A user information registration program stored in a first memory of a terminal unit, transferred to a host device to which the terminal unit is connected, and executed on the host device, wherein the terminal unit inputs information and the first memory stores the input information, the program comprising first and second programs (302, 304), wherein: the first program is an automatic execution program that is loaded and automatically activated on the host device when the terminal unit is connected to the host device, and the second program is an application program attached to the terminal unit; the first program causes the host device to execute a step of determining whether the second program is already installed on the host device; (a) if it is determined in the step of determining that the second program is not installed on the host device, the first program causes the host device to execute: (a-1) a step of retrieving, from the terminal unit, device identification information that identifies the terminal unit, (a-2) a step of obtaining (S1000, S704, S1002) user information by searching for user information through the host device if the processing unit of the host device determines that user information is retrievable from the host device, or by displaying, on a display unit of the host device, an input screen that promotes input of the user information and accepting, through an input device of the host device, the input operation of said user information by the user if the processing unit of the host device determines that user information is not retrievable from the host device, (a-3) a step of storing (S710, S712), in a second memory of the host device, the device identification information and the user information obtained by the step of obtaining user information, associating the device identification information and the user information to each other, (a-4) a step of transferring, to a server via a network, the device identification information and the user information obtained by the step of obtaining user information, and (a-5) a step of installing the second program on the host device. (a) if it is determined in the step of determining that the second program is not installed on the host device, the first program causes the host device to execute: (a-1) a step of retrieving, from the terminal unit, device identification information that identifies the terminal unit, (a-2) a step of obtaining (S1000, S704, S1002) user information by searching for user information through the host device if the processing unit of the host device determines that user information is retrievable from the host device, or by displaying, on a display unit of the host device, an input screen that promotes input of the user information and accepting, through an input device of the host device, the input operation of said user information by the user if the processing unit of the host device determines that user information is not retrievable from the host device, (a-3) a step of storing (S710, S712), in a second memory of the host device, the device identification information and the user information obtained by the step of obtaining user information, associating the device identification information and the user information to each other, (a-4) a step of transferring, to a server via a network, the device identification information and the user information obtained by the step of obtaining user information, and (a-5) a step of installing the second program on the host device. (a-1) a step of retrieving, from the terminal unit, device identification information that identifies the terminal unit, (a-2) a step of obtaining (S1000, S704, S1002) user information by searching for user information through the host device if the processing unit of the host device determines that user information is retrievable from the host device, or by displaying, on a display unit of the host device, an input screen that promotes input of the user information and accepting, through an input device of the host device, the input operation of said user information by the user if the processing unit of the host device determines that user information is not retrievable from the host device, (a-3) a step of storing (S710, S712), in a second memory of the host device, the device identification information and the user information obtained by the step of obtaining user information, associating the device identification information and the user information to each other, (a-4) a step of transferring, to a server via a network, the device identification information and the user information obtained by the step of obtaining user information, and (a-5) a step of installing the second program on the host device.