Scrollbar
A scrollbar is a graphical control element with which continuous text, pictures or anything else can be scrolled including time in video applications, i.e., viewed even if it does not fit into the space in a computer display, window, or viewport. It was also known as a handle in the very first GUIs.
Scrollbars are present in a wide range of electronic devices including computers, graphing calculators, mobile phones, and portable media players. They usually appear on one or two sides of the viewing area as long rectangular areas containing a bar (or thumb) that can be dragged along a trough (or track) to move the body of the document as well as two arrows on either end for precise adjustments. The "thumb" has different names in different environments: on the Macintosh it is called a "scroller"; on the Java platform it is called "thumb" or "knob"; Microsoft's .NET documentation refers to it as "scroll box" or "scroll thumb"; in other environments it is called "elevator", "quint", "puck", "wiper" or "grip". Additional functions may be found, such as zooming in/out or various application-specific tools. Depending on the graphical user interface, the size of the thumb can be fixed or variable in size; in the later case of proportional thumbs, its length would indicate the size of the window in relation to the size of the whole document. While proportional thumbs were available in several GUIs, including GEM, AmigaOS and PC/GEOS, even in the early 1980s, Microsoft did not implement them until Windows 95. A proportional thumb that completely fills the trough indicates that the entire document is being viewed, at which point the scrollbar may temporarily become hidden. The proportional thumb can also sometimes be adjusted by dragging its ends. In this case it would adjust both the position and the zooming of the document, where the size of the thumb represents the degree of zooming applied.