Abstract: The present invention provides a memory card (1) using a write-once memory IC (17), such as PROM. In this memory IC (17), an entity data recording area, where the entity data of a file is recorded, and a management data recording area, where management data for supervising the recorded files in accordance with a hierarchical directory structure is recorded, are formed at the outset. In the management data recording area, a file entry specifying the files recorded in the memory card (1), a root entry specifying the uppermost order directory in the hierarchical directory structure and a sub-entry specifying sub-directories in the hierarchical directory structure, are recorded as management data in association with the files, root directory and the sub-directories generated, respectively.

Abstract: An image rendering device holds a table which contains color and brightness values at positions specified by two-dimensional coordinates, where the color values are aligned so as to express a gradation of color tone along one coordinate axis of the two-dimensional coordinate, and the brightness values are aligned so as to express a gradation of brightness along the other coordinate axis. The image rendering device finds parameters corresponding to at least one of color and brightness of a polygon to be rendered, and generates an address for referencing a two-dimensional coordinate corresponding to each pixel composing the polygon based on the parameters. The image rendering device then acquires from the table color and/or brightness values corresponding to the address for referencing the two-dimensional coordinate. This successfully realizes natural expression by the image rendering device without preparing in advance a huge number of textures.

Abstract: An electronic device that includes: a peripheral circuit which is driven by a drive voltage, a battery which supplies the drive voltage, a memory which is driven by the battery, and a CPU operable to write data to the memory, read the data which has been written, compare the written data with the read data, and determine whether or not the drive voltage has dropped below a minimum operable voltage based on the comparison.