INT 2fH 4BxxH: Task Switcher Functions

                                                         Compatibility: 3.0+ 
     See: Switcher API Overview for background info.

          4b01H (build notification chain)

          4b02H (is switcher installed? / get service addr)

          4b03H (allocate switcher ID)

          4b04H (free switcher ID)

          4b05H (identify instance data)

          Switcher Services and Notifications (interact with the switcher)

 These functions are used by application programs, especially TSRs, which
 have special needs with regard to task switching; for instance, programs
 which must prevent the DOS Shell from swapping them out or switching to
 another program (say, via Alt+Tab).  They also enable a TSR to maintain
 instance data--a unique data area for each DOS session.

See Also: INT 2fH: Multiplex Interrupt
          DOS Functions