Networks allow for several user and application communication functions. They enable a user to:
One of the most popular applications for computer networks is e-mail which allows a user to send a message to another user. The two users may be on the same system (in which case a communications network is not needed), different systems in different buildings, or even in different countries.
Through a communications network, one computer can mimic another and access information as if it were a different type of computer or terminal. Remote login capabilities allow users to log in to a remote system and access the same programs and files as if they were using the machine locally.
Networks also allow for the transfer of data from one system to another. Files, directories, and entire file systems can be migrated from one machine to another across a network, enabling remote backup of data, as well as assuring redundancy in case of machine failure.
Several different protocols have been devised to allow users and applications on one system to invoke procedures and applications on other systems, which is useful when distributing the burden for computer-intensive routines.