File sharing is the public or private sharing of computer data or space in a network with various levels of access privilege. While files can easily be shared outside a network (for example, simply by handing or mailing someone your file on a diskette), the term file sharing almost always means sharing files in a network, even if in a small local area network. File sharing allows a number of people to use the same file or file by some combination of being able to read or view it, write to or modify it, copy it, or print it. Typically, a file sharing system has one or more administrators. Users may all have the same or may have different levels of access privilege. File sharing can also mean having an allocated amount of personal file storage in a common file system.
File sharing has been a feature of mainframe and multi-user computer systems for many years. With the advent of the Internet, a file transfer system called the File Transfer Protocol (FTP) has become widely-used. FTP can be used to access (read and possibly write to) files shared among a particular set of users with a password to gain access to files shared from an FTP server site. Many FTP sites offer public file sharing or at least the ability to view or copy files by downloading them, using a public password (which happens to be "anonymous"). Most Web site developers use FTP to upload new or revised Web files to a Web server, and indeed the World Wide Web itself can be thought of as large-scale file sharing in which requested pages or files are constantly being downloaded or copied down to the Web user.
More usually, however, file sharing implies a system in which users write to as well as read files or in which users are allotted some amount of space for personal files on a common server, giving access to other users as they see fit. The latter kind of file sharing is common in schools and universities. File sharing can be viewed as part of file systems and their management.
Any multi-user operating system will provide some form of file sharing. Among the best known network file systems is (not surprisingly) the Network File System (NFS). Originally developed by Sun Microsystems for its UNIX-based systems, it lets you read and, assuming you have permission, write to sharable files as though they were on your own personal computer. Files can also be shared in file systems distributed over different points in a network. File sharing is involved in groupware and a number of other types of applications.
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