Various widgets. In computer programming, a widget (or control) is an interface element that a computer user interacts with, such as a window or a text box. The defining characteristic of a widget is to provide a single interaction point for the direct manipulation of a given kind of data. Widgets are visual basic building blocks which combined in an application hold all the data processed by the application and the available interactions on this data. A family of common reusable widgets has evolved for holding general information based on the PARC research for the Xerox Alto User Interface. Different implementations of these generic widgets are often packaged together in widget toolkits, which programmers use to build graphical user interfaces (GUIs). Widgets are sometimes qualified as virtual to distinguish them from their physical counterparts, e.g. virtual buttons that can be clicked with a mouse cursor, vs. physical buttons that can be pressed with a finger. A related (but different) concept is the desktop widget, a small specialized GUI application that provides some visual information and/or easy access to frequently used functions such as clocks, calendars, news aggregators, calculators and desktop notes. These kind of widgets are hosted by a widget engine.