[Coco] DECB DOS Command

[jdaggett at gate.net]

The SWI3 vector was often used in debugging code. A method of 
inserting breakpoints. It could have been there from developemnt 
days and never removed. The SWI2 and 3 do an entire stack but 
only effect teh E bit of the CCR. . 


james

On 13 Dec 2003 at 20:13, Arthur Flexser wrote:

> But, wouldn't it have been simpler to just have that application set
> up its own warm start address, in place of having to set up the SWI3
> vector with that address?  Where's the gain in using SWI3?
> 
> Art
> 
> On Sat, 13 Dec 2003, John E. Malmberg wrote:
> 
> > tim lindner wrote:
> > > I was just reading the Disk BASIC unravelled book and came away
> > > with the following question:
> > > 
> > > Why does the 'DOS' command first issue a SWI3 instruction?
> > > 
> > > Disk BASIC sets up the SWI3 vector to do nothing. It just returns
> > > to the caller. 
> > 
> > Well I do not know what it was intended for, but when I know of
> > several things that it could be used for.
> > 
> > While it may be difficult to get ROM BASIC to work under OS-9, it is
> > relatively trivial to get it to work under FLEX+.
> > 
> > The major issue when doing that is that to exit back to FLEX, you
> > had to EXEC back to the right location.  The DOS command would allow
> > a warm start.
> > 
> > So this feature can be very useful, if you want to use the DOS
> > command to load something other than OS-9 that can run DECB, and
> > wants to do a warm start.
> > 
> > -John
> > wb8tyw at qsl.network
> > Personal Opinion Only
> > 
> > 
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> > 
> 
> 
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