User interface

For the boundary between computer systems, see Interface (computing).

"Man–machine interface" redirects here. For other uses, see UI (disambiguation). For the communications protocol, see GSM Man-Machine Interface.

The Xfce desktop environment offers a graphical user interface following the desktop metaphor.

In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, while the machine simultaneously feeds back information that aids the operators' decision-making process. 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.

Generally, the goal of user interface design is to produce a user interface that makes it easy, efficient, and enjoyable (user-friendly) to operate a machine in the way which produces the desired result (i.e. maximum usability). This generally means that the operator needs to provide minimal input to achieve the desired output, and also that the machine minimizes undesired outputs to the user.

User interfaces are composed of one or more layers, including a human–machine interface (HMI) that typically interfaces machines with physical input hardware (such as keyboards, mice, or game pads) and output hardware (such as computer monitors, speakers, and printers). A device that implements an HMI is called a human interface device (HID). User interfaces that dispense with the physical movement of body parts as an intermediary step between the brain and the machine use no input or output devices except electrodes alone; they are called brain–computer interfaces (BCIs) or brain–machine interfaces (BMIs).

Other terms for human–machine interfaces are man–machine interface (MMI) and, when the machine in question is a computer, human–computer interface. Additional UI layers may interact with one or more human senses, including: tactile UI (touch), visual UI (sight), auditory UI (sound), olfactory UI (smell), equilibria UI (balance), and gustatory UI (taste).

Composite user interfaces (CUIs) are UIs that interact with two or more senses. The most common CUI is a graphical user interface (GUI), which is composed of a tactile UI and a visual UI capable of displaying graphics. When sound is added to a GUI, it becomes a multimedia user interface (MUI). There are three broad categories of CUI: standard, virtual and augmented. Standard CUI use standard human interface devices like keyboards, mice, and computer monitors. When the CUI blocks out the real world to create a virtual reality, the CUI is virtual and uses a virtual reality interface. When the CUI does not block out the real world and creates augmented reality, the CUI is augmented and uses an augmented reality interface. When a UI interacts with all human senses, it is called a qualia interface, named after the theory of qualia. CUI may also be classified by how many senses they interact with as either an X-sense virtual reality interface or X-sense augmented reality interface, where X is the number of senses interfaced with. For example, a Smell-O-Vision is a 3-sense (3S) Standard CUI with visual display, sound and smells; when virtual reality interfaces interface with smells and touch it is said to be a 4-sense (4S) virtual reality interface; and when augmented reality interfaces interface with smells and touch it is said to be a 4-sense (4S) augmented reality interface.

Overview

The Reactable musical instrument, an example of a tangible user interface

The user interface or human–machine interface is the part of the machine that handles the human–machine interaction. Membrane switches, rubber keypads and touchscreens are examples of the physical part of the Human Machine Interface which we can see and touch.

In complex systems, the human–machine interface is typically computerized. The term human–computer interface refers to this kind of system. In the context of computing, the term typically extends as well to the software dedicated to control the physical elements used for human–computer interaction.

The engineering of human–machine interfaces is enhanced by considering ergonomics (human factors). The corresponding disciplines are human factors engineering (HFE) and usability engineering (UE) which is part of systems engineering.

Tools used for incorporating human factors in the interface design are developed based on knowledge of computer science, such as computer graphics, operating systems, programming languages. Nowadays, we use the expression graphical user interface for human–machine interface on computers, as nearly all of them are now using graphics.

Multimodal interfaces allow users to interact using more than one modality of user input.

Terminology

A human–machine interface usually involves peripheral hardware for the INPUT and for the OUTPUT. Often, there is an additional component implemented in software, like e.g. a graphical user interface.

There is a difference between a user interface and an operator interface or a human–machine interface (HMI).

• The term "user interface" is often used in the context of (personal) computer systems and electronic devices.
  • Where a network of equipment or computers are interlinked through an MES (Manufacturing Execution System)-or Host to display information.
  • A human–machine interface (HMI) is typically local to one machine or piece of equipment, and is the interface method between the human and the equipment/machine. An operator interface, on the other hand, is the interface method by which multiple pieces of equipment, linked by a host control system, are accessed or controlled.
  • The system may expose several user interfaces to serve different kinds of users. For example, a computerized library database might provide two user interfaces, one for library patrons (limited set of functions, optimized for ease of use) and the other for library personnel (wide set of functions, optimized for efficiency).
• The user interface of a mechanical system, a vehicle or an industrial installation is sometimes referred to as the human–machine interface (HMI). HMI is a modification of the original term MMI (man–machine interface). In practice, the abbreviation MMI is still frequently used although some may claim that MMI stands for something different now. Another abbreviation is HCI, but is more commonly used for human–computer interaction. Other terms used are operator interface console (OIC) and operator interface terminal (OIT). However it is abbreviated, the terms refer to the 'layer' that separates a human that is operating a machine from the machine itself. Without a clean and usable interface, humans would not be able to interact with information systems.

In science fiction, HMI is sometimes used to refer to what is better described as a direct neural interface. However, this latter usage is seeing increasing application in the real-life use of (medical) prostheses—the artificial extension that replaces a missing body part (e.g., cochlear implants).

In some circumstances, computers might observe the user and react according to their actions without specific commands. A means of tracking parts of the body is required, and sensors noting the position of the head, direction of gaze and so on have been used experimentally. This is particularly relevant to