Class A
The InterNIC reserves Class A IP addresses for governments throughout the world.
Class A addresses, when written in binary format, will always begin with a zero.
You can tell what class an Internet address belongs to by looking at its first octet. Class A addresses in decimal notation will have a 1 to 126 as their first octet.
The first Class A address that can be assigned is 1.0.0.0 (decimal) or 00000001.00000000.00000000.00000000 (binary).
The last Class A address that can be assigned is 126.0.0.0 in decimal notation, which is 01111110.0000000.00000000.00000000 in binary format.