INT 21 U - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE
AX = 4402h
BX = file handle for device "HOOKROM$"
CX = 0004h
DS:DX -> DWORD buffer for address of hooked vector table (see below)
Return: CF clear if successful
DS:DX buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)

Format of hooked vector table entry:
Offset  Size    Description
00h  5 BYTEs   FAR jump to actual interrupt handler
(end of table if first byte is not EAh)
05h    BYTE    interrupt vector number

See also: 214402

214402 - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE