Round up/down????

Round up即是:
例：把123456取近似值至千位
　　=124000
所以只需要把要求的位置+1而後面的數全部變0
Round down即是:
例：把123456取近似值至千位
　　＝123000
所以只要把需要的位置後面的所有數全部變０

Round up is rounding to the nearest integer bigger than it..
E.g. 4.3456 round up to 5.

Round down is rounding to the nearest integer smaller than it
E.g 4.3456 round down to 4