05H and 40H (BX=4) write data to PRN           ASCII Control Codes      
3301H notice Ctrl+Break during PRN output      Epson/IBM Printer Codes  
4407H get output status (check for busy)                                
440aH see if PRN is on a remote server
440cH 45H set retry iteration count

5e02H set network printer setup
5e03H query network printer setup

INT 24H Critical Error (get control on printer error)
INT 2fH 01xxH Print.Exe spooler services

INT 17H BIOS printer services

INT 05H Print screen
INT 0dH and INT 0fH LPTn IRQ handlers
                                                                              

Printer Functions