0 a device or program that stops people from seeing or using information on a computer without permission while it is connected to the internet -- (计算机的)防火墙
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路,一步步也能走完,再短的路,不迈开双脚也无法到达。