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

entry   AH      44h 

	AL      00h     Get Device Information (from DX) 

			BX      file or device handle 

			return	DX	device info

			                If bit 7 set: (character device) 

			                   bit 0: console input device 

			                       1: console output device 

			                       2: NUL device 

			                       3: CLOCK$ device 

			                       4: device is special 

			                       5: binary (raw) mode 

			                       6: not EOF 

			                      12: network device (DOS 3.x) 

			                      14: can process IOCTL control 

			                          strings (func 2-5) 

					If bit 7 clear: (file)

			                   bits 0-5: block device number 

			                        6: file has not been written 

			                       12: Network device (DOS 3.x) 

			                       15: file is remote (DOS 3.x) 




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

entry   AH      44h 

		00h	Get Device Information (from DX)


note This function can be used to detect input and output redirection. Since

     the handle for STDOUT is always 1, if after calling Int 21 with AX=4400h

     and BX=0001h, the character device bit (bit 7) and the console output

     device bit (bit 1) are set in DX, anything sent to STDOUT will appear on

     the screen. If bit 7 is clear, we know output is being redirected to a

     file. If bit 1 is zero, the redirection is to another device.

See also:

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