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HTG Explains: What Are the Sys Rq, Scroll Lock, and Pause/Break Keys on My Keyboard?

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Glance at your keyboard and chances are you’ll see a few keys you never use near the top-right corner – Sys Rq, Scroll Lock, and Pause / Break. Have you ever wondered what those keys are for?

While these keys have been removed from some computer keyboards today, they’re still a common sight — even on new keyboards.

Image Credit: ajmexico on Flickr

Sys Rq

The SysRq key (sometimes Sys Req) is an abbreviation for System Request. These days, keyboards generally combine the SysRq key with the Print Screen (or Prt Scr) key. To actually invoke the System Request key, you’d need to press Alt+SysRq.

This key was meant for invoking low-level operating system functions. it behaves differently from other keys on your keyboard – when you press this key, your computer’s BIOS generates a special interrupt that tells the operating system the key was pressed. The operating system can listen for the event and do something special.

These days, most operating systems and programs will simply ignore this key-press event. One notable exception is Linux, where the “Magic SysRq key” can send commands directly to the Linux kernel to help recover from crashes and debug the operating system.

sysrq key

Image Credit: solylunafamilia on Flickr

Scroll Lock

Scroll Lock is a toggle, just like Caps Lock and Num Lock – on some keyboards, Scroll Lock may also have a dedicated light.

Scroll Lock was designed for older, text-mode environments, which had a small amount of available screen space. Pressing the arrow keys normally moved the text-entry cursor around, but people wanted a way to scroll up and down through the contents of a text screen.

When Scroll Lock was enabled, the arrow keys would scroll the contents of the screen instead of moving the cursor.

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With modern graphical environments that include scroll bars and mouse wheels, this behavior is no longer necessary – in fact, most programs will ignore the Scroll Lock key entirely.

One notable program that continues to obey Scroll Lock is Microsoft Excel. When Scroll Lock is enabled in Excel, pressing the arrow keys will scroll the viewing area without moving the cursor.

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Pause / Break

The Pause and Break keys were used in DOS and still function in the Command Prompt today.

The Pause key is designed to pause a text-mode program’s output – it still works in the Command Prompt window on Windows. When you press Pause, the output scrolling down your screen will stop. Depending on how the program is written, this may also pause the program’s execution. Press another key after pausing and the program will continue.

The Pause key can also pause many computers during the BIOS boot-up process. This can allow you to read BIOS POST (power-on self-test) messages that flash on your screen for a short time.

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Image Credit: Thiago Avancini on Flickr

The Break key can be used to end DOS applications – pressing Ctrl+Break terminates a DOS application. This shortcut functions similarly to Ctrl+C, which is also used to terminate applications in command-line environments.

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These keys are old and not commonly used – if you wondered who was using them, the answer is very few people. With the exception of the Scroll Lock key in Microsoft Excel, there’s very little the average person can do with these keys. In fact, it’s surprising that they’re still so common on keyboards today.

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.

  • Published 09/26/12

Comments (34)

  1. Dark Reality

    10 cool points to the first (or next?) PC game to implement them, either as a published feature, or as an Easter egg or otherwise hidden feature.

  2. Adrian Martin

    Print Screen + Alt, the SysRq keystroke, captures the active window bitmap to the clipboard.

  3. adam

    Also using Windows Key + Pause|Break will take you to system properties. Pretty handy if you need to get your computer name or if you’re asking someone else for theirs.

  4. Citrus Rain

    In Batman: Arkham Asylum the Scroll Lock key is a full screen/windowed mode toggle.

    Going to add the pause button to my list of tricks now. :)

  5. Terri

    Ctrl-Break is still used in Microsoft Access to stop a query in progress – useful if the query was badly written and it takes ‘forever’ or when de-bugging a query to check for efficiency.

  6. Mark

    So what does the ¬ ` key (top left row next to the 1 key) do?

  7. thegeekkid

    @Mark, that is a character. If you press it in a word processing program, it displays the character. ;)

  8. Torben Schlüntz

    Beside the Pause also at some machines the Ctrl-S does the same trick. I think it is an IBM feature – and still available.

    I do use Break and PrtScr daily.

  9. phil

    SnagIt takes over the PrtSc key so when you use it you get added functionality to your screen caps.

  10. RichardD

    In Windows, I use PrtScr (copy the whole screen to the clipboard) and ALT-PrtScr (copy the active window only to the clipboard) and find them very useful.

  11. Brian

    In Windows 7, WindowsKey + Break brings up the computer properties display

    Also, one of my KVM switches uses a double-press of Scroll Lock to switch between computers

  12. spike

    @Adrian Martin: This isn’t the SysRq key, though.
    My keyboard doesn’t even have a SysRq key :)

  13. spike

    @phil, RichardD: Very interesting, but this article isn’t about Print Screen.

  14. Nissim

    Mark – the ‘¬’ key you mentioned was ‘not’ in the PL/1 language (if I remember correctly). I don’t have it on my keyboard …

  15. istvan

    Thanks for the Windows Key + Pause|Break keystroke !!!!!!

  16. imdb

    SysRq key is the same as your PrtScn key.

  17. Mark

    OK For a shortcut to improved health…Everyone needs to go outside and get some fresh air.

  18. Mike

    I hate to sound like an old fuddy duddy, but they are needed even today and if you know how to use them in the right instances nothing else works.

    “In the old days,” everyone had to learn about them, now not so much. It is like having a small odd tool in your tool kit, for that odd job. Every so often someone says, “What’s that odd tool for?” And when you show them they go “Wow” “I didn’t know you could do that!”

    And after telling them how it is used they often say, “I really could have used that trick when…”

  19. r

    @ Mike : you sound like an old fuddy duddy :P

  20. Jason

    My first x86 machine was in 1989. I used to use the pause, break and print screen keys fairly regularly (especially break, just before Ctrl-Alt-Del and then the power button when things went south) but never SysRq and scroll lock maybe twice just to experiment. This was in MS-DOS 3.3, 4, 5, 6, 6.2 and 6.22. These days I seldom use print screen but still use Windows-Break when using Windows to bring up the system properties dialog quickly.

    I doubt the SysRq key really has a special domain to call a system interrupt. Depending on the BIOS any key or key combination could trigger an interrupt. Ctrl-Alt-Del is probably the most well-known. On my particular machine Ctrl-Alt-Shift-V would toggle the video between CGA or Hercules monochrome (the infamous “green-screen”) modes.

  21. fermier

    re sysrq key

    “The operating system can listen for the event and do something special.”

    never explained what the “special” thing is?

  22. fermier

    Sherlock Holmes would deduce above was written by a grownup.

    Earlier aged person would write “….is??????????”

  23. soloman498

    Scroll lock works to scroll up and down in Firefox when reading Google RSS feeds.

  24. Snap

    when linux crashes I often need the SysRq key combined with R E I S U B and sometimes I use just K (kill).

    (the first comand, will hopefully take controll away from X, write cache to disk, make disk read only, unmount disk, and reboot.)

  25. Saeed Iranzad

    What about “Insert” key? It’s a really useless key.

  26. Daniel

    I hope they don’t get rid of the Sys Req/Print Scr key, otherwise it would be hard to switch between regular view and the High Contrast Black theme I use to make my computer accessible to me on account of my bad eyesight. To do this, I press ALT + SHIFT + PRINT SCR because I sometimes need to see something in the regular default theme.

  27. Qrazydutch

    He Jason … What about dos 6.1? And all the dr dos versions? And IBM dos? And freedos? And babble dos? Dude don’t leave out the ” meat” when discussing the gravy …..

  28. fredneedle

    I use my Scroll Lock key daily to switch my KVM between machines. I double click it then either choose numbers 1 to 4 for whichever machine I want to switch to or I can press the up / down arrow keys to move the KVM through each machine. So much more handy than diving under the desk to press the button on the KVM itself.

  29. Interociter Operator

    If you have the “command prompt” black window up, doing an [Alt][Enter] will blow it up full screen.

    Freaks people out pretty well.

    [Alt][Enter] again returns it to it’s normal size.

  30. Michael

    Excellent, like the windows key + pause/break! Hey, when I used to administrate IBM AS400 a lot, the Sys Req button was to break out of a running process-the AS400 keyboard has this prominently -came in handy!

  31. Ben S

    Gosh WindowsKey+SysRq would have made a lot more sense for the System Property window instead of WindowsKey+Pause. Oh Microsoft…

  32. William Henry

    I created a Macro, when I pressed it empties the waste basket.

  33. Srinivas

    Thanx Chris now i know what this keys actually do

  34. John B

    The ¬ ` key (top left row next to the 1 key)

    Pressed whilst holding the Ctrl key down toggles Function view in Excel.
    Really useful for debuging spreadsheets.

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