+0 4 pfrNext address of next SwCallbackInfoRec in the
notification chain (or 0000:0000 if last entry)
+4 4 pfHandler addr of notification-function handler
16 size of an SwCallbackInfoRec structure
pfrNext this is the address of the next SwCallbackInfoRec in the
(build notification chain).
pfHandler the FAR address of the code that will be called for various
pfarAPIs the FAR address of the first of a series of SwApiInfoRec
structures that identify how much support this program
provides for various asynchronous request APIs. The list ends
when the first field of that structure is 0000H.
This structure is used in SwSrvcFn 0004H (hook notification chain) and in
INT 2fH 4b01H (build notification chain). It is part of the system that
allows programs to be notified when they are about to be switched out or
that they can resume operation, etc.