A Unix program and protocol supporting conversation between two or more users who may be logged into the same computer or different computers on a network. Variants include ntalk, ytalk, and ports or emulators of these programs for other platforms.
Unix has the talk program and protocol and its variants xtalk and ytalk for the X Window System; VMS has phone; Windows for Workgroups has chat. ITS also has a talk system. These split the screen into separate areas for each user.
Users of such systems are said to be in talk mode which has many conventional abbreviations and idioms. Most of these survived into chat jargon, but many fell out of common use with the migration of user prattle from talk-like systems to chat systems in the early 1990s. These disused talk-specific forms include:
"JAM"/"MIN" - just a minute
"OO" - "over and out" - end of conversation.
"R U THERE?" - are you there?
"SEC" - wait a second.