Abs function 

  DECLARATION:  Abs(X)

      PURPOSE:  Returns the absolute value of the argument.

         UNIT:  System

  RESULT TYPE:  Same as argument.

      REMARKS:  X must be an integer- or real-type expression.  The result
                will be of the same type as X.

      EXAMPLE:  Var
                   x : Real;
                   i : Integer;

                Begin
                   x := -2.69;
                   i := -156;
                   WriteLn('x = ',Abs(x));   { displays ABS value }
                   i := Abs(i);              { converts to ABS value }
                   WriteLn('i = ',i);
                End.