POS terminal apparatus

A management method of a usage amount of an external device connected to a POS (point-of-sale) terminal apparatus, comprising:

• running an application in the POS terminal apparatus;
• determining whether the external device is capable of counting a first value indicating a usage amount of the external device;
• acquiring the first value from the external device in response to a first command from the application when it is determined that the external device is capable of counting the first value;
• retaining a second value indicating the usage amount of the external device;
• notifying the second value to the application in response to a second command from the application;
• counting the second value in accordance with a third command sent from the application to the external device when it is determined that the external device is not capable of counting the first value;
• and
• updating the second value with a third value which is obtained by a fourth command from the application with reference to the acquired first value,
• wherein the first value is retained when the second value is updated with the third value.

A POS (point-of-sale) terminal apparatus adapted to be connected to an external device, comprising:

• a general purpose computer including a processor and a memory, the general purpose computer running an application;
• a device manager capable of communicating with the external device, the device manager determining whether the external device is capable of counting a first value indicating a usage amount of the external device, and acquiring the first value from the external device in response to a first command from the application when it is determined that the external device is capable of counting the first value;
• a counter retaining a second value indicating the usage amount of the external device and notifying the second value to the application in response to a second command from the application, the counter virtually counting the second value in accordance with a third command sent from the application to the external device when it is determined that the external device is not capable of counting the first value;
• and
• an updater updating the second value with a third value which is obtained by a fourth command from the application with reference to the first value acquired by the device manager,
• wherein the first value is retained when the second value is updated with the third value.