The term ‘IP or Internet Protocol’ refers to the Internet layer of the Internet Protocol Suite which performs the task of exchanging information between host and destination addresses. The fourth version of Internet Protocol, or IPv4, is the fourth version of IP creation. It is also the first edition of the protocol to ever be deployed extensively. look at this site
In IPv4 address groups is usually split into two sections at the beginning: the network identifier and the host identifier. When this was not found compatible, another address was redefined in such a way that the anomalies of the first method might be exceeded. Thus fell into being the technique of building a collection of networks, widely recognized as elegant networking. This method divides the address space for version 4 of Internet Protocol into five different classes of addresses, class A, B , C , D and E. Every class determines either network capacity, or network multicast. Class A, B , and C also have separate bit lengths to define a specific network, Class D is used for multicast addressing and Class E is reserved for potential purposes.
The first class selected in the IPv4 address group, which is Class A, contains all the addresses in which the most important bit is 0. For this, the nest seven bits give the network number accommodating a total of 128 networks including the zero network and the current IP network already assigned. The two most important bits 0 and 1. were addresses in the Class B network The next 14 bits of address is given the network address for this network thereby leaving 16 bits for numbering host on the network for a total of 65536 addresses per network. The third class in the IPv4 address range, i.e. Class C was listed with 3 bits, 1, 1, and 0, leaving the next 21 bits per network to networks with 256 local addresses. The fourth division came in with the leading bit chain, 111 and was left to tackle multicast. The 1111 unit, or Class E, was eventually left for future experiments.
Although IPv4 network classes, the first architecture system expanded the Internet’s addressing capability, the IP address shortage was not preventable. The issue was that many places wanted bigger address blocks than the one given by a Class C network. They got Class B block as a result but that was far more than expected again. The unassigned portion of the Class B network was thus going in vain.
Later this IPv4 class system was replaced officially with Classless Inter-Domain Routing (CIDR). This system allowed the repartitioning of any address space so that the users could easily be assigned smaller as well as larger blocks of addresses.