[accesscomp] Dan's tip of the day
- From: "Bob Acosta" <boacosta@xxxxxxxxxxx>
- To: "tektalk discussion" <tektalkdiscussion@xxxxxxxxxxxxxxxxxxx>
- Date: Tue, 2 Oct 2012 13:33:11 -0700
What Are the Sys Rq, Scroll Lock, and Pause/ Break Keys on My Keyboard?
By HTG
September 26 2012
http://www.howtogeek.com/latest/260912.html
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.
*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.
*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. 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.
*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.
*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.
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.
on My Keyboard?
By HTG
September 26 2012
http://www.howtogeek.com/latest/260912.html
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.
*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.
*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. 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.
*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.
*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.
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.
Dan Thompson
dthompson5@xxxxxxxxx
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Robert Acosta, President
Helping Hands for the Blind
Email: boacosta@xxxxxxxxxxx
Web Site: www.helpinghands4theblind.org
You can assist Helping Hands for the Blind by donating your used computers to
us. If you have a blind friend in need of a computer, please mail us at the
above address.
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