Distinguish the between intranet and official IP addresses

Question

How can I find out whether a given IP address is an official internet address or an internal intranet IP address?

Answer 1

10.0.0.0 - 10.255.255.255` (10.0.0.0/8, former Class A)

172.16.0.0 - 172.31.255.255` (172.16.0.0/12, former Class B)

192.168.0.0 - 192.168.255.255` (192.168.0.0/24, former Class C)

Founding out that given IP belongs to that, depends in what form do you have given IP. The best way to use bytes.