Interactive terminal is a terminal for exchanging information between man and machine. Its working mode is simple, and it only has the function of inputting and outputting information. It can't complete any information processing actions by itself, nor can it correct, explain or change data information from all aspects. Receiving letters or sending letters can only be started by pressing buttons or messages sent by the central host. It works slowly and usually consists of an teletypewriter or keyboard display device plus a modem.