MEM 0040h:0004h - BASE I/O ADDRESS OF THIRD SERIAL I/O PORTIBM PC Portable (uses same BIOS as XT)
Size:	WORD
Notes:	the BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. sets this word to zero if is unable to find more than two
	  serial ports at the addresses it is programmed to check at boot
	Under DR-OpenDOS 7.02+ this setting can be changed with the
	  undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.).	 Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated. CONFIG.SYS COM3=[port_address|logical_no][,[timeout]]
	  directive, whereby port_address = 200h..3F8h, logical_no = 0 or 1..4,
	  timeout=0..255 (default 1).
SeeAlso: MEM 0040h:0000h,MEM 0040h:0002h,MEM 0040h:0006h,MEM 0040h:000Ch
SeeAlso: MEM 0040h:007Eh,PORTIBM PC Portable (uses same BIOS as XT) 03E8h"SERIAL"