TC: int ioctl( int handle, int cmd [, void *argdx, int argcx] )

	- prototype in io.h

	- direct interface to  INT 21,44  (IOCTL)
	- cmd = 0  get device information
		1  set device information (in argdx)
		2  read argcx bytes into addr given by argdx
		3  write argcx bytes from addr given by argdx
		4  same as 2, but handle treated as drive (0=def.,1=A)
		5  same as 3, but handle treated as drive (0=def.,1=A)
		6  get input status
		7  get output status
		8  test removability (DOS 3.x)
		11 set sharing conflict retry count (DOS 3.x)
	- cmd = 0,1; returns device information (DX of IOCTL call)
	- cmd = 2-5; returns count of bytes transferred
	- cmd = 6,7; returns device status
	- returns -1 on error & errno = EINVAL, EBADF, or EINVDAT
	- no corresponding function in MS C