/* A block io vector is a list of 3 driver addresses for
	* one major device: an open, close, and strategy routine.
	* Biosw is an an array of such vectors indexed by major
	* device numbers.
	*/
struct biovec
	{
	int  (* open )();
	int  (* close)();
	int  (* strat)();
	}
	biosw[];

	/*
	 * Device names for diagnostics
	 */
char *devname[];

	/*
	 * Convention: major device 0 is reserved for NODEV
	 */
#define NODEV	0

       /*
	* Character device switch
	*/
struct ciovec
	{
	int  (* open )();
	int  (* close)();
	int  (* read )();
	int  (* write)();
	int  (* mode )();
	}
	ciosw[];

	/*
	 * Macros for accessing the major and minor
	 * device numbers.
	 */
#define minor(dev)	((dev) & 0377)
#define major(dev)	((unsigned)(dev) >> 8)

       /*
	* Globals initialized in con.c
	*/
UINT	nbdev;		/* number of block devices */
UINT	ncdev;		/* number of character devices */
UINT	rootdev;	/* device number of root device */
UINT	swapdev;	/* device number of swap device */
UINT	swapsize;	/* number of swap blocks */
UINT	swapaddr;	/* number of first swap block */
			/* Note: if swapdev == rootdev, then */
			/* swapaddr is set to rootdev's fsize */