四捨五入是---round off , e.g. If 25.587 is rounded off to

                      the second decimal place, it becomes 25.59.

無條件進位是------round up , e.g. If one point five is rounded up

                     to the nearest whole digit , it becomes two .

無條件捨去是------round down , e.g. If one point four is rounded

                     down to the nearest whole digit, it becomes one .