Communication software is used to provide remote access to systems and exchange files and messages in text, audio and/or video formats between different computers or users.
E-mail was introduced in the early 1960's as a way for multiple users of a time-sharing mainframe computer to communicate.
In the 1980s, a terminal emulator was a piece of software necessary to log into mainframes and thus access e-mail.
Prior to the rise of the Internet, computer files were exchanged over dialup lines, requiring ways to send binary files over communication systems that were primarily intended for plain text; programs implementing special transfer modes were implemented using various de facto standards, most notably Kermit.
Instant messaging featuring a buddy list and the notion of online presence was introduced by ICQ in 1996.