INT 17 - PC Magazine PCSpool - GET CONTROL BLOCK ADDRESS
        AH = C0h
        DX = printer port (0-3)
Return: ES:BX -> control block (see below)

Format of control block:
Offset  Size    Description
 00h    WORD    printer number
 02h    WORD    address of printer status port
 04h    WORD    number of first record in queue
 06h    WORD    number of last record in queue
 08h    DWORD   characters already printed
 0Ch    DWORD   number of characters remaining
 10h    DWORD   pointer to dequeue buffer
 14h    DWORD   previous count of characters printed
 18h    DWORD   number of clock ticks taken to print them
 1Ch    WORD    offset of next character to output
 1Eh    WORD    offset of next character to print
 20h    WORD    pointer to spooling queue record
 22h    BYTE    current spooling status
 23h    BYTE    current printer status:
                00h OK
                01h not ready
                02h paused with message
                03h paused
                04h initializing
                FEh non-existent port
                FFh not spooled
 24h    BYTE    current control record type
 25h    WORD    observed printer speed
 27h    WORD    characters to print per service
 29h    BYTE    01h if disk write needed
 2Ah    BYTE    01h if queued data should be flushed
 2Bh    BYTE    01h to update cps status