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.
Generally, the goal of human-machine interaction engineering is to produce a user interface which makes it easy, efficient, enjoyable to operate a machine in the way which produces the desired result. 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 human.
Ever since the increased use of personal computers and the relative decline in societal awareness of heavy machinery, the term user interface has taken on overtones of the (graphical) user interface, while industrial control panel and machinery control design discussions more commonly refer to human-machine interfaces.
Other terms for user interface include human-computer interface (HCI) and man-machine interface (MMI).
To work with a system, users have to be able to control and assess the state of the system. For example, when driving an automobile, the driver uses the steering wheel to control the direction of the vehicle, and the accelerator pedal, brake pedal and gearstick to control the speed of the vehicle. The driver perceives the position of the vehicle by looking through the windshield and exact speed of the vehicle by reading the speedometer. The user interface of the automobile is on the whole composed of the instruments the driver can use to accomplish the tasks of driving and maintaining the automobile.
There is a distinct difference between User Interface versus Operator Interface or Human Machine Interface (HMI).
In science fiction, HMI is sometimes used to refer to what is better described as 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 circumstance 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 immersive interfaces.
User interfaces are considered by some authors to be a prime ingredient of Computer user satisfaction.
The design of a user interface affects the amount of effort the user must expend to provide input for the system and to interpret the output of the system, and how much effort it takes to learn how to do this. Usability is the degree to which the design of a particular user interface takes into account the human psychology and physiology of the users, and makes the process of using the system effective, efficient and satisfying.
Usability is mainly a characteristic of the user interface, but is also associated with the functionalities of the product and the process to design it. It describes how well a product can be used for its intended purpose by its target users with efficiency, effectiveness, and satisfaction, also taking into account the requirements from its context of use.
In computer science and human-computer interaction, the user interface (of a computer program) refers to the graphical, textual and auditory information the program presents to the user, and the control sequences (such as keystrokes with the computer keyboard, movements of the computer mouse, and selections with the touchscreen) the user employs to control the program.
Currently (as of 2009) the following types of user interface are the most common:
User interfaces that are common in various fields outside desktop computing:
Other types of user interfaces:
The history of user interfaces can be divided into the following phases according to the dominant type of user interface:
A modality is a path of communication employed by the user interface to carry input and output. Examples of modalities:
The user interface may employ several redundant input modalities and output modalities, allowing the user to choose which ones to use for interaction.
A mode is a distinct method of operation within a computer program, in which the same input can produce different perceived results depending of the state of the computer program. Heavy use of modes often reduces the usability of a user interface, as the user must expend effort to remember current mode states, and switch between mode states as necessary.
A User interface allows a user to interact with a machine. User interfaces mainly provide two things:
Many machines can be very dangerous. A machine should have a user interface that can be handled easily, even if the person operating the machine has panicked. The user interface should therefore be intuitive, and simple to use. An example of such a user interface is that of the kill switch. A kill switch must shut off the machine at all costs - the idea is to avoid injury or harm to people. This is very different from shutting off the machine at the end of the shift, or when it is no longer needed.
According to EN ISO 13850, the kill switch has to be red on a yellow background.
The colors used to mark different states are close to those used by signals used on the road.
|Red||Danger||Alerting of possible danger or of states which make it very important to act immediately|
|Yellow||Something is not normal||If nothing is done, the situation may become dangerous.|
|Blue||Something needs to be done||The person operating the machine needs to do something|
|Green||Everything is normal||Used to show safe conditions, also used to start a new process.|
|While||Neutral||Confirmation, also used for things that cannot be expressed by red, yellow, blue or green.|
|Color||Meaning||What it does||Notes|
|Red||Operate in an emergency||Kill switch, stop, also used for fighting fire||Must not be used for stating/putting the machine into operation|
|Yellow||Something needs to be done to get back to normal||Re-start, Operation to avoid anormal condition or unwanted change.||Must not be used for either starting or stopping a machine.|
|Blue||Start something new||Start, Reset|
|Green||Start the usual/common procedure||Start from a safe state||Must not be used for stopping/switching off|
|White||meaning underermined||Start/On (preferred), Stop/Off|
|Black||Stop/Off (preferred), sometimes Start/On|
There may be additional symbols, for example:
|Symbol||What it does|
In many cases, such symbols are better, because some people are color blind. They need to be explained, like warnings, though.