Abstract: A power management method for a PDA (personal digital assistant) which can be connected with an external communication terminal is described. Upon detecting power-on of the external communication terminal, the PDA detects a battery voltage of the PDA and compares the battery voltage with a reference voltage which is slightly higher than an inoperable voltage of the PDA. If the battery voltage is lower than the reference voltage, the PDA generates a low-voltage alarm message. Otherwise, if the battery voltage is higher than the reference voltage, the PDA supplies electric power to the external communication terminal.

Abstract: A map data base management system comprises a map data base storage unit for storing a map index file so that with respect to regions partitioning each of maps drawn on a plurality of scales involved with the same geographical area, an individual region index is designated to a region, in the manner that a region index for designating each region constituting a relatively large-scale map determines region indices for designating a plurality of regions constituting a map of a scale just below the relatively large-scale; and a map data file so that among regions designated by region indices, individual map data is designated by a scale and a region index, in the manner that each region having land in a corresponding scale map has corresponding map data and each region having no land in a corresponding scale map has no map data.

Abstract: A method for processing a name when converting a numerical map of a low level into a numerical map of a high level in a geographic information system includes the steps of: sequentially determining a main name which is a criterion of comparison and a sub name which is an object of comparison according to priority with respect to names contained in the numerical map of the low level, and generating a main name box and a sub name box according to a position and an area in which the main name and the sub name are displayed on the numerical map of the high level; and checking whether a part or all parts of the sub name box is overlapped with the main name box, and erasing a corresponding name and a name designating coordinate point when there is an overlapped part.