INT 14 - COURIERS.COM - CHECK IF PORTIBM PC Portable (uses same BIOS as XT) BUSY
	AH = 81h
	AL = port number (1-4)
Return: AH = status
	    00h port available
	    01h port exists but already in use
	    02h port nonexistent
Program: COURIERS is a TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user.  The name comes from the name of the DOS function call used to remain in memory after termination. utility by PCIBM PC Magazine
SeeAlso: AH=83h,AH=8Dh
                                                                                

INT 14 - COMM-DRV - EXTENDED INITIALIZATION                                     
	AH = 81h
	BX:DI -> port control block (see #00367)
	DX = port number
Return: AH = line status register (see #00304)
	    error if bit 7 set
	AL = modem status register (see #00305)
Program: COMM-DRV is a universal serial communications driver by Willies'
	  Computer Software Company, which supports standard INT 14 and
	  FOSSIL(Fido/Opus/Seadog Standard Interface Layer)  A standardized API for performing serial I/O, originally used by the Fido and Opus bulletin- board software and Seadog bulletin-board mailer, but now in wider use. calls as well as its own interfaces
Note:	AX=8001h should be called first to fill in the port control block
SeeAlso: AH=00h,AX=8001h,AH=82h"COMM-DRV",AH=86h"COMM-DRV"


Format of COMM-DRV port control block:
Offset	Type	Description	(Table 00367)
 00h	WORD	port IO address
 02h	WORD	port IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated.
 04h	WORD	baud rate
 06h	WORD	parity
 08h	WORD	data bits
 0Ah	WORD	stop bits
 0Ch	WORD	break status (0000h off)
 0Eh	WORD	flow control protocol
 10h	BYTE	input block
 11h	BYTE	output block
 12h	WORD	low threshold
 14h	WORD	high threshold
 16h	WORD	segment of buffer
 18h	WORD	offset of buffer
 1Ah	WORD	input buffer length
 1Ch	WORD	output buffer length
 1Eh	BYTE	auxiliary address
 1Fh	BYTE	spare
 20h  4 WORDs	spares