A user is an Intelligent agent|agent, either a human agent (end-user) or software agent, who uses a computer or Computer network|network Service (systems architecture)|service. A user often has a user account and is identified by a username (also user name). Other terms for username include login name, screen name (also screenname), Nickname#Computing|nickname (also nick), or handle, which is derived from the identical Citizen's Band radio term.Users are also widely characterized as the class of people that use a system without complete technical expertise required to understand the system fully. In Hacker (programmer subculture)|hacker-related contexts, such users are also divided into lusers and power users.
In projects in which the Actor (UML)|actor of the system is another system or a software agent, it is quite possible that there is no end-user for the system. In this case, the end-users for the system would be indirect end-users.