A navigation system and a computer program are capable of changing the role of an apparatus that implements navigation in accordance with its performance and circumstances, and achieving single navigation, in a coordinated fashion, with multiple apparatuses to which their roles are appropriately distributed. At least one apparatus is provided with: a plurality of function executing units that independently have different functions for navigation, each of the function executing units performing processing associated with the function in response to a given instruction and returning a result of the processing; and an instruction unit that provides an instruction to each of the plurality of function executing units, and receives a result of the processing returned in response to the instruction; the instruction unit of the apparatus provides an instruction to one or more of the plurality of function executing units according to a procedure suitable for a purpose to be accomplished as to navigation, and outputs navigation data based on a result of processing returned in response to the instruction.