Each terminal in a full-duplex communication system comprises a computer-controlled display screen such as a CRT, at least one input device such as a keyboard, a mouse or a light pen and bidirectional communication system through which the terminals are interconnected. Each communication comprises a receiver for receiving display information received at the terminal from the remote terminal(s) and a transmitter for transmitting information to the remote terminal(s) where it is displayed. The invention enables multiple terminal users to simultaneously generate or modify a single common document in such a way that any changes to the document made by one user are instantaneously reflected at the terminals of all other users. To implement the present invention, each terminal comprises control processor which periodically reads its input means and communications system and uses the information contained therein to control the content of a local copy of the common document stored in its memory. Further, the control processor at each terminal also provides to its transmitter instructions which are transmitted to the remote terminals to change the copy of the common document at the remote terminal so that all the terminals maintain the same version of the common document. As a result of this arrangement, changes to a document that are made at the same time by the user at the local terminal and by the user at the remote terminal are entered into the local copies of the document at both terminals at substantially the same time so far as is discernable by the users. As a result, not only can each user interact with a single common document but it is also possible for each user to interact with the other users through the document without having to wait for one user to complete his entry of information. As a result, truly interactive communication is possible through the terminals.