Talk is an effective poor man's tool to support the principle of ``being there''. MUD (Multiuser Dungeons)  shows how it is possible to provide more sophisticated support for this principle by creating a virtual environment that simulates a physical meeting environment. Unlike several other applications we shall see later, the original intention was not to support predefined teams and goals but instead to provide a meeting ground for users unaware of each other who could play games, socialise, or so do some actual work. MUD provides the abstraction of rooms and allows users to enter and leave them. It offers each user two basic commands, say and emote. To illustrate, let us take the example from : If user Munchkin, executes:
say Can anyone hear me?he sees the echo
You say, ``Can anyone hear me''while others in the room see:
Munchkin says, ``Can anyone hear me?''If Munchkin executes
emote smilesthen everyone else in the room sees
Munchkin smilesA variation of the say command, the whisper command, allows a user to direct a comment to a specific user. Thus, if Munchkin types,
whisper ``I wish he'd just go away ..'' to Frebblethen only Frebble sees the comment. Thus MUD is also example of a tool that integrates talk and mail, which we shall study in more depth later.
When a user enters or leaves a room or leaves/joins a conference, messages are printed on the screens of other users in the room. The name and gender used to identify users are those they explicitly told MUD about. Typically, users do not use their real name and sometimes not their real gender. A user also gives MUD a (typically fictitious) textual description, which others can examine by executing the look command. A special @who command tells a user the names, connect time, idle time, and location of the users connected to MUD.
MUDs have special users called ``wizards'' who correspond to superusers. An ordinary player can be transformed into a wizard by another wizard. Wizards can punish other users for socially unacceptable behavior. They can prevent users from connecting or executing certain commands, changing their names and descriptions to unpleasant ones, or ``humiliate'' them by moving them to a public place.
MUD is extensible and allows users to add their own objects to the database such as rooms, exits, and notes. Thus, the MUD idea also combines artifact-based collaboration with session-management.
Several variations and extensions of the MUD idea are currently being pursued .