Scroll Lock
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Scroll Lock is a key (with an associated status light) on a computer keyboard. The behavior of the key depends on the particular software in use. In many modern applications, the Scroll Lock key has no assigned function.
The Scroll Lock key is a remnant from the original IBM PC keyboard. In the original design, Scroll Lock was intended to modify the behavior of the arrow keys. When the scroll lock mode was on, the arrow keys would scroll the contents of a text window. In this sense, Scroll Lock serves a similar purpose to Num Lock and Caps Lock: it enables a secondary function of a group of keys. Today, this particular use of Scroll Lock is rare. Only a few modern programs still honour this behavior, such as Microsoft Excel (in the behaviour of arrows — when Scroll Lock is on the selection does not move) and Lotus Notes. In modern GUI environments, scrolling is usually accomplished using other means such as scrollbars.
In Linux command line sessions, the Scroll Lock key is used to pause screen output. This behavior emulates the Hold Screen key or similar flow control mechanisms on computer terminals. Because of this emulation, the term scroll lock is sometimes used to generically refer to a screen pausing behavior. This usage could potentially cause confusion since screen pausing behavior is not intrinsically a part of the Scroll Lock key. In DOS, the Pause key pauses the screen output.
In FreeBSD and other BSD descendants Scroll Lock still functions similarly to IBM's original design.