SL> Could a program remain resident without using int27 and int21/31?
They all do -
   while they're running.
It could start another dos shell (by exec-ing %comspec%) but I guess that's
not what you want.
Otherwise maybe it could somehow "figure out" the address that int 27 or 
1/21
leads to in the kernal and do a far jump, but it would be hard to make that
portable.
Have you got a particular application in mind?.
                        
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