PURPOSE: To retrieve the alias of a file at a high speed by setting the alias at a file control part of the file.

CONSTITUTION: The alias of a file 11 is stored in a file control part 13 of the file 11. If the file designated by the name designated by a user is identical with the file 11, the alias of the file is stored in the part 13 of the file 11. Therefore the alias of the file 11 controlled at the part 13 can be immediately obtained when the contents of the part 13 are read. Thus no problem occurs at all even if no file having an alias exists in a data area. As a result, the alias of a file is retrieved at a high speed and the data area can be effectively used.