Thursday, 10 July 2008

The 3 mistakes on my keyboard

Ever wondered what the SysRq, Scroll Lk and Break keys near the top right corner are for and if they do serve any purpose at all? The simple answer is they are indeed obsolete. They however continue to remain on the keyboard because keyboard manufactures never saw the need to vacate these veteran keyboard tenants. Some of the keyboards today however have done away with them. But why are they there in the first case are you wondering? Here's why.

Sys Rq: Initially designed as a software interrupt which could bypass the OS and directly interact with the BIOS (the origins can be traced to the antique IBM 3270 machines) to facilitate multi-tasking, the interrupt was left largely unutilized by subsequent operating systems . Keyboards today don't even write anything to the keyboard buffer when this key is pressed. So it should not be long before Print Screen has the whole key all to itself!

Scroll Lk: The scroll lock was introduced in the early days of computing when the screen was limited to 25 rows of 80 character each. As you can imagine, it would have served as a modifier key (akin to Shift and Ctrl) for the arrow keys letting you either move along a line of text or scroll through screen-full of insipid text. Surprisingly however, MS Excel still supports its functionality by locking the cursor to the current cell when you use the arrow keys with the scroll lock turned on. [That should somehow make up for the lack lustre performance, huh!]. According to sources on the net the scroll lock purportedly prevents text from scrolling in command line sessions in Linux. [At least it didn't work when I tried it on the command line in Solaris]

Break: As against its other two neighbours, the break key still retains it uses, but the utility of its fellow occupant, Pause is dubious. Its origin can be traced back to the days of telegraphic communication when a constantly ON line meant the line was up and working and any break (or pause) in line acted as an interrupt notifying the operator at the receiving end of an impending transmission (or in rare cases, a break/fault in the line). While Ctrl+Break halts the execution of many a compilers like TC, Pause is just as wasted as its other two neighbours with its use limited to DOS. But hey! One cool thing is Windows+Break brings up the system properties in Windoze!


mtg said...

I'd like to point out that SysRq is used in linux as part of a magic key combination to rescue a crashed system (probably something most people don't encounter, thus, never need to see :-)) ( Also, while break is rarely used (save for using ctrl-break to break infinite while loops), pause retains it's use and is bound to the pause function in many relevant applications (games, for instance). It's true that most environments ignore the scroll lock key, though. I've never had to use that one!

Nithin "Kitta" Shenoy said...

I had never even bothered why these keys existed! Good one..