SizeOf function

  DECLARATION:  SizeOf(X);

      PURPOSE:  Returns the number of bytes occupied by the argument

         UNIT:  System

  RESULT TYPE:  Word

      REMARKS:  X may be either a variable reference or a type identifier.
                SizeOf should always be used when passing values to FillChar
                GetMem, Move etc.. (ie FillChar S, SizeOf(S), 0);)