Why are IP address classified into classes?

For classful addressing, the first octet identifies the class to which it belongs. There is also a way of looking at the first few bits of the first octet, but that makes it more difficult.

For an IpV4 address, you have 4 octets for the IP address. Looking at the first octet, to determine the range, use the following:

1 - 126 class A

127 local loopback address

128 - 191 class B

192 - 223 class C

224 - 239 class D

240 - 254 class E