PURPOSE: To minimize the amount of communication between a terminal and a host computer regardless of the size of a source text to be processed by retrieving only the source text existing in the terminal and retrieving following texts in the host computer side when the source text can not be discovered.

CONSTITUTION: When a terminal character string retrieving means 1 requests the source text, a terminal text referring means 2 judges whether the requested source text exists in a terminal text storing area 4 or not. When the source text exists, the source text is returned and when the source text does not exist, a retrieval requesting means 5 requests the retrieval to a host computer 100 side. Then, a host character string retrieving means 8 retrieves a row including a requested character string out of a host text storing area 10 and displays the row in the terminal. Thus, the amount of the communication between the terminal and hot computer can be made minimum regardless of the size of the source text to be processed.