1. An application executing terminal comprising: a start request means for accepting a selection of an application to be started to make a start request for start of said application; an application executing means for executing an application for which a start request has been made by said start request means; a button assignment request means for making a request for assignment of an operation button to an application currently being executed by said application executing means; a button assignment control means for carrying out a process of assigning an operation button to an application for which a request for assignment of the operation button has been made by said button assignment request means, and for managing an assignment relation between the operation button and the application; an operation information receiving means for receiving operation information indicating an operation button operated by a user; and an event notification means for inquiring of said button assignment control means about an application corresponding to the operation button indicated by the operation information received by said operation information receiving means to notify a predetermined event associated with said application to said application executing means.