An input/output device enables a system to adapt its operation to the user's learning the system without interfering with what the user has already learned about operating the system. In an input/output device enabling a system to adapt to how frequently the user uses particular functions, a storage unit 12 accumulates information about the operations the user performs, a user learning evaluation unit 13 determines if the user has learned each function based on the input operation history accumulated by the storage unit 12, and a menu display position adjustment unit 14 leaves the menu display position unchanged for any function the user learning evaluation unit 13 determines the user has learned, and rearranges the menu display positions of only those functions the user learning evaluation unit 13 determines the user has not learned in descending order of the frequency of execution based on the input operation history stored by the storage unit 12.