View source for Scroll Lock

{{short description|Computer key}}
{{Use dmy dates|date=July 2019|cs1-dates=y}}
{{Use list-defined references|date=August 2022}}
[[File:Scroll-lock.jpg|thumb|The scroll-lock key with an activated indicator light on an [[Model M Keyboard|IBM Model M keyboard]].]]
'''Scroll Lock''' or '''ScrLk'''<ref>{{cite web |title=Turn off Scroll Lock - Microsoft Support |url=https://support.microsoft.com/en-us/office/turn-off-scroll-lock-a78492cc-c124-4782-a38b-df46669520e0 |website=support.microsoft.com}}</ref> (sometimes notated '''⤓'''<ref>Graphic is seen enclosed in rounded rectangle on scroll lock key in photograph in {{cite web |title=What Is Scroll Lock Key? [How to Turn It Off] - Alvaro Trigo's Blog |url=https://alvarotrigo.com/blog/scroll-lock-key/ |date=16 April 2022}}</ref> or '''↕'''<ref>Graphic is seen enclosed in rounded rectangle on scroll lock key in photograph in {{cite web |last1=Makvana |first1=Mahesh |title=How to Turn Scroll Lock Off (or On) in Microsoft Excel |url=https://www.howtogeek.com/816699/how-to-turn-off-scroll-lock-in-excel/ |website=How-To Geek |language=en |date=13 August 2022}}</ref>) is a [[lock key]] (typically with an associated status light) on most [[IBM]]-compatible [[Keyboard (computing)|computer keyboard]]s. Depending on the operating system, it may be used for different purposes, and applications may assign functions to the key or change their behavior depending on its toggling state.<ref name="IBM_Owners_Manual"/><ref name="IBM_1983_PC-TR"/> The key is not frequently used, and therefore some reduced or specialized keyboards lack {{keypress|Scroll Lock}} altogether.

Pressing {{keypress|Ctrl|Scroll Lock}} performs the same function as pressing {{keypress|Ctrl|Pause/Break}}. This behavior is a remnant of the original [[IBM PC keyboard]]s, which did not have a dedicated [[Break (Pause)|{{keypress|Pause/Break}}]] key. Instead, they assigned the Pause function to {{keypress|Ctrl|Num Lock}} and the Break function to {{keypress|Ctrl|Scroll Lock}}.

==Function==
===Window scrolling===
The {{keypress|Scroll Lock}} key is meant to lock all scrolling techniques and is a vestige of the original [[IBM PC keyboard]]. In its original design, {{keypress|Scroll Lock}} was intended to modify the behavior of the [[arrow keys]]. When the {{keypress|Scroll Lock}} mode is on, the arrow keys [[scrolling|scroll]] the contents of a text window instead of moving the [[Cursor (computers)|cursor]].<ref name="IBM_Owners_Manual"/><ref name="IBM_1983_PC-TR"/> In this usage, {{keypress|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 {{keypress|Scroll Lock}} is rare. Modern programs honoring this behavior include [[Microsoft Excel]], [[Microsoft Project]],<ref name="Microsoft_Project"/> [[FL Studio|Image-Line FL Studio]],<ref>{{Cite web |title=Toolbar |url=https://www.image-line.com/fl-studio-learning/fl-studio-online-manual/html/toolbar_panels.htm |access-date=2023-09-08 |website=www.image-line.com}}</ref> [[IBM Lotus Notes]], [[Forté Agent]], [[Renoise]], [[Cakewalk by BandLab]], and [[LibreOffice Calc]].

Some text editors (such as [[Notepad++]], [[Microsoft Visual Studio]]) exhibit similar behavior when the arrow keys are used with [[Control key|{{keypress|Ctrl}}]] pressed.

Most [[Graphical user interface|GUI]] environments neglect {{keypress|Scroll Lock}}, which means scrolling must be accomplished with a [[computer mouse|mouse]], using means such as [[scrollbar]]s or [[scroll wheel]]s, or an "autoscroll" feature activated by the middle mouse button (which may be part of the scroll wheel). In some instances, {{keypress|Ctrl}}+{{keypress|Shift}} in conjunction with the arrow keys can enable scrolling.

Some web browsers including [[Google Chrome]], [[Firefox]], and [[Internet Explorer]] support a [[caret browsing]] mode which can be toggled by {{keypress|F7}}. While the window scrolling behavior with caret navigation disabled (the default) is similar to that suggested for Scroll Lock, enabling caret navigation will enable a cursor scrolling behavior as if Scroll Lock were disabled.

===Console scrolling===
Pressing the {{keypress|Scroll Lock}} key in the [[Linux console]] while the text is scrolling through the screen freezes the console output (but not input) during which no further text is sent to the screen, while the program continues running as usual — or becomes blocked at the {{mono|write}} [[syscall]] when too much data is prevented from reaching the terminal, causing the tty's output queue to become full if the tty file descriptor is not using non-blocking I/O. When {{keypress|Scroll Lock}} is pressed again, the screen is unfrozen and all text generated during the freeze is displayed at once and the program continues to run normally. This allows the user to pause the display and read long log messages that scroll through the screen too quickly to read, such as when the system is [[booting up]] (provided the keyboard [[Device driver|driver]] has already been loaded). Unless configured otherwise or in raw mode, {{keypress|Ctrl|S}} (DC3 in ASCII) and {{keypress|Ctrl|Q}} (DC1 in ASCII) can be used instead of Scroll Lock in Unix-like systems to freeze and unfreeze the tty output respectively.

This behavior emulates the Hold Screen key or similar flow control mechanisms on computer terminal hardware.

On the [[FreeBSD]] system console, the {{keypress|Scroll Lock}} key not only pauses output, but additionally enables scrolling: after pressing {{keypress|Scroll Lock}}, one can use {{keypress|Page Up}} and {{keypress|Page Down}} to scroll up or down. Pressing {{keypress|Scroll Lock}} again disables this mode and moves back to the bottom of the output. The Linux console implemented this behaviour by using {{keypress|Shift|Page Up}} and {{keypress|Shift|Page Down}}, not requiring {{keypress|Scroll Lock}} to be active; this behavior has been removed due to a vulnerability (CVE-2020-14390).<ref>{{Cite web |title=Linux 5.9 Dropping Soft Scrollback Support From FB + VGA Console Code |url=https://www.phoronix.com/news/Linux-5.9-Drops-Soft-Scrollback |access-date=2022-12-22 |website=www.phoronix.com |language=en}}</ref> The [[NetBSD]] console can be scrolled either with {{keypress|Shift|Page Up}}/ {{keypress|Shift|Page Down}} or by pressing {{keypress|Scroll Lock}} then {{keypress|Page Up}}/{{keypress|Page Down}} .

===Boot diagnostics===
In [[Multiuser DOS]], [[Datapac System Manager|System Manager]], and [[REAL/32]], activating {{keypress|Scroll Lock}} during boot will always enter a special diagnostic mode, where the operating system and loaded device drivers will display detailed status and debugging information about themselves and their interaction with the operating system, sometimes up to several screenfulls per loaded driver.<ref name="Paul_1997_OD-A3"/> Automatic scrolling is suspended for as long as {{keypress|Scroll Lock}} remains activated.<ref name="CCI_1997_HELP"/>

[[DR-DOS 7.02]] and higher provides a [[CONFIG.SYS]] directive named <code>[[SCROLLOCK (CONFIG.SYS directive)|SCROLLOCK]]=ON|OFF</code> to change the Scroll Lock status on the fly.<ref name="Paul_1997_OD-A3"/> Activating {{keypress|Scroll Lock}} during boot will enter a DIAG mode as well, wherein some special drivers may display more verbose messages,<ref name="Paul_1997_OD-A3"/> but in contrast to the situation under the Multiuser DOS family normal DOS drivers do not typically display additional information. The operating system, however, will temporarily suspend any automatic timeouts (<code>[[TIMEOUT (CONFIG.SYS directive)|TIMEOUT]]=<nowiki><seconds>,<character>,<switch></nowiki></code>) in CONFIG.SYS trace (<code>[[TRACE (CONFIG.SYS directive)|TRACE]]=ON|OFF</code>) and {{keypress|F7}}/{{keypress|F8}} single-stepping modes for as long as {{keypress|Scroll Lock}} is active.<ref name="Paul_1997_OD-A3"/>

===Debugging===
In the [[Microsoft Windows NT]] family starting with Windows 2000, a debugging feature can be enabled, that allows the user to manually crash the system, generating a memory dump for analysis of the current state of the operating system. This can be accomplished by setting the REG_DWORD registry key <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parameters\CrashOnCtrlScroll</code> to <code>1</code>. Once set, the user can hold the {{keypress|RCtrl}} key and tap the {{keypress|Scroll Lock}} key twice to trigger a [[Blue Screen of Death]].<ref name="Microsoft_KB233139"/><ref name="Dialy_2000_Tricks"/>

In [[Microsoft Visual Basic 5.0]] and [[Microsoft Visual Basic 6.0|6.0]], {{keypress|Ctrl|Pause/Break}} pauses the running program in the integrated development environment, as does its alias {{keypress|Ctrl|Scroll Lock}}.

==={{anchor|CC}}Copy and paste===
In conjunction with the alternative DOS keyboard and console drivers FreeKEYB and K3PLUS, {{keypress|Scroll Lock}} also serves as part of a [[copy & paste]] facility between applications. Compared to the standard keyboard driver [[KEYB (DOS command)|KEYB]] these drivers offer several extensions including an [[extended keyboard buffer|extended keystroke buffer]] with key stacking facility, macro recorder, and a second cursor called CopyCursor, which can be invoked on demand (by default on pressing {{keypress|Ctrl|Alt|F11}} or the middle mouse button) and freely move on the screen using the cursor keys or the mouse, even outside the area reachable by the standard cursor in the running application. Once invoked, pressing {{keypress|F11}} (or the left mouse button) the characters under the CopyCursor can be stuffed, one after another, into the keyboard buffer, from where they will be read by the running application as emulated key (or [[Alt Numpad]]) input, thereby typically showing up at the location of the standard cursor. The CopyCursor will move to the next screen position after each {{keypress|F11}} (or backwards with each {{keypress|Shift|F11}}). Normal keyboard input is possible while the CopyCursor is enabled, and the user can switch between the two cursors by toggling the {{keypress|Ctrl|Alt|F11}} hotkey again. Pressing {{keypress|Esc}}<!-- ignoring the ESC as input --> or {{keypress|Enter}}<!-- taking the Enter as normal input at the same time --> exits the CopyCursor, so that, on its next invocation, it will show up at the position of the standard cursor again rather than at its previous location. If the screen contents are scrolled, the position of the CopyCursor will move accordingly until reaching the display limits. With {{keypress|Scroll Lock}} activated, keypresses will still reach the normal keystroke buffer, while CopyCursor input will be stacked up internally for later use in a second queue, dynamically maintained within the extended keystroke buffer. Thereby, it is possible to "collect" selected screen output from different programs and spool out the data much later while within yet another application by toggling {{keypress|Scroll Lock}} off again. It is also possible to use this as input into the macro recorder for later use as [[scrap macro]]. Since this is an integral part of these keyboard drivers, it is fully transparent to running software and therefore works with virtually any DOS program, including at the command prompt, temporary shelled programs, and task switchers.<ref name=" Paul_1995_K3PLUS"/><ref name="Paul_1997_FreeKEYB"/><ref name=" Paul_2006_FreeKEYB"/>

===Other uses===
[[IBM PC]] documentation called {{keypress|Scroll Lock}} an "inactive key". When ''[[PC Magazine]]'' asked an executive of keyboard manufacturer [[Key Tronic]] about the key's purpose in a 1983 interview, he replied "I don't know, but we put it on ours, too."<ref name="sandler198301"/>

The indicator light is sometimes used for other purposes such as a [[keyboard layout]] indicator<ref name="Ubuntu"/><ref name="Gnome"/> in some [[Linux distributions]] or other applications,<ref name="Keyboard_illuminator"/> because doing so is less likely to cause problems than manipulating other keys/lights.

[[KVM switch|Keyboard, video, mouse switches]] (KVM) often use the Scroll Lock key on the keyboard connected to the KVM switch for selecting between computers. On KVM switches with [[On-screen display]] (OSD), a "double click" of the Scroll Lock key often brings up the OSD, allowing the user to select the desired computer from a list or access the configuration menu of the KVM. Some models, especially those without an OSD, switch to the input corresponding to the number key pressed after Scroll Lock, or in the case of some two-port switches, the up and down arrow keys. Simple models with only two or four inputs may immediately switch to the next input following a double press of the Scroll Lock key.
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* In [[FL Studio]], the Scroll Lock key, when on, will prevent the screen from scrolling when the time marker moves out of the visible area.
* On some [[Dell]] [[laptop]]s the Scroll Lock key becomes the [[Fn key]] when an external keyboard is used. This behavior can be disabled in the [[BIOS]].
* In most 'LED light' Mods for keyboards, to give the keyboard an overhead LED so the keyboard can be lit up, the Scroll lock key is used to switch it On and Off and the LED light is unsoldered and a new brighter LED is attached overhead the keyboard.
* In the [[Opera (web browser)|Opera]] [[web browser]] the Scroll Lock key is utilized to toggle "listening mode" for the browser's built-in [[Speaker recognition|voice recognition]] feature.
* In [[Synergy (software)|Synergy]], the Scroll Lock key is utilized to lock the use of mouse and keyboard functions to a specific PC.
* In [[Stepmania]], pressing the Scroll Lock key opens the Options menu.
* In the multilingual text editor [[iLeap]], the Scroll Lock key is used as a toggle switch to change between two languages.
* [[X Window System]] can be configured to indicate changing to an alternative keyboard layout by turning on the Scroll Lock light.
* In [[FreeBSD]], and other [[Berkeley Software Distribution|BSD]] descendants, Scroll Lock still functions similarly to [[IBM]]'s original design.
* Individual applications may assign any function to this key as an added convenience [[keyboard shortcut|hotkey]].
* [[Xfire]], a chat application for use while playing a video game, is activated by using the default key combination of "Scroll Lock" + "X". Xfire also uses Scroll Lock for other in-game purposes, such as taking screenshots. Sometimes its [[Light-emitting diode|LED]] is used to notify users that an event occurred.
* In the media system [[My media system|My Media System]], navigation is done in a fashion very similar to the original idea of the Scroll Lock key. At the beginning and end of a list, navigating will move the cursor but not the view. In the middle of the list, the cursor will be locked in the middle of the screen while the view moves.
* [[Konsole]], a [[terminal emulator]] for [[KDE]] uses the Scroll Lock key to make the arrow keys scroll back the buffer, rather than going up and down in the command history (the default behavior of the arrow keys in Konsole). This has often led to problems while using the [[Xine]] media player, as Xine emits a Scroll Lock key signal to prevent the screensaver from starting. This will in turn make Konsole switch the arrow key behavior. {{Citation needed|date=November 2008}}
* [[Maplestory]], an online [[MMORPG]], utilizes the Scroll Lock key to take pictures, ignoring its toggling function (that is, it does not matter if the Scroll Lock LED is on or off).
* [[Combat Arms (video game)|Combat Arms]], a [[free-to-play]] [[microtransaction]]-based [[first-person shooter]], uses the Scroll Lock key to lock the movement of chat messages.
* [[TeamViewer]], a program that allows users to watch and control another person's screen for use of technical support, uses the Scroll Lock key when viewing to send hotkeys directly to the person being viewed/controlled instead of the viewer's computer. For example, if the user wants to open task manager using CTRL+ALT+DEL on the computer or another user at that time, the scroll lock should be turned on.
* Many programs (e.g. e-mail clients) will toggle the Scroll Lock and in the process flash the [[LED]] on and off to alert the user's attention.
* [[Winamp]] uses scroll lock in its main visualizer, [[MilkDrop]]. When pressed, the visualizer preset is then locked and will not change until the scroll lock is pressed again.
* The N64 Virtual Pad controller plugin for [[Project64]] and [[1964 (emulator)]] was the first to emulate the [[Nintendo 64 Rumble Pack]], which it does so by flashing the Scroll Lock LED.
-->

==Scroll Lock on keyboards without a Scroll Lock key==
Laptops and keyboards without a physical {{keypress|Scroll Lock}} key<ref name="Logitech"/> may have a second function on another key that acts as if a {{keypress|Scroll Lock}} key is activated. 

Some common methods are:
* {{keypress|Fn|S}} or {{keypress|Fn|F6}} on certain Dell laptops.<ref name="Dell"/>
* {{keypress|Fn|C}} or {{keypress|Fn|K}} on certain Lenovo laptops.
* {{keypress|Fn|C}} on certain HP laptops.<!-- Needs more examples. [[List of laptop brands and manufacturers]] has a list. -->
* {{keypress|Fn|F11}} on Windows.

Another way to press {{keypress|Scroll Lock}} is to use an on-screen keyboard. In Windows 8 and later versions, it can be found in the "Windows Ease of Access" program group. This will provide access to an emulation of a standard 101/102-key keyboard.<ref name="Microsoft_Windows-8"/>

==See also==
* [[Arrow keys]]
* [[Break key]]
* [[Scroll wheel]]
* [[Sys Rq]]

==References==
{{reflist|refs=
<ref name="IBM_Owners_Manual">IBM: ''IBM PC User Manual''. Page 5-20: "This key is interpreted by appropriate application programs as indicating that the use of the cursor-control keys should cause windowing over the text rather than cursor movement. Pressing the Scroll Lock key a second time reverses the action. The keyboard routine simply records the current shift state of the Scroll Lock key. It is the responsibility of the system or application program to perform the function."</ref>
<ref name="IBM_1983_PC-TR">{{Cite book |title=IBM Personal Computer Technical Reference |publisher=[[IBM Corporation]] |edition=Revised |date=March 1983 <!-- |id=6172234 NB. This is the IBM number of the German issue of the book "IBM Personalcomputer Technisches Handbuch", also a revised edition from 1983, therefore left commented out for now. Not sure when exactly the original version was published. -->}}</ref>
<ref name="Paul_1997_OD-A3">{{cite web |author-first=Matthias R. |author-last=Paul |title=Caldera OpenDOS 7.01/7.02 Update Alpha 3 IBMBIO.COM README.TXT |url=http://www.uni-bonn.de/~uzs180/download/ibmbioa3.zip |date=1997-10-02 |access-date=2009-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20031004074600/http://www-student.informatik.uni-bonn.de/~frinke/ibmbioa3.zip |archive-date=2003-10-04}} [https://web.archive.org/web/20181225154705/http://mirror.macintosharchive.org/max1zzz.co.uk/+Windows%20&%20DOS/DOS/System/Novell/Support/Bins/Op702src.zip<!-- Op702src.zip is an unofficial renamed distribution of the ibmbioa3.zip file -->]</ref>
<ref name="Microsoft_KB233139">{{cite web |url=http://support.microsoft.com/kb/244139 |title=Windows feature lets you generate a memory dump file using the keyboard |access-date=2011-09-25 |publisher=[[Microsoft Corporation]]}}</ref>
<ref name="Dialy_2000_Tricks">{{cite web |url=https://technet.microsoft.com/library/cc722915.aspx |title=Sean Daily, Tricks & Traps: Daily Answers |date=November 2000}}</ref>
<ref name="Paul_1995_K3PLUS">{{citation |title=K3PLUS v6 - Der ultimative Ersatz für den DOS-Standard-Tastaturtreiber KEYB GR |language=de |edition=r49-v6.21 |author-first1=Axel C. |author-last1=Frinke |author-first2=Matthias R. |author-last2=Paul |type=User Manual |date=1995-05-10 |orig-date=1991}} (NB. K3PLUS was an extended keyboard driver for DOS widely distributed in Germany at its time, with adaptations to a handful of other European languages available. It did support a sub-set of the FreeKEYB features already. <code>K3PLUS.DOC</code> is part of the <code>K3P621P2.ZIP</code> distribution package.)</ref>
<ref name="Paul_1997_FreeKEYB">{{citation |title=FreeKEYB - Enhanced DOS keyboard and console driver |edition=v6.5 |author-first1=Matthias R. |author-last1=Paul |author-first2=Axel C. |author-last2=Frinke |type=User Manual |date=1997-10-13 |orig-date=1991}} [https://web.archive.org/web/20190309194320/http://sta.c64.org/dosprg/fk657p1.zip<!-- FreeKEYB 6.57p1 Beta as of 2004-08-17 with outdated and incomplete documentation -->] (NB. FreeKEYB is a [[Unicode]]-based dynamically configurable successor of K3PLUS supporting most [[keyboard layout]]s, [[code page]]s, and [[List of country calling codes|country code]]s.)</ref>
<ref name="Paul_2006_FreeKEYB">{{citation |title=FreeKEYB - Advanced international DOS keyboard and console driver |edition=v7 preliminary |author-first1=Matthias R. |author-last1=Paul |author-first2=Axel C. |author-last2=Frinke |type=User Manual |date=2006-01-16}}</ref>
<ref name="sandler198301">{{cite journal |author-first=Corey |author-last=Sandler |title=Key Tronic's Soft Touch |journal=[[PC Magazine]] <!-- To be verified: | volume=2 | series=1 --> |date=January 1983 |pages=347 |url=https://books.google.com/books?id=vy3cBZkjbZgC&pg=RA3-PA347 |access-date=2013-10-21}}</ref>
<ref name="Ubuntu">[http://uc.exteenblog.com/padcharee/images/12/11.JPG 11.JPG] (การใช้งาน Ubuntu | SAMUTSAKHON FOUNDATION)</ref>
<ref name="Gnome">{{cite web |url=http://library.gnome.org/users/user-guide/2.32/prefs-keyboard.html.en#prefs-keyboard-layoutoptions |title=Keyboard Layout Options, Keyboard Preferences |work=Desktop User Guide - GNOME Library}}</ref>
<ref name="Keyboard_illuminator">{{cite web |url=http://www.instructables.com/id/Illuminated-Keyboard-Hack/ |title=Illuminated Keyboard Hack |access-date=2011-07-25 |quote=Using the Scroll Lock key for illuminating your keyboard |publisher=Kipkay (via Instructables) |date=2008-05-30}}</ref>
<ref name="Logitech">{{cite web |url=http://forums.logitech.com/logitech/board/message?board.id=general&message.id=11846#M11846 |title=Keyboard&nbsp;— General Discussion |access-date=2008-11-26 |quote=This keyboard does not have a Scroll Lock key |publisher=[[Logitech]] |date=2008-08-28}}</ref>
<ref name="Microsoft_Windows-8">{{cite web |url=http://windows.microsoft.com/en-AU/windows-8/type-with-the-on-screen-keyboard |title=Use the On-Screen Keyboard (OSK) to type}}</ref>
<ref name="CCI_1997_HELP">{{cite book |title=CCI Multiuser DOS 7.22 GOLD Online Documentation |id=HELP.HLP |date=1997-02-10 |publisher=[[Concurrent Controls, Inc.]] (CCI)}}</ref>
<ref name="Microsoft_Project">{{cite web |url=https://support.office.com/en-us/article/Accessibility-in-Microsoft-Project-079E2132-7AD5-4FC5-B9F7-DEE08F728730 |title=Accessibility limitations in Project |website=www.Microsoft.com}}</ref>
<ref name="Dell">{{cite web |url=http://cdn.cnetcontent.com/0b/87/0b875d86-4bdc-4b39-a6a0-fe922d9b71a1.pdf#page=18 |title=Dell Inspiron 17 specification}}</ref> 
}}

==External links==
* {{URL|https://www.straightdope.com/21343263/what-s-the-scroll-lock-key-on-my-computer-for|What's the "Scroll Lock" key on my computer for?}}

{{Keyboard}}
{{keyboard keys}}

{{DEFAULTSORT:Scroll Lock}}
[[Category:User interface techniques]]
[[Category:Lock keys]]
[[Category:IBM PC compatibles]]