INT 21 - PenDOS PENDEV.SYS - ???

	AX = 4403h
	BX = file handle for device "$$PENDOS" or "$$PD_REG"
	CX = size of buffer
	DS:DX -> buffer containing ???
Return: CF clear if successful
	    buffer filled
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Program: A limited version of PenDOS by Communication Intelligence Corporation,
	  which provides pen capability to keyboard-based programs, is bundled
	  with IBM DOS 6.1
Note:	this call sets the WORD at offset 1Ah into the device driver request
	  header used to call the driver to 0000h.
SeeAlso: AX=4402h"PENDEV.SYS"