The classic historic early chatbots are ELIZA (1966) and PARRY (1972). More recent notable programs include A.L.I.C.E., Jabberwacky and D.U.D.E (Agence Nationale de la Recherche and CNRS 2006). While ELIZA and PARRY were used exclusively to simulate typed conversation, many chatbots now include functional features such as games and web searching abilities. In 1984, a book called The Policeman's Beard is Half Constructed was published, allegedly written by the chatbot Racter (though the program as released would not have been capable of doing so).
Dan uses an example of a text to speech bot that a user might operate within a car to turn windscreen wipers on and off, and lights on and off. The users’ natural language query is processed by the conversation service to work out the intent and the entity, and then using the context, replies through the dialog in a way that the user can understand.