🚀 go-pugleaf

Is the undocumented Swappable Data Area implemented in DOS 5.0, and
is it compatible with the SDA's of DOS 3.30 or DOS 4.01?

I have read the book Undocumented DOS by Schulman et al, but the sample
TSRs on the disk that used the SDA, worked only if I fooled them to
beleive my DOS version was 3.30.  Even then they seemed a bit unstable.

The SDA is used to implement task switching, even in the middle of a
DOS interrupt 21h call.

I use 4DOS 4.01 with DOS 5.0, but as the SDA can hardly be implemented
in COMMAND.COM, I can see no reason why 4DOS should be a problem.

I would appreciate it if any of the authors of the book, Ralph Brown
for example, would answer me on this.  Although all of you netters 
are most welcome, of course... :)


robert@solan.unit.no