An electronic device comprising: a main body ; a cover part (270; 266a) normally coupled to the main body and configured to be attached to and detached from the main body ; and a controller configured to: output a first signal for determining a coupling state of the cover part (270; 266a) with respect to the electronic device ; receive a second signal being distorted relative to the first signal; determine the coupling state of the cover part (270; 266a) with respect to the electronic device based on distortion of the second signal relative to the first signal; and output a notification message related to coupling of the cover part (270; 266a), CHARACTERISED IN THAT the controller is further configured to: determine whether an incompletely coupled portion exists between the cover part (270; 266a) and the electronic device based on the distortion of the second signal relative to the first signal, wherein at least part of the first signal is transmitted through the incompletely covered portion between the cover part and the main body, when the cover part is incompletely coupled to the main body; determine a location of the incompletely covered portion, and output the notification message related to the location of the incompletely covered portion. a main body ; a cover part (270; 266a) normally coupled to the main body and configured to be attached to and detached from the main body ; and a controller configured to: output a first signal for determining a coupling state of the cover part (270; 266a) with respect to the electronic device ; receive a second signal being distorted relative to the first signal; determine the coupling state of the cover part (270; 266a) with respect to the electronic device based on distortion of the second signal relative to the first signal; and output a notification message related to coupling of the cover part (270; 266a), output a first signal for determining a coupling state of the cover part (270; 266a) with respect to the electronic device ; receive a second signal being distorted relative to the first signal; determine the coupling state of the cover part (270; 266a) with respect to the electronic device based on distortion of the second signal relative to the first signal; and output a notification message related to coupling of the cover part (270; 266a), CHARACTERISED IN THAT the controller is further configured to: determine whether an incompletely coupled portion exists between the cover part (270; 266a) and the electronic device based on the distortion of the second signal relative to the first signal, wherein at least part of the first signal is transmitted through the incompletely covered portion between the cover part and the main body, when the cover part is incompletely coupled to the main body; determine a location of the incompletely covered portion, and output the notification message related to the location of the incompletely covered portion. determine whether an incompletely coupled portion exists between the cover part (270; 266a) and the electronic device based on the distortion of the second signal relative to the first signal, wherein at least part of the first signal is transmitted through the incompletely covered portion between the cover part and the main body, when the cover part is incompletely coupled to the main body; determine a location of the incompletely covered portion, and output the notification message related to the location of the incompletely covered portion. <EOS>