A user is a person who utilizes a computer or Computer network service. Users of computer systems and software products generally lack the technical expertise required to fully understand how they work.Jargon File entry for use advanced features of programs, though they are not necessarily capable of computer programming and system administration.
A user often has a user account and is identified to the system by a username (or user name). Other terms for username include login name, screenname (or screen name), account name, nickname (or nick) and handle, which is derived from the identical Citizen's Band radio term.
In user-centered design, personas are created to represent the types of users. It is sometimes specified for each persona which types of user interfaces it is comfortable with (due to previous experience or the interface's inherent simplicity), and what technical expertise and degree of knowledge it has in specific fields or . When few constraints are imposed on the end-user category, especially when designing programs for use by the general public, it is common practice to expect minimal technical expertise or previous training in end users.
The end-user development discipline blurs the typical distinction between users and developers. It designates activities or techniques in which people who are not professional developers create automated behavior and complex data objects without significant knowledge of a programming language.
Systems whose actor is another system or a software agent have no direct end users.
Once the user has logged on, the operating system will often use an identifier such as an integer to refer to them, rather than their username, through a process known as identity correlation. In Unix systems, the username is correlated with a user identifier or user id.
Computer systems operate in one of two types based on what kind of users they have:
Each user account on a multi-user system typically has a home directory, in which to store Computer file pertaining exclusively to that user's activities, which is protected from access by other users (though a system administrator may have access). User accounts often contain a public user profile, which contains basic information provided by the account's owner. The files stored in the home directory (and all other directories in the system) have file system permissions which are inspected by the operating system to determine which users are granted access to read or execute a file, or to store a new file in that directory.
While systems expect most user accounts to be used by only a single person, many systems have a special account intended to allow anyone to use the system, such as the username "anonymous" for anonymous FTP and the username "guest" for a guest account.