Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The user interface of an application software or operating system is sometimes described as redundant if the same task can be executed by several different methods. For example, a user is often able to open or save a project by navigating a menu with the mouse or keyboard, by clicking a single button with the mouse, or by entering a key stroke. In the industrial design field of human-machine interaction, the user interface is (a place) where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the machine which aids the operator in making operational decisions. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls. and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.