[fpc-devel] Multithreading under DOS

Michael Schnell mschnell at lumino.de
Fri Sep 27 09:39:15 CEST 2013

On 09/26/2013 02:59 PM, Tomas Hajny wrote:
> ...except when it uses just any RTL function...
ther were lots of "DOS appliances" that could be installed as resident 
add-ons. Same e.g. could handle printer queues as well for the local 
user as for remote network clients in the background. they could show a 
user interface when activated by a hotkey or some other event. So they 
did use disk-IO, keyboard, screen and timer hardware.

The technology used as hooking the appropriate hardware interrupts and 
DOS API functions and after doing their stuff calling the original (or 
previously installed resident appliance).

In fact I remember that at that time I had lots of those running in the 
background of my DOS PC.

Obviously the appropriate issues (such as non-reentant DOS calls) have 
been handled in a perfect way.

I am positive that this could be done by a multithreading aware DOS RTL 
flavor that does user-land reentrand thread scheduling according to the 
original (program.internal only) POSIX specs.

(But of course this is not exactly trivial. :-( )


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