Int 68 Fn 03  - Appc/pc - Get Allocate                                     [N]

   AH = 03h subfn 2800h
   DS:DX -> control block (see below)

Return: control block updated

Format of control block:
Offset Size    Description
 00h 12 BYTEs  reserved
 0Ch   WORD    2800h (verb "Get ALLOCATE")
 0Eh  6 BYTEs  00h
 14h   DWORD   (big-endian) return code (see AH=01h/SF=1B00h)
 18h   WORD    00h
 1Ah  8 BYTEs  (big-endian) logical unit ID
 22h   BYTE    type (00h dequeue, 01h test)
 23h   DWORD   pointer to CREATE_TP record