Battery information is transmitted from a recording and playback apparatus to a host computer. In the host computer, based on the time for which the operation can be continued, corresponding to the current operating status and the remaining battery level, stored in the battery information, a warning is output, the data of a cache memory is written, data writing prohibition is set, and a forced closing process is performed. With this construction, in a system formed of a recording and playback apparatus, such as a CD-R/RW drive unit, and a personal computer, a proper system operation corresponding to the remaining battery level of the recording and playback apparatus is obtained, and the data recorded on the recording medium is prevented from being destroyed as a result of operation stopping due to, for example, the remaining battery level becoming zero.