INT 15 - OS HOOK - DEVICE BUSY (ATIBM PC AT,PSIBM PS/2, any model)
	AH = 90h
	AL = device type (see #00507)
	ES:BX -> request block for type codes 80h through BFh
	CF clear
Return: CF set if wait time satisfied
	CF clear if driver must perform wait
	    AH = 00h
Notes:	type codes are allocated as follows:
	  00-7F non-reentrant devices; OS must arbitrate access
	  80-BF reentrant devices; ES:BX points to a unique control block
	  C0-FF wait-only calls, no complementary INT 15/AH=91h call
	floppy and hard disk BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. code uses this call to implement a timeout;
	  for device types 00h and 01h, a return of CF set means that the
	  timeout expired before the disk responded.
	this function should be hooked by a multitasker to allow other tasks
	  to execute while the BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. is waiting for I/O completion; the default
	  handler merely returns with AH=00h and CF clear
SeeAlso: AH=91h,INT 13/AH=00h,INT 17/AH=00h,INT 1A/AH=83h


(Table 00507)
Values for device type:
 00h	disk
 01h	diskette
 02h	keyboard
 03h	PS/2IBM PS/2, any model pointing device
 21h	waiting for keyboard input (Phoenix BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly.)
 80h	network
 FBh	digital sound (Tandy)
 FCh	disk reset (PSIBM PS/2, any model)
 FDh	diskette motor start
 FEh	printer