INT 13,C - Seek to Cylinder (XT & newer)

	AH = 0C
	CH = low order byte of cylinder number (see below)
	CL = high order byte of cylinder number (see below)
	DH = head number (0-15)
	DL = fixed drive number (80h=drive 0, 81h=drive 1)


	on return:
	AH = status  (see INT 13,STATUS)
	CF = 0 if successful
	   = 1 if error


	- many good programming references indicate this function is only
	  available on the AT, PS/2 and later systems, but all hard disk
	  systems since the XT have this function available
	- notice that CX is in reverse byte format similar to the way data
	  is stored in memory and reverse of normal register storage
	- only the disk number is checked for validity
	- the parameters in CX change depending on the number of cylinders;
	  the track/cylinder number is a 10 bit value taken from the 2 high
	  order bits of CL and the 8 bits in CH (low order 8 bits of track):

	  |F|E|D|C|B|A|9|8|7|6|5-0|  CX
	   | | | | | | | | | |	`-----	unused
	   | | | | | | | | `---------  high order 2 bits of track number
	   `------------------------  low order 8 bits of track number