[fpc-pascal] Pause Key

Nikolay Nikolov nickysn at gmail.com
Sat Apr 15 13:23:12 CEST 2023

On 4/14/23 20:38, Virgo Pärna via fpc-pascal wrote:
> On Thu, 13 Apr 2023 20:53:09 -0400, Travis Siegel via fpc-pascal <fpc-pascal at lists.freepascal.org> wrote:
>> I know of no way to obtain the pause key status under windows.  I can
> 	Considering, that only Caps Lock, Scroll Lock and Num Lock keys
> have status lights on keyboard I would suspect, that there is not such
> thing as Pause status on PC keyboard.

There is such a thing under DOS, because the BIOS treats the Pause key 
in a special way. When you press it, the BIOS enters a loop and stops 
execution of your program, until you press Pause again. This is done, so 
that you can pause the output to the console, in case it is scrolling 
too fast, so that you can examine it. For this purpose, there's a flag 
in the BIOS data area, which is documented here:


Bit 3 (mask 08h) at 0040h:0018h contains the Pause status. However, I 
don't think there's such an equivalent under Windows and Linux. 
Actually, the Linux console (but not X11!) uses Scroll Lock to pause the 
console output, pretty much the same way DOS and BIOS used the Pause 
key. Why didn't Linus Torvalds use the Pause key is beyond me.


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