Scroll Lock

Scroll lock is an antiquated keyboard button (often with an associated status light) on some computer keyboards. The key is not frequently used and therefore some keyboards lack Scroll Lock altogether.

The Scroll Lock key was meant to lock all scrolling techniques, and is a remnant from the original IBM PC keyboard, though it is not used by most modern-day software. 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 instead of moving the cursor. In this usage, Scroll Lock is a toggling lock key like Num Lock or Caps Lock, which have a state that persists after the key is released.

Today, this particular use of Scroll Lock is rare. Only a few modern programs still honor this behavior, such as Lotus Notes, and Microsoft Excel. Most GUI environments neglect Scroll Lock, which means scrolling must be accomplished with a computer mouse, using means such as scrollbars or scroll wheels. Some text editors (notably, Visual Studio) exhibit similar behaviour when arrow keys are used with control key depressed.

Other uses

Because the key is otherwise rarely used, programs that tie into other software often use it to prevent issues arising from both programs using the same key.

The indicator light is also sometimes used in certain applications, as well as Keyboard Layout Indicator in some Linux distributions (like Ubuntu) because doing so is less likely to cause problems than manipulating other keys/lights.

In Microsoft Windows 2000 and later, a registry setting can be changed to enable a debugging feature that allows the user to manually crash the system, generating a memory dump for analysis. Once set, the user can hold the Ctrl key and tap the Scroll Lock key twice to trigger a BSOD.

See also

• System request
• Pause/Break Key
• AltGr key

External links

• Straightdope article about the Scroll Lock key

IBM PC keyboard (Windows, ANSI US layout)
Esc		F1	F2	F3	F4		F5	F6	F7	F8		F9	F10	F11	F12		PrtScn/ SysRq	Scroll Lock	Pause/ Break
																	Insert	Home	PgUp		Num Lock	∕	∗	−
																	Delete	End	PgDn		7	8	9	+
																					4	5	6
																		↑			1	2	3	Enter
																	←	↓	→		0    Ins		.  Del