Int 2F Fn DA55  U - Trap.com - Installation Check                          [G]

   AX = DA55h
   DL = interrupt number
   DH = ???

Return: if installed
       AH = interrupt number
       AL = ???
       ES:BX -> ???
Program: TRAP is an interrupt call tracer by Patrick Phillipot/Udo Chrosziel

Note:  a separate copy of TRAP is loaded for each interrupt to be traced; thus
     the interrupt number is part of the installation check