As the Internet started, the original Classful addressing procedure became a limitation. The IP address space was being terminated because all networks had to select one of three possible sizes. Many addresses were not used.
Two new methods were invented to overcome the limitations, which are as given:
Instead of having three different address classes, allow the division between suffix and prefix to occur on an arbitrary boundary. The classless addressing scheme answers the problem by allowing an ISP to give a prefix. Prefix is 28 bits long.