VMS Help PASCAL, Expressions, Operators, Type Cast Operator  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The type cast operator changes the context in which  a  variable
  or an expression of a certain data type can be used.  The actual
  representation of the object being cast is not  altered  by  the
  type  cast  operator.  Compaq Pascal overrides the type only for
  the duration of one operation.  It  has  one  of  the  following
  forms:

     variable-identifier :: type-identifier

     (expression) :: type-identifier

  The type cast operator (::) separates the name of  the  variable
  or  an  expression in parentheses from its target type, the type
  to which it is being cast.

  Example:
     TYPE
        F_Float = PACKED RECORD
                  Frac1 : 0..127;
                  Expo  : 0..255;
                  Sign  : Boolean;
                  Frac2 : 0..65535;
                  END;

     VAR
        A : REAL;

     {In the executable section:}
     A :: F_Float.Expo := A :: F_Float.Expo + 1;

  The  record  type  'F_Float'  illustrates  the  layout   of   an
  F_floating  real  number.   The  real  variable 'A' is cast as a
  record of this type, allowing access to  the  fields  containing
  the  mantissa, exponent, sign, and fraction of 'A'.  Adding 1 to
  the field containing the exponent would give the same result  as
  multiplying 'A' by 2.0.