Function  44h	 I/O Control for Devices (IOCTL)  Get or Set Device Information

entry   AH      44h 

	AL	0Dh	Block Device Request (DOS 3.3+)

			BL      drive number (0=default) 

			CH      major subfunction 

			CL      minor subfunction 

			        40h set device parameters 

			        41h write logical device track 

			        42h format and verify logical device track 

			        60h get device parameters 

			        61h read logical device track 

			        62h verify logical device track 

			DS:DX   pointer to parameter block