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A gauge control in computer programming is a visual component of a user interface. It is designed to display information to a user in an analog style. The control is similar to a true analog gauge that can be seen on the dashboard of a car or in the cockpit of an airplane. The general appearance is that of a circle or other radial dial with an indicator needle on the inside pointing to tick marks on the perimeter; those tick marks indicate a scale of the data being represented. Using a gauge control can help a user to visualize the state of data when there is a minimum and maximum value.
User interface components, also called controls, are the building blocks of graphical user interfaces (GUIs). They can be as simple as a button or as complex as an animated three-dimensional (3D) graph. While many of the components are simple and utilitarian, they also can be designed in a more artistic fashion. Using a gauge control in an interface is a way to display numbers stored digitally in an analog way.
There are many styles of gauge control, most of them modeled from real-world gauges, but all of them acting as a visualization tool. A gauge control is most effective at showing the current state of dynamically changing data in relation to a static minimum and maximum value. As with an actual gauge, a needle move clockwise, pointing toward the edge of the gauge and indicating the value of the variable is increasing. If it moves counterclockwise, it indicates the variable is decreasing. If the needle is positioned at either extreme on the gauge, it shows the variable has reached its minimum or maximum value.
Gauge controls can have different sub-components inside their frame to express even more information in a compact area. A mechanism resembling an odometer-like counter can keep track of non-limited changing numerical data. Smaller dials within the frame of the gauge can display how peripheral data are faring in relation to the main needle.
The use of a gauge control can be purely for aesthetics, as well. Having a series of analog-appearing controls on a virtual dashboard can help to bring a unique sense of style to an otherwise mundane application. In combination with interactive components such as simulated knobs and dials, the entire program can be given the feeling of an actual machine instead of windowed software.