An electronic device comprising: a storage configured to store a shared file shared between a plurality of virtual devices; and a controller configured to: create an alternative file by copying the shared file when a first virtual device of the plurality of virtual devices makes a request for modifying the shared file, modify the shared file based on the modification request of the first virtual device; wherein the controller is further configured to: notify a second virtual device of the modification of the shared file and the creation of the alternative file, including transmitting information about the first virtual device which makes the request for modifying the shared file, the shared file subjected to the modification request, the alternative file, and address information for referring to the modified shared file and the alternative file, to the second virtual device; receive a selection from the second virtual device for selectively referring to the created alternative file or the modified shared file, wherein the second virtual device is configured to determine whether the shared file is modified by the first virtual device having modification authority on the basis of the information received from the controller, and to selectively refer to the modified shared file or the alternative file on the basis of the determination. a storage configured to store a shared file shared between a plurality of virtual devices; and a controller configured to: create an alternative file by copying the shared file when a first virtual device of the plurality of virtual devices makes a request for modifying the shared file, modify the shared file based on the modification request of the first virtual device; wherein the controller is further configured to: notify a second virtual device of the modification of the shared file and the creation of the alternative file, including transmitting information about the first virtual device which makes the request for modifying the shared file, the shared file subjected to the modification request, the alternative file, and address information for referring to the modified shared file and the alternative file, to the second virtual device; receive a selection from the second virtual device for selectively referring to the created alternative file or the modified shared file, wherein the second virtual device is configured to determine whether the shared file is modified by the first virtual device having modification authority on the basis of the information received from the controller, and to selectively refer to the modified shared file or the alternative file on the basis of the determination. create an alternative file by copying the shared file when a first virtual device of the plurality of virtual devices makes a request for modifying the shared file, modify the shared file based on the modification request of the first virtual device; wherein the controller is further configured to: notify a second virtual device of the modification of the shared file and the creation of the alternative file, including transmitting information about the first virtual device which makes the request for modifying the shared file, the shared file subjected to the modification request, the alternative file, and address information for referring to the modified shared file and the alternative file, to the second virtual device; receive a selection from the second virtual device for selectively referring to the created alternative file or the modified shared file, wherein the second virtual device is configured to determine whether the shared file is modified by the first virtual device having modification authority on the basis of the information received from the controller, and to selectively refer to the modified shared file or the alternative file on the basis of the determination. notify a second virtual device of the modification of the shared file and the creation of the alternative file, including transmitting information about the first virtual device which makes the request for modifying the shared file, the shared file subjected to the modification request, the alternative file, and address information for referring to the modified shared file and the alternative file, to the second virtual device; receive a selection from the second virtual device for selectively referring to the created alternative file or the modified shared file, wherein the second virtual device is configured to determine whether the shared file is modified by the first virtual device having modification authority on the basis of the information received from the controller, and to selectively refer to the modified shared file or the alternative file on the basis of the determination.