PURPOSE: To facilitate the operation to add and put in the new details to a reference table by retrieving forward and reversely the pointers showing the addresses corresponding each key word for a data buffer storing the key words.

CONSTITUTION: A keyword forward registration control part 10 and a keyword reverse registration control part 11 can retrieve forward and reversely the pointers showing the addresses corresponding to each key word of a data buffer 9 which stores the key words registered into a data table. Thus a key word like 'other' starts the part 11, and a normal key word starts the part 10. Thus the key words can be registered in the different orders. As a result, the operation is facilitated for addition and insertion of the new details to a reference table.