INT 15,91 - Interrupt Complete

	AH = 91h

	on return:
	CF = 0 if successful
	   = 1 if error
	AH = when CF set, 80h for PC & PCjr, 86h for XT (BIOS 11/8/82)
	AL = type code:
	   = 00  disk
	   = 01  diskette
	   = 02  keyboard
	   = 03  pointing device
	   = 80  network (ES:BX = NCB)
	   = FC  fixed disk reset (PS/2)
	   = FD  diskette motor start
	   = FE  printer

	- should not be used by applications software
	- used by the BIOS to indicate device interrupt is complete
	- used for multitasking OS development