Int 16 Fn FFCC  U - Pc Tools V5.1-8.0 Desktop - Display Asciz String Cent  [U]

   AX = FFCCh
   DS:SI -> ASCIZ string

Return: AX = ???
   CX = ???
   ES:DI -> address past last character displayed (v5.1/5.5)
         -> ??? on menu bar (v6.0)