Abstract: In a digital map display zooming method for enlarging and reducing a displayed portion of a digital map as map information in digital form within a display screen, continuous enlarging operation and continuous reducing operation of the displayed portion of the digital map within the display screen are designated by operating the first designating part and the second designating part of a pointing device, respectively.

Abstract: In this invention, data track of a magneto-optical disc is divided into a volume management area and an extent area to record data of file into the extent area, and to record directory management information and file management information into the volume management area. The volume management area is caused to consist of 32 clusters. Data allocation unit of the volume management area is caused to be 2 k bytes and data allocation unit in the extent area is caused to be 8 k bytes. Relative recording location within the volume management area of sub directory is recorded, as directory information, into the volume management area. Thus, this invention can quickly carry out access.

Abstract: When information to be recorded is encrypted by using an encryption key, an encryption key based on inherent information inherent in a recording medium is generated. The information to be recorded on the recording medium is encrypted based on the encryption key. The inherent information inherent in the recording medium is a specific information on a disk. When an encrypted information recorded on a recording medium is decrypted, there are reproduced from a recording medium a first file storing information encrypted by using an encryption key generated based on a random data to be inserted into a predetermined portion of the encrypted information to be recorded on a recording medium and a second file storing data indicative of a predetermined portion of the random data to be inserted into a predetermined portion of the encrypted information.

Abstract: An anti-freezing device for use in water supply conduits, which includes a driving chamber for imparting a drive to a main valve which is moved by the volumetric expansion due to the freezing of water therein so that the main valve is separated from a valve seat thereby to discharge water in the conduit outside therethrough. The flowing movement of water in the conduit prevents it from freezing.