= MVC

Model View Controller, or MVC in short, is a software design pattern used to develop [https://en.wikipedia.org/wiki/Graphical_user_interface GUI]s.

The details of the approach are explained well on the [https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller MVC wiki page]. In short, 
* A model contains the data that the user is adjusting. 
* A view shows the data in a GUI to the user (eg, graph, text field, slider position)
* A controller allows the user to change the data (eg dragging sliders, entering text or numbers, clicking check boxes)

A view and controller can, and often are, merged into a single component. For example a slider shows the current value, but the user can also drag the slider; or a checkbox shows the current setting (on or off) while the user can simply click on it to toggle the value.