The tutorial consists of three executables that together make up a primitive 
chatbox:
* Chatter: Use this executable to send chat messages to the chatbox.
* MessageBoard: Use this executable to view all available chatmessages.
* UserLoad: Use this executable to keep track of when users join and leave 
  the chatbox.

Some executables support optional command-line parameters. When these 
parameters are not specified, default values are used instead. The 
optional parameters and their meaning are specified below:

Chatter [userid] [username]
  userid:   an integer number that uniquely identifies the sender of a message.
            (Transmit a message with userid = -1 to terminate the MessageBoard.)
  username: the user-name other chatters will see when they receive one of your
            chat messages.
            
MessageBoard [userid]
  userid:   block messages from a user identified by this id. You can use this
            to prevent seeing your own messages appear on your own 
            MessageBoard.
