A device status monitoring system and method for a POS (point of sale) terminal system, in which an OPOS (OLE for Retail POS) object continuously records changes in device status to a file. A control system (OPOS object) includes a first object (control object) providing an interface for a device class to an application program, and a second object (service object) providing an interface for a specific device to the first object. The second object has commands for executing a process for: receiving status data indicating a device status from the specific device; detecting, as status change data, status data that changed by comparing the received status data with previously received status data; determining, based on predefined recording conditions, whether the status change data is data to be recorded in a log file; generating log data for recording the status change by converting the status change data to a text message and adding time information to the text message; and storing the log data to a log file specified by the recording conditions.