All these things are examples of asynchronous, or non-interactive communication. In non-interactive communication, you are sending and receiving whole units of communication, the equivalent of files or messages, which is analogous to regular surface mail. For many years, the standard for interactive communication was to use either telnet or ftp. Both telnet and ftp are computer programs, and there are various versions of these programs. With telnet , you are permitted to log on to a file server from a remote location.
Some file servers require user ids and others permit guest logins.
In either case, however, the significance of telnet is that it permits you to do at a distance with a file server what you might otherwise have only local access to. The ftp program provides a set of commands which allows users to get files from a remote file server and put files on a remote file server. The program allows users to transfer both text files and binary files. Learning to use ftp presents one of the greatest challenges to educators, but holds out a high promise for opening up one path to the whole Internet world for the mining of free classroom resources. There are many so-called anonymous ftp sites that allow users to download free software and other valuable information.