@@commands = {
        :showhelp => :show_help,
        :help => :help,
        :shuffle => :shuffle,
        :new => :new_cmd,
        :quit => :quit,
        :unknown => :unknown
    }

    def execute (cmd)

        #save last entered command
        @last_command = cmd

        # check in the dictionary
        cmd = cmd.to_sym
        opcode = ( @@commands.has_key?(cmd) ? @@commands[cmd] : :unknown )
        puts opcode.inspect

        # call method
        self.send(opcode)

    end