Numbers are just great for computers but they are very taxing on humans' memories. People want to use alphabetic names both for people's usernames on computers, as well as for hosts and even networks. For example, the fictitious name

joe@gandalf.net17.att.com

has all the necessary components, only in an alphabetic format. Joe is the name of the user, the recipient of email or "talk." gandalf is the name of the computer on which Joe has an account. (Many computer geeks who run networks were J.R.R. Tolkien fans in the early 1970s so they often use characters from "The Lord of the Rings" and "The Hobbit." Gandalf was the chief wizard of this series of books.) Net17 is the name of the subnet while att.com is the name of the overall network.

Ironically, the numerical IP address begins with the network number, followed by subnet followed by host. Thus, it proceeds from the most general to the specific, whereas the alphabetic form of addresses usually go from the most specific to the most general in a backwards fashion.