOAT attribute or /FLOAT
  command line qualifier.

4 - S_FLOAT

  The S_FLOAT type denotes a IEEE S_Floating single-precision real
  value regardless of the setting of the FLOAT attribute or /FLOAT
  command line qualifier.

  S_FLOAT is supported on OpenVMS Alpha systems only.

5 - DOUBLE

  The  DOUBLE  type  denotes  double-precision  real  values.   To
  indicate a double-precision real number, you must include a real
  number or an integer, the  letter  D  (or  d),  and  an  integer
  exponent with its minus sign or optional plus sign.  The largest
  DOUBLE value is denoted by MAXDOUBLE.  The smallest DOUBLE value
  is  denoted  by  MINDOUBLE.   EPSDOUBLE  denotes  the  result of
  subtracting 1.0d0 from the smallest DOUBLE value that is greater
  than 1.0d0.

  Example:  0D0
            4.371528665D-3

  On  OpenVMS  VAX  systems,  DOUBLE  exists   in   two   formats:
  D_Floating  and  G_Floating.   On  OpenVMS Alpha systems, DOUBLE
  exists in  three  formats:   D_Floating,  G_Floating,  and  IEEE
  T_Floating.

  To specify a format, you can use either the FLOAT  attribute  or
  the  /FLOAT command line qualifier.  On OpenVMS VAX systems, the
  default format is D_Floating.  On  OpenVMS  Alpha  systems,  the
  default format is G_Floating.

6 - D_FLOAT

  The D_FLOAT type  denotes  a  D_Floating  double-precision  real
  value regardless of the setting of the FLOAT attribute or /FLOAT
  command line qualifier.

7 - G_FLOAT

  The G_FLOAT type  denotes  a  G_Floating  double-precision  real
  value regardless of the setting of the FLOAT attribute or /FLOAT
  command line qualifier.

8 - T_FLOAT

  The T_FLOAT type denotes  an  IEEE  T_Floating  double-precision
  real  value  regardless of the setting of the FLOAT attribute or
  /FLOAT command line qualifier.

  T_FLOAT is supported only on OpenVMS Alpha Systems.

9 - QUADRUPLE

  The QUADRUPLE type denotes quadruple-precision real values.   To
  indicate  a  quadruple-precision real number, you must include a
  real number or an integer, the letter Q (or q), and  an  integer
  exponent with its minus sign or optional plus sign.  The largest
  QUADRUPLE  value  is  denoted  by  MAXQUADRUPLE.   The  smallest
  QUADRUPLE   value  is  denoted  by  MINQUADRUPLE.   EPSQUADRUPLE
  denotes the  result  of  subtracting  1.0q0  from  the  smallest
  QUADRUPLE value that is greater than 1.0q0.

  Example:  0.11435Q3
            3362Q2
            0.11825q-4

  On OpenVMS VAX systems, QUADRUPLE uses  the  H_Floating  format.
  On OpenVMS Alpha systems, QUADRUPLE uses the X_Floating format.

10 - H_FLOAT

  The H_FLOAT type denotes quadruple-precision real  values.   The
  H_FLOAT  type  is  synonymous with the QUADRUPLE type on OpenVMS
  VAX systems.

  H_FLOAT is supported only on OpenVMS VAX Systems.

11 - X_FLOAT

  The X_FLOAT type denotes quadruple-precision real  values.   The
  X_FLOAT  type  is  synonymous with the QUADRUPLE type on OpenVMS
  Alpha systems.

  X_FLOAT is supported only on OpenVMS Alpha Systems.